Mount Saint Helens Living Laboratory Curriculum

Mt St Helens

This curriculum is designed for grade levels 4-8. Adaption and adjustment is encouraged for grade levels 9-12.

The Mount St. Helens Monument has adapted some of the lessons for use at all levels.

The first three links on the right (Human Responses, Earth Windows, and Disturbance Ecology) below contain curriculum lessons. The last two links are supplemental and are linked from within the lessons when they are needed.


Human Responses- Human

Earth Windows- Geologic

Disturbance Ecology- Biologic

Instructional Strategies

Classroom Supplements


Human Responses

Mt St Helens 2004


Human Responses looks at the eruption from a human reaction point of view. View the links on the right to go through the instructional activities. 

Vulcan's Vocabulary

Goal: To provide definitions of words related to geologic and volcanic processes, as background for lessons to follow.

Objectives: Students will


  1. Complete vocabulary worksheets using Glossary of Volcanic and Geologic Terms and other resources;
  2. Collaboratively prepare for a Vocabulary quiz;
  3. Learn some useful mnemonic devices using The Magic of Metaphor.

Summary: Students are assigned to groups, and each member is assigned some of the words on the handout, Vulcan's Vocabulary Worksheet, to look up and prepare definitions for. Each student then teaches, using helpful mnemonic devices, his/her list of words to the rest of the group. Students study cooperatively for a vocabulary quiz over the handout list.

Content Areas: Science, language arts, study skills

Materials Needed:


Instructional Sequence: 

  1. Conduct whole-class discussion of memory and mnemonics. The Magic of Metaphor, page 4, "Memory Aids " provides a guide to using metaphor and simile as mnemonic devices. Provide further examples, illustrations, memory aids suggested by you and by students. Depending upon student readiness, you may wish to precede this lesson with a practice exercise using more familiar words, and/or study memory and recall/retrieval skills in depth.


  2. Assign students to heterogeneous groups of 5-7 members each. Provide copies of Vulcan's Vocabulary. Instruct groups to assign approximately equal shares of the list to all members.


  3. During class time or as homework, have each student prepare a definition for each assigned word, following these guidelines:


    • a. Find a definition for the term in resources provided.
    • b. Look up any words in the definition that are unfamiliar to you.
    • c. Rewrite the definition using your own words.
    • d. Include in your definition at least one of the memory aids discussed in class, or your own tip for remembering it.


  4. Return students to groups, where they will take turns providing definitions and suggesting ways for remembering them.


  5. When teammates have finished teaching each other, set up review groups or tournament teams per Cooperative Learning, Instructional Strategies folder.


  6. In this case, it is recommended that students receive a grade for group, rather than individual, performance on the quiz to follow this review activity. This will help teammates take responsibility for making sure that no member is unprepared for the quiz -- "No one is ready until we're all ready!"




    1. Older students in a geology classroom or major unit may be assigned advanced vocabulary work using worksheet form of Glossary of Volcanic and Geologic Terms.

A Place in Time

Goal: To familiarize students with an eruptive history and related world events, and impart a sense of the immensity of geological time.

Objectives: Students will


  1. Construct a personal history timeline
  2. Conceptualize a relationship between human historical events and events in natural history
  3. Apply memory aids to the task of learning dates and names of eruptive periods
  4. Conduct research in cooperative learning groups
  5. Construct a timeline of eruptive history at Mount St. Helens


Key Concepts: Study of eruptive history yields important understandings of earth's formation, present volcanic activity, and what the future may bring.

Summary: Students learn about timelines by creating their own, then are introduced to the major eruptive periods of Mount St. Helens. In research teams, they place these periods in context with historical occurrences. Students are taught names and characteristics of each eruptive period, utilizing metaphor and other aids to memory. (Vulcan's Vocabulary will help acquaint students with memory aids.)

Content Areas: History, social studies, science, math, study skills

Materials Needed: Handout:

Evaluation: Quiz students by having them record on handout the name and dates of each period, one characteristic feature of the period, and one major world event that occurred during that period.

Instructional Sequence:


  1. For opening discussion, focus on students' memories of their own important life events: "What kinds of events stand out in your mind?" (Brainstorm and list on board: first step, first day of school, learning to ride a bike, going to summer camp, etc.) "Do you often forget when, exactly, they happened?" "Does it help to remember them in relation to other events (holidays, birthdays, etc.)? "Do you recall them in mental pictures?" Extend by having students brainstorm likely future events up to the age of fifty (getting a driver's license, going to college, beginning careers, getting married, births of children and grandchildren, etc.)


  2. Present the concept of timelines.


  3. Provide drawing paper and colored markers or crayons. Establish a scale (for example, one inch on the paper may equal five years; or each student may be given a 10-inch length of string and pieces of masking tape to be used as labels and attached to string at measured intervals.) Direct students to create personal-history timelines. Any format should be acceptable, as long as it is titled, sequenced, and labeled with dates, and brief descriptions or illustrations of events, 


  4. Provide time for students to compare and contrast timelines and major life events.


  5. For contrast, show students a length of twine, with each inch standing for 100 years. Have them compute the number of years represented by the twine; talk about ways of solving this type of math problem. Explain that the length of twine represents Mount St. Helens' eruptive history, and show interval lengths for each of the major eruptive periods. (To give a sense of scale, attach a label to the twine for each of the eruptive periods, and display.)


  6. List eruptive periods and approximate dates on the chalkboard and assign each period to a "research team." Provide class time and materials, or time in the library, for teams to research major world events occurring during the period assigned to that team.


  7. Have teams select the six most important and/or interesting historical events of their period; prepare on butcher paper a timeline of their assigned period with labels, descriptions, illustrations, etc.; and prepare to share their timelines with the rest of the class. 


  8. Describe for students the important characteristics of each eruptive period. Have students generate metaphors for each. (For example, the Swift Creek period might be likened to repeated backfiring from a car; the Pine Creek's major pyroclastic flows likened to a melting ice-cream cone, etc.) Have students record the names of the periods and their corresponding metaphors on the Eruptive Periods Worksheet/Quiz handout. Help them recall from team reports some of the concurrent historical events for each period and make note of them on the handout.


  9. Encourage students to use different colors to distinguish the different eruptive periods, and to make illustrations of the metaphors associated with them, in their notes on the handout. Kinesthetic learners will also want to re-draw the timeline. Explain that these devices aid retention, and will help prepare students to be tested on names, dates and characteristics of the eruptive periods. Also discuss the powerful linking that is established when an unfamiliar idea is associated with a familiar mental image through metaphor. Explain that this technique, too, aids retention and recall. (Example: If the metaphor for the Smith Creek period is King Kong, because it is the largest period, then students might visualize King Kong building pyramids with the Egyptians during 2000 to 1300 B.C.) Other memory aids suggested in The Magic of Metaphor and Vulcan's Vocabulary may be useful here.

    Extension Activities:


    1. Have students illustrate their personal timelines using pictures from the family album, illustrations, objects. Display in classroom.


    2. Do the same with a "personal future timeline" in connection with a lesson on goal-setting.


    3. Write haiku or other poems about one of the eruptive periods.


    4. Research eruptive histories of other volcanoes (Hekla, Fiji, Tambora, Krakatoa, Pele, Vesuvius, etc.) Create timelines for these and compare/contrast with Mount St. Helens. (See also Life on a Fiery Planet).


    5. For math extension, have students design an eruptive-periods timeline to scale in millimeters.

Eruption Simulation

Goal: To help students understand a complex, cataclysmic natural phenomenon by breaking it down into sequenced and simultaneous components, cooperatively researching the nature of those components and their effects, and visualizing the whole through dramatic simulation.

Objectives: Students will


  1. Conduct research and teach each other about the eruption of Mount St. Helens, utilizing cooperative learning teams and expert groups.
  2. Be able to identify the major components of the eruption, their characteristics and their effects.
  3. Apply creative and critical thinking skills to reciprocally teach concepts and collaboratively plan a simulation.
  4. Simulate the eruption dramatically.
  5. Demonstrate their learning on a written test.


Key Concepts: Cataclysmic geological events have shaped and continue to alter our landscape and lifeforms.

Summary: In a series of small-group and whole-class discussions, individual research and reciprocal teaching exercises, students learn about six major components of the May 18, 1980 eruption of Mount St. Helens, and their effects on landscape and lifeforms. They then assume roles and plan for a dramatic simulation of the event, finally enacting it as an aid to visualization, thorough understanding, and retention of learning.

Content Areas: Science, language arts, drama

Materials Needed:


Instructional Strategies:

Articles in Classroom Supplements:

Evaluation: Have students complete Handout: Student Test/Evaluation to demonstrate learning. After in-class correcting, discuss with students their response to this kind of learning process and answer any remaining questions about the May 1980 eruption.

Note to Teacher: These activities may take from a few class sessions to two weeks or more, depending upon; the maturity and readiness of your students; modifications your students may require; time available for teaching cooperative learning and group process skills, use of descriptive language and imagery, etc.; steps you might choose to omit; quantity and quality of supplementary materials available. To help you estimate time required, review Handouts, Instructional Strategies, and Materials Needed.

Instructional Sequence:


  1. In whole-class discussion, help students identify what they already know about the May 18,1980, eruption of Mount St. Helens, and its environmental impact. Mindmap or cluster responses on chalkboard. (See Clustering/Mindmapping Techniques.) Explain that in this series of activities (over several class sessions, as time permits,) they will study the eruption in depth, including dramatizing the event so that it comes alive in their imaginations and is retained in their memories.


  2. In this or subsequent discussion, talk about acting. What kind of work must actors and actresses do to make the roles they play believable? What do they need to know about the characters and scenes they play? Explain that acting requires research, and that this activity will also begin with research.


  3. Explain the Learning-Team/Expert-Group process. Distribute Expert Group/Learning Team handout. Assign students to teams of six members each. Give brief oral definitions for the six components of the eruption. Direct groups to meet and assign one component to each member: precursory period, debris avalanche, lateral blast, vertical column, mudflow, pyroclastic flow. Note that every member is responsible for learning everything he/she can about the assigned component (area of expertise,) plus its particular impact/effect on the environment: natural landscape (rivers, trees, lakes, vegetation, etc.) and animal populations (people, elk, pocket gophers, deer, salamanders, insects, etc.)


  4. Distribute Expert Notes handout. Allow time for reading of supplementary materials provided and/or for library research, or assign as homework.


  5. Have expert groups meet to compare and share information, following steps outlined in Expert Group and Learning Team and keeping notes as directed on Expert Notes handout. Monitor group behaviors so that you can comment later, or give instruction, as needed, on contributing ideas, asking questions, listening, staying on task, etc. Review procedure and clarify instructions periodically.


  6. Hold a whole-class meeting after expert groups have completed their task, in order to 'debrief' the expert-group process: What problems surfaced? How did your group stick to the task, encourage participation, solve problems, resolve conflict? What do we need to do to improve our groupwork skills?


  7. Return students to their learning teams. Now each 'expert' has the task of informing the rest of his/her team about the eruption component he/she was assigned. Instruct students to follow the format on the handout. Encourage teammates to ask each other questions, and to be prepared to do additional research if necessary. Urge them to give their teammates as much detail as possible, and remind them to include any information they have found about their component's impact on landscape and lifeforms.


  8. For the simulation, select one or more members from each expert group, and assign to them the following roles needed in addition to assigned areas of expertise: narrator, trees (or other plant life, 2 to several,) pocket gophers (or other animal life, 2 to several). In whole-class discussion, have students provide suggestions for the narration, and for how trees and gophers will "behave" in the dramatization. Remaining members of expert groups will represent their assigned component of the eruption in the dramatization, planning together how they will move and behave in order to simulate that component's activity (see Simulation Plan handout.) The Eruption Simulation Storyboard may be distributed at this point (but not before) to aid in visualization. (Note: The narrator will require additional time and teacher-assistance to prepare for the simulation.)


  9. After Expert Groups have met and then shared their ideas with the whole class, complete planning for any special effects: props, scenery, sound effects, music, etc.


  10. "Rehearse" the simulation as many times as seems productive. Meet after each rehearsal to share suggestions for the narrator and participants. These rehearsals and discussions are very important, for they refine students' understanding of the eruptive event as well as illuminating "the whole" of the simulation. 


  11. If possible, invite another group to be audience for the final performance.

Life on a Fiery Planet

Life on a Fiery Planet


Goal: To illustrate for students effects on the evolution of human culture of volcanic events worldwide.

Objectives: Students will work cooperatively to:


  1. Apply knowledge of geologic processes gained in previous lessons about Mount St. Helens to volcanic events in other locations;


  2. Research the effects of one or more volcanoes other than Mount St. Helens on the physical landscape, human history, economy, technology, lifestyle, religion, politics, etc., of their geographical regions;


  3. Prepare a major small-group presentation in which findings are shared with the whole-class group.


Key Concepts: Physical changes in earth's landscape initiate responses that determine the community of lifeforms that can occupy that landscape, influencing not only plants and animals but the evolution of human life and culture.

Summary: Over several activity periods, teams of students select a group project for presentation to the large group, delegate research tasks among their members, conduct research on the geologic processes and effects on human evolution of one or more volcanoes in the country assigned to them, and cooperatively prepare their presentation.

Content Areas: Social studies, history, language arts, science

Materials Needed:


  1. Life on a Fiery Planet: Project Plan

Instructional Strategies:

  1. Cooperative Learning
  2. Eruption Simulation for Expert Group/Learning Team (instructions and handouts to be adapted for this activity)
  3. world maps and/or globes
  4. supplementary materials supplied by the teacher or available in the school library (suggestions follow lesson outline)

Instructional Sequence: 

  1. Have available or on the board the following list. Be prepared to help teams decide how many and which volcanoes they will study, depending upon materials available and number of students per group.


    • Group 1 -- United States: Augustine, Bogoslof, Katmai, Shisbaldin, Lassen Peak, Mount Baker, Mount Rainier, Kilauea, Mauna Loa
    • Group 2 -- Iceland: Askja, Grimsvotn, Heimaey, Hekla, Krafia, Laki, Surtsey
    • Group 3 -- Soviet Union: Bezymianny, Karymsky, Kiiuchevskoi, Tolbachik
    • Group 4 -- Indonesia: Agung, Dieng, Galunggung, Kawan Idgen, Kelut, Krakatau, Merapi, Papandajan, Peak of Ternate, Smuru, Tambora
    • Group 5 -- Japan: Asama, Aso, Bandai, Bayonnaise Rocks, Fuji, Oshima, Sakura-zima, Tarumai, Unzen, Usu
    • Group 6 -- Italy: Etna, Monte Nuovo, Stromboli, Vesuvius, Vulcano
    • Group 7 -- Costa Rica: Arenal, Irazu, Poas
    • Group 8 -- Ecuador: Cotopaxi, Guagua Pichincha, Reventador, Fernandina
    • Group 9 -- Nicaragua: Cerro Negro, Cosequina, Masaya


  2. Assign students to several small groups. (Number of teams depends upon size of class, and materials available, but 3 to 5 is optimal.) Distribute Life on a Fiery Planet, Project Plan.


  3. Assign to each group a country. (The volcanoes targeted for study may be chosen by teammates with teacher assistance, or teacher-assigned.)


  4. Explain that each student is responsible for a completed worksheet on one volcano, and for sharing everything he/she learned about that volcano with the rest of the team.

Instruct groups to select the kind of presentation they will prepare, from the following list of possible presentation designs, others proposed by the teacher, or their own, subject to teacher approval. (As an alternative, any one of the more comprehensive project designs could be assigned to all the groups.)

Suggested Presentation Designs:

  1. Videotape a newscast, written and performed as though one of your country's major volcanoes has just recently erupted. 
  2. Design a mural to illustrate changes a volcanic event in your country has created in human culture, physical landscape, climate and weather patterns, etc.
  3. Design a timeline that illustrates the eruptive history of your country's volcanoes.
  4. Role-play interviews with 'witnesses' to several of your country's volcanic events and their aftermaths.
  5. Write an epic poem from the perspective of a surviving witness to a the most devastating volcanic eruption your country has experienced.
  6. Based on what your group has learned about the history and predicted future of a presently dormant volcano in your country, plan a city to to be built in its vicinity. Consider such things as building construction, what kind of technologies will be important, how the economy will be sustained, transportation patterns, and evacuation plans in the event of another major eruption.
  7. Outline the history of a culture profoundly affected by volcanic activity in your country. Focus on those things that would be different had the volcano not been there (art, music, dance, housing, agriculture, religion, economic conditions, customs, etc.)

Attenborough, David, The Living Planet; (Little, Brown & Co., 1984)

Corcoran, Thom, Mount St. Helens: The Story Behind the Scenery (K. C. Publications, Inc., Post Office Box 14883, Las Vegas, NV 891144, 1984)

Decker, Robert and Decker, Barbara, Volcanoes (W.H. Freeman & Co., 1980)

The Making of a Continent (American Geological Institute, 4220 King Street, Alexandria, VA 22302) (companion volume to PBS series by same name) 

Earth: The Restless Planet and Living on Our Changing Planet (Karol Media, 22 Riverview Drive, Wayne, NJ 07470-3191)

The Earth Explored (Advanced) (PBS video series, 28-minute geology videos, call toll-free 1-800-424-9763)

Planet Earth (Time/Life Series, 1982) (series includes "Continents in Collision," "Earthquake," "Gemstones," "Glacier," "Ice Ages," and "Volcano")

Our Violent Earth (Advanced) (1982 National Geographic Society, Educational Services, Department 85, Washington D. C. 20036)

Volcanic Eruptions of 1980 at Mount St. Helens: The First 100 Days (Geological Survey Professional Paper 1249, USGS, Geologic Inquiries Group, 907 National Center, Reston, VA 22092, 1982)


Evacuating for a Volcano

Goal: To explore hazards associated with cataclysmic natural events, and human responses to them.

Objectives: Students will


  1. Work cooperatively in small groups to solve a problem
  2. Consider ways of minimizing risk and threats to human safety
  3. Identify behaviors appropriate in an emergency situation
  4. Plan an orderly, step-by-step process in a limited amount of time
  5. Evaluate their own group decision-making processes.

Concept: Cataclysmic events create threats to individual safety that must be analyzed and managed logically, methodically, and cooperatively.

Summary: Students imagine themselves staying for the weekend in a summer cabin near Mount St. Helens (or other volcanic site,) and having to quickly evacuate the area. Working in groups of three to six, they decide on the location of their cabin in relation to the mountain, and plan an evacuation procedure on a 30-minute timeline. Groups attempt to solve this problem cooperatively. Students then evaluate their groups' success, analyzing and discussing processes used to establish priorities, make plans and decisions, manage time and achieve consensus.

Content Areas: Social studies, language arts, science, group-process skills*

Materials Needed:


  1. Anywhere Recreation Area Map
  2. Evacuation Scenario
  3. film (optional) "This Place in Time: The Mount St. Helens Story"
  4. butcher paper
  5. marking pens

Instructional Strategies:

  1. Clustering/Mindmapping Techniques
  2. The Magic of Metaphor (especially p. 3, "Guided Fantasy.")


*Group's task may be simplified for younger students; for older students, it may be preceded or accompanied by specific instruction in such group-process skills as consensus-building, decision-making, conflict resolution, etc.

Instructional Sequence:

  1. Divide students into groups of three to six members each. Provide each group with one copy of Anywhere Recreation Area Map. Group is to begin by deciding upon the location of their summer cabin, listing at least three reasons for their choice. Emphasize that they must all agree on the location and the criteria for choosing it. Once they have decided, they should draw their cabin on the map.


  2. Ask students to imagine themselves in the Evacuation Scenario. Read it aloud to the class. (For dramatic effect, you may want to show the film or video version of "This Place in Time: The Mount St. Helens Story") 


  3. Explain that it is now 7:30 a.m., and the groups have only 30 minutes in which to plan their evacuation. They must decide upon a plan that uses the resources they have available, and gets them out of the area in the least possible time. Emphasize that every member of the group must agree to the plan. Their resources include:

    a. an all-terrain two-person vehicle
    b. a battery-operated am/fm radio
    c. three days' worth of food
    d. three fishing poles and a hunting knife
    e. three knapsacks
    f. a camp lantern
    g. map of Anywhere Recreation Area
    h. a deck of cards.


  4. It will be helpful to provide the groups with instruction in the following problem-solving process:

    a. Brainstorm members' thoughts and ideas about the evacuation, and list them on sheets of butcher paper.
    b. Decide on the three best ideas and discuss negative and positive aspects of each.
    c. Choose the best idea or combine ideas to arrive at the best option.
    d. Brainstorm ways to carry out the plan.
    e. Choose the best strategies, and assign roles and responsibilities.
    f. Write up a plan of action, consisting of steps on a timeline.

    (When students have agreed upon and completed the plan of action, they may consider themselves "evacuated." Have each group record the time it took them to complete the task.)


  5. After thirty minutes, find out which groups made it out in time and which did not. Record their times on the blackboard. Allow time for each group to share its plan. Encourage comments on the plans from other students.


  6. Have students discuss in their groups the following questions:

    a. What were your thoughts and feelings about this activity?
    b. What did you find difficult about it?
    c. How does this simulation compare to a real-life situation?
    d. How did your group resolve conflict?
    e. What kinds of behaviors are important in an emergency situation?
    f. What issues prevented or threatened to prevent your group's getting out in the time allowed?
    g. Choose one of these issues and brainstorm possible alternate solutions.


  7. Conduct a whole-class discussion. Provide opportunity for students to see how those in other groups made decisions, resolved conflicts, etc.


  8. Provide closure. Explain that volcanic activity can be seen as destructive when you think about its impact on the landscape, bridges, homes, highways, wildlife and people. However, as they continue this unit their study will focus on another side of volcanic eruptions: volcanic forces as part of a natural earth-building process.



  1. Provide original groups with butcher paper and colored marking pens. As a lead-in to further work with this unit, direct them to brainstorm what they already know about volcanoes and volcanic eruptions. If they are unsure of their information, or as they have questions, have them circle those items in their brainstorming list. After ten minutes or so, have groups share with the class their questions and needs for additional information about the topic.


  2. Post a composite list of questions in the classroom, so that you can refer back to them as the unit progresses. Unanswered questions can also be the starting points for students' final independent projects.

Looking back to 1980

Goal: To provide students with opportunity to speculate, draw inferences, and form conclusions from information they have collected.

Objectives: Students will

  1. Engage in a guided-imagery exercise designed to stimulate motivation for a writing assignment


  2. Use clustering/mindmapping techniques to generate ideas, graphically represent inferences, and organize conclusions for a written report


  3. Write a report that presents conclusions the writer has reached, and facts substantiating those conclusions


Key Concepts: Inferences about life in other cultures, other times, may be drawn from excavated artifacts.

Summary: The teacher uses guided imagery to facilitate students' imagining themselves to be 25th-Century archaeologists, excavating artifacts from the site of a volcano active in the 1980's. Students then write a report detailing the inferences they have drawn and conclusions they have reached about human culture at the time of the eruption, substantiated by their analyses of those artifacts. (Note that this activity may refer to an eruption at any imaginary or actual volcanic site.)

Content Areas: Writing, social studies, archaeology, anthropology, history

Materials Needed:

  1. Paper and pencil

Instructional Strategies:

  1. Clustering/Mindmapping
  2. Peer Editing
  3. The Magic of Metaphor


Evaluation: Establish criteria (depending upon what you have chosen to emphasize) for teacher or self-evaluation. These might include such questions as:

  1. Does each idea-cluster have at least three major sub-topics?
  2. Do the clusters contain descriptive, colorful language?
  3. Are each of the conclusions reached in the report substantiated by two or more 'facts?'
  4. Is creativity and originality exhibited in the final report?
  5. Has care been taken in the final revision/draft to correct mechanical errors?
  6. Has the final report been read by at least two peer-editors?


Instructional Sequence:  

  1. Introduce this activity with your own guided imagery, or read the following:

    You are an archaeologist from the 25th Century. You have just received an exciting new assignment. You are to direct the excavation of an ancient mudflow created by the eruption of (Mount St. Helens more than 400 years ago). Shortly after your arrival at the site, the digging begins. Day after day for two weeks, you and your crew carefully excavate layer upon layer of earth, silt and rocks, frequently coming upon huge boulders which can be moved only with the power and leverage provided by special heavy equipment. As one of these boulders is being moved, you sense that you are on the verge of great discoveries, for at its base you see an unfamiliar, shiny object that glistens and twinkles in the sun's rays. You pick up a small ring of metal unlike anything you have ever seen or read about. You call excitedly to other members of your crew, who, in just a few hours, help you unearth an astonishing collection of artifacts. A few of them are recognizable as items you've learned about in classes in history and anthropology. But others are completely unfamiliar: the object that first caught your eye -- the aluminum pop-top from a soft drink can -- and a pocket calculator, a rubber raft, a steel-belted radial tire, the rusted hulk of a Volkswagen, a digital watch, a leather belt, a plastic 'zip-lock' bag and inside the bag, perfectly preserved, a copy of TV Guide. For the next few minutes, quietly focus your mind's eye on these objects. What do they tell you about human life in (Washington State at the time of the Mount St. Helens eruption)? (Allow 2-3 minutes for silent reflection.)


  2. Conduct a discussion about the guided imagery, and students' individual imaginings about the artifacts unearthed. To encourage imaginative speculation, remind students to think in terms of a 25th-Century perspective: the objects unearthed at the site are not in use in their own day, and are foreign to them.


  3. As students contribute, note on the chalkboard key words, phrases, and images mentioned. (Use the "Clustering" method.) At the end of the discussion, give a brief explanation of the clustering method which you have just modeled on the board, or take time here to explicitly teach it as a study and note-taking skill.


  4. Now direct your students to write their own lists of several of the items excavated in the guided imagery. Tell them to select the items they would find most interesting to study if they were archaeologists of the future. Explain that they will use these lists to generate ideas for a report they will write, on life in (Washington State) at the time of the eruption. 


  5. As a whole class or in small groups, discuss the difference between an inference and a conclusion. What might an archaeologist infer about our culture from these artifacts? What might they conclude?


  6. Referring to the model on the board, ask students to "cluster" their ideas, key words and images around each of the items on their lists. Establish a minimum number of sub-topics per item and encourage the use of colorful descriptive language. (Circulate to assist with this if the technique is new to them.)


  7. In the next one or two class periods, help students to organize their clustered inferences into the final conclusions they will report in writing. They might work individually or in pairs. (Small-group editing, with each student reading aloud a draft of the report and getting feedback from peers, would be useful here. See:  Peer Editing.) 


  8. Have students finalize reports according to the standards for written work established for your class.



  1. Hold an "archaeologists' forum" in which individual students will share their inferences and conclusions about life in (Washington State) in 1980. Encourage students to take issue with their classmates' conclusions, and express opinions of their own, in a courteous and respectful way. This activity could then lead to debates about the various conclusions students have reached regarding one or more of the objects excavated.


  2. Conduct a survey, in which students ask people they know to identify the object(s) in our present environment that would be mostly likely to perplex people living in the 25th Century. Tabulate the results and share findings in further class discussion.

Mountain Myths

Goal: To help students understand why, in the absence of scientific understanding, human beings have created mythology to explain natural phenomena, and to encourage an appreciation of this literature.

Objectives: Students will

  1. Become familiar with Native American myths and legends created to explain volcanic activity


  2. Apply the clustering, writing process and peer-editing techniques to the writing of an original myth about Mount St. Helens


  3. Illustrate an original myth.


Key Concepts: To explain natural phenomena, various cultures have created myths in which natural phenomena and features in the environment are assigned human-like personalities and qualities. 

Summary: Students explore the function of myths. Imagining themselves to be members of the Cowlitz (or other) Indian tribe, students do a practice exercise in which, as a group, they write a simple myth to explain rumblings from Mount St. Helens. After reading a sampling of Northwest Native American myths on the subject, students analyze the various identities that have been assigned, in past times, to mountains and other natural features. After brainstorming other possible identities, students select and develop a characterization, and create an original storyline, employing a clustering technique, a writing/rewriting process, and peer-editing strategies. Students illustrate and prepare their myths for an audience.

Content Areas: Composition, literature, science, history, anthropology, geography, art

Materials Needed:


Instructional Strategies: 


  • Paper and pencils
  • fabric crayons
  • fabric, t-shirts (optional) 


Evaluation: Evaluation of students' myths should relate to writing skills currently being taught in class, as well as effort, originality and creativity displayed. 

Instructional Sequence:

  1. Ask students to imagine themselves members of a Native American tribe living within sight of a volcano, before the white man came. The mountain, quiet and serenely beautiful for as long as anyone can remember, has recently begun to change. Occasionally, light-gray puffs that seem different from other clouds have been appearing around the peak. Strange rumblings that seem to come from deep within the earth have been heard. Nothing in the legends and lore of the tribe explains these occurrences.


  2. Ask students to respond, individually or in small groups, to such questions as:
    • How would the you be likely to feel about these developments? (list likely feelings)
    • What would you have to do in order to feel comfortable and secure?
    • How might you and your companions make sense of or explain what was happening to your familiar natural environment? (list some possible explanations)


  3. Allow time for brainstorming and discussion. Together, select the best idea and write a brief narrative on the board.


  4. Compare and contrast students' ideas with the Cowlitz Indians' legend that tells of a time when Mount Rainier had two wives, Mount Adams and Mount St. Helens, and of an argument between the wives in which Mount St. Helens became jealous, "blew her top," and then knocked off Mount Rainier's head! (The Cowlitz called Mount St. Helens "Lavelatla," or "smoking mountain.") Note that such accounts help us reconstruct eruptive history.


  5. Share other examples of early cultures' explanations for eruptive and earthquake activity; for examples:
    • Before Magellan sailed, one common belief was that the earth was flat and held up by two elephants standing on a turtle's back. When the earth shook, it was because the creatures supporting it were moving about.
    • Others believed that giant whales, slapping their immense tails against the ocean floor, caused the earth to tremble.
    • Some believed such activity was evidence that sea monsters were fighting.
    • The ancient Romans believed that Vulcan, god of fire and metalworking, had a blacksmith shop a mountain on an island near Sicily, named Vulcano. This is where the word 'volcano' came from.


  6. Read or provide copies to students of handout, Native American Myths.


  7. Identify common characteristics of identities assigned to mountains by Native Americans (ex: Mount St. Helens was always a person, rather than an animal; always had a "reason" for erupting.) Have students brainstorm other possible identities for a volcano, either human or animal. Refer back to ideas generated in step 1. Instruct students to select an identity to write about.


  8. Allow time for students to 'cluster' on paper the words and phrases they want to associate with their chosen identity before, during, and after the eruption. Students will then list in an 8-step sequence what happens to their identify from before to after the eruption. Encourage them to include colorful adverbs and adjectives, additional 'characters' (other natural features,) and action verbs. This will provide a framework for their writing an original myth about the eruption of Mount St. Helens.


  9. Arrange for an audience to which students may target their work. (For example, students might work in partners to simplify the language of their myths, condense them to one page, create a full-page illustration for each, and bind them in a booklet for younger children; or study the art of storytelling, and arrange to read their original myths aloud to each other or another group.) 


  10. Allow class time for writing the first drafts of original myths and/or for the revision process using peer editing groups (See: Peer Editing.)



  1. Use fabric crayons to make illustrations depicting students' myths, to be transferred onto t-shirts, or onto fabric squares that may be used to make a class quilt.


  2. In pairs, have students take turns playing the role of a) interviewer, and b) character from a student myth, using questions prepared in advance. Record or videotape the interviews.

Human Response Handouts

This section is designed to supplement the lessons in the Earth Windows section of A Living Laboratory: Volcanoes.

The links on the right are hand outs used in this section of the lab.

Learning Team

First Meeting:
In your Learning Team's first meeting, decide which components of the eruption each of you will become "expert" in:

Team Member / Area of Expertise

1. __________________________________ The precursory period
2. __________________________________ Pyroclastic Flow
3. __________________________________ Rock debris avalanche
4. __________________________________ Lateral blast
5. __________________________________ Lahars
6. __________________________________ Vertical column

As the assigned "experts," you and your teammates will now take turns leading a discussion, in which you will find out what your teammates already know or believe about your assigned topic, and what they want to know. List these things in "Expert Notes," Sections 1 and 2. As you do your research and share findings with your Expert Group, try to find answers to your Learning Teammates' questions.


** Independent Research and Expert-Group Meeting(s) **

Second Meeting:
Taking turns, each member will teach the rest of the team about his/her area of expertise. Teammates should keep notes, including any helpful metaphors or other memory aids, illustrations and diagrams, key words and phrases. Allow time for each expert to answer questions from the group and discuss areas where more information is needed.

Third Meeting:
After the whole class enacts the eruption in a dramatic simulation, a final Learning Team meeting will be held. The purpose this time is:

  1. to have experts answer any remaining questions
  2. to make sure that every member of the team is ready for a test on the material
  3. to wish each other "Good Luck!"

Expert Group

  1. What are the most important things to know about your area of expertise? Take turns adding one item at a time to a list. Share what you have learned about each item. If you have nothing new to add, let a groupmate take your turn. Keep careful notes in your "Expert Notes" handout section 5, about new things you learn from your groupmates. In Section 6, list everything about your topic that you want your Learning Team to learn.


  2. Check Section 2 in your "Expert Notes." Have all your Learning Team's questions been answered? If not, see if your Expert Groupmates can help. 


  3. How will you teach these things? Discuss with your groupmates each of the methods below. Choose the ones you want to use when you teach your Learning Team. Record them in "Expert Notes," Section 7.


      A. Metaphors: Take turns describing your assigned topic in terms of familiar images. (For example, a mountain before an eruption might be likened to a vanilla ice cream cone. After the eruption, it might be compared to the cone after the ice cream has fallen out on the ground!) Choose the metaphor you like best, record it in "Expert Notes" Section 7A, and use it to help your Learning Teammates understand your topic.

      B. Visual Aids: Draw a diagram or illustration, or choose an object, that will help you show the idea you want to teach. Take turns suggesting ideas or sharing drawings. Select the visual aid you want to use when teaching your Learning Team, and record it in "Expert Notes" section 7B.

      C. Descriptive Words and Phrases: In your Expert Group, brainstorm colorful adjectives, adverbs and action verbs that will help you describe your topic to your Learning Team. Select some you like and record in "Expert Notes" section 7C.

      D. Learning Activities: Try to think of ways your Learning Team can participate actively while you teach them. Share ideas for games, work-sheets, puzzles, quizzes, simulations, etc., that you might use with your Learning Team. Record the best ideas in "Expert Notes" section 7D.


    6. Outline in "Expert Notes" Section 8, your complete, step-by-step plan for teaching your Learning Team about your area of expertise.

'Expert' Notes

To become an "Expert:"

  • Find out what your Learning Teammates already know and what they want to know about your topic
  • Read, thoroughly, all available material on your topic
  • Participate actively in Expert Group meetings
  • Keep careful notes on this handout from your reading and your meetings with your Expert Group, including as much detail as possible, in your own words. Refer to the Expert Grouphandout for help with this form.


Think about the following:

  1. Members of my group already know or believe the following about (your topic):
  2. Members of my group are curious or want to know the following about (your topic):
  3. Things I've learned from my research and reading (show your sources:)
  4. Questions I need to ask other members of my Expert Group:
  5. New things I've learned in my Expert Group (notes from discussions:)
  6. Things I want my Learning Team to learn from me:
  7. How I plan to teach them:
    • Metaphors:
    • Visuals (diagram, picture, model:)
    • Descriptive Adjectives, Adverbs and Verbs:
    • Learning Activities:
  8. My Complete Teaching Plan:

Student/Test Evaluation

1. List events that are the major components of the Mount St. Helens eruption of May 18, 1980. Next to the component, write a brief description or key phrase that describes it.


		Event:				Description:


    A. __Precursory Period__________________Earthquakes occur and bulge grows__



    B. _________________________________________________________________



    C. _________________________________________________________________



    D. _________________________________________________________________



    E. _________________________________________________________________



    F. _________________________________________________________________



2. In complete paragraphs, describe how the May 18, 1980, eruption affected the environment. Give specific examples in each category, below:

    A. Plants and trees:

    B. Animals, including humans:


    C. Landscape:


    D. Manmade structures:

3. List two or more things you have learned in this unit about cooperative learning:

4. List things that you, personally, might do to improve your performance as a member of a group:

5. Tell what you like best about this activity, and why.

6. Tell what you like least about this activity, and why:


Simulation Plan

To prepare for your dramatic simulation of the Mount St. Helens eruption of May 18, 1980, take a few minutes to read, think about, and jot some notes on this handout. Then, meet with your Expert Group (lateral blast, pyroclastic flowlahar, etc.) or Role Group (new groups assigned to the roles of trees and pocket gophers) to share members' ideas and plan your part in the dramatic action.

1. Brainstorm alone, and then with your group, about the characteristics of your assigned role. To help with this, ask yourself . . . If this role (a pyroclastic flow, a tree, a lateral blast, etc.) were a person, it would have these characteristics:


    Physical appearance:


    Speech patterns (volume, accent, fast/slow, etc.):






2. Brainstorm alone, and then with your group, about the way your assigned role "acts:"


    It moves like . . . 


    It looks like . . . 


    It sounds like . . .


3. Write a description of the action of your assigned role, using ideas from 1 and 2.


4. Brainstorm all the different ways you and your group could dramatize this action. With your group, pick the best one. Make notes on it here.


5. Decide on a sequence. At what point in the eruption sequence does your role start its action? Stop its action? (You may refer to the "Eruption Storyboard" if your teacher provides it, or draw your own cartoon-like set of illustrations depicting stages in the eruption.) What will be your group's first move? Will different members do different things? Where in the 'stage' area will your part of the action take place?


6. Are there materials or props that would make your part of the dramatization more effective? Think about what you might do with the following. In your group, decide which ones (if any) you want to use and which members could provide them:



    Sound effects:




7. Appoint one member to report to the whole class on what your group has decided to do.

8. In whole-class discussion, you will talk about how your plan fits with those of the other groups, and in what order. Everyone must agree that your plan will work.

9. Finally, set the date, finish the preparations, apply the final touches, and . . . "Break a leg!"

Eruption Storyboard


Project Plan: "Life on a Fiery Planet"

Team Members:

_______________________________          _______________________________

_______________________________          _______________________________

_______________________________          _______________________________

_______________________________          _______________________________

Country: _________________________

Volcano: _________________________

Instructions: Using resource materials supplied by your teacher or found in your school library, research answers to the following questions about the volcano you have been assigned. Be prepared to share your answers with your teammates.

  1. Where does your volcano fit in the volcanic history of your country? Is it part of a chain of volcanoes? Is it the only volcano in its region? How does it compare to others in your country, in terms of age, dates of eruptive periods, kinds and magnitude of eruptions, etc.? How does it compare with other volcanoes in your country in terms of impact on the physical landscape? the country's geography? Human life and culture? What is its current status? Its predicted future?
  2. What types of human communities surround your assigned volcano? Are they rural? urban? What kinds of technology are available to them today? How do they make their living? Do they all speak the same language? Which cultural groups have been most affected by your mountain's eruptive history? How are they different/similar in lifestyle, religion, politics, economics, etc.?
  3. Of the cultural groups living in close proximity to it, which one best reflects the impact of its eruptive episodes? Where is evidence of that impact found? Is it evident in their art, literature, dance, music, religion, government, ways of making a living, styles of architecture, level of modernization, etc.?
  4. Did any of your mountain's past volcanic events have a global effect? Consider its possible effect on other parts of the world, due to changes in culture, disaster effects such as famine or plague, climate and weather, etc.
  5. Do the human communities that live close to your volcano appear to take into account the possibility of future cataclysmic events in their own backyards? Is the threat of future eruptions reflected in new technology? new land uses or management policies? monitoring and evacuation plans? protected areas like parks, preserves, monuments, study and recreation areas? religious beliefs? customs and folklore? new economic bases like mining or tourism?
  6. Make two lists below, one showing the direct and indirect negative effects of your mountain on nearby human communities, the other its benefits (direct and indirect.)


Negative Effects			Benefits

_____________________________          _____________________________

_____________________________          _____________________________

_____________________________          _____________________________

_____________________________          _____________________________


Native American Myths

Northwest Native American Myths

Native Americans of the Pacific Northwest watched eruptions of Mount St. Helens long before the explorers and settlers came. Early accounts of eruptions were handed down and explained by their legends, contributing to a rich tradition of oral history and myth.


From the Puyallup Tribes

According to the lore of these tribes, long ago a huge landslide of rocks roared into the Columbia River near Cascade Locks and eventually formed a natural stone bridge that spanned the river. The bridge came to be called Tamanawas Bridge, or Bridge of the Gods. In the center of the arch burned the only fire in the world, so of course the site was sacred to Native Americans. They came from north, south, west, and east to get embers for their own fires from the sacred fire.


A wrinkled old woman, Loowitlatkla ("Lady of Fire,") lived in the center of the arch, tending the fire. Loowit, as she was called, was so faithful in her task, and so kind to the Indians who came for fire, that she was noticed by the great chief Tyee Sahale. He had a gift he had given to very few others -- among them his sons Klickitat and Wyeast -- and he decided to offer this gift to Loowit as well. The gift he bestowed on Loowit was eternal life. But Loowit wept, because she did not want to live forever as an old woman.


Sahale could not take back the gift, but he told Loowit he could grant her one wish. Her wish, to be young and beautiful, was granted, and the fame of her wondrous beauty spread far and wide.


One day Wyeast came from the land of the Multnomahs in the south to see Loowit. Just as he arrived at Tamanawas Bridge, his brother Klickitat came thundering down from the north. Both brothers fell in love with Loowit, but she could not choose between them. Klickitat and Wyeast had a tremendous fight. They burned villages. Whole forests disappeared in flames.


Sahale watched all of this fury and became very angry. He frowned. He smote Tamanawas Bridge, and it fell in the river where it still boils in angry protest. He smote the three lovers, too; but, even as he punished them, he loved them. So, where each lover fell, he raised up a mighty mountain. Because Loowit was beautiful her mountain (St. Helens) was a symmetrical cone, dazzling white. Wyeast's mountain (Mount Hood) still lifts his head in pride. Klickitat , for all his rough ways, had a tender heart. As Mount Adams, he bends his head in sorrow, weeping to see the beautiful maiden Loowit wrapped in snow.


From the Yakima Tribes

Si Yett, meaning woman, is the Yakima Indian name for Mount St. Helens. According to legend, Si Yett was a beautiful white maiden placed on earth by the Great Spirit to protect the Bridge of the Gods on the Columbia River from the battling brothers, Mount Adams and Mount Hood.


From the Klickitat Tribes

Klickitat Indians tell of two braves, Pahto, (Mount Adams) and Wyeast (Mount Hood), who fought to win the affections of an ugly old hag, who had been turned into a beautiful maiden by the Great Spirit.


From the Cowlitz Tribes

Cowlitz Indian legends tell of a time when Mount Rainier had an argument with his two wives, Mount St. Helens and Mount Adams. Mount St. Helens became jealous, blew her top, and knocked the head off Mount Rainier. 


(Cowlitz Indians called Mount St. Helens "Lavelatla," which means "smoking mountain.")

Vulcan's Vocabulary Worksheet

Using complete sentences, define the following volcanic terms:

1. Andesite:

2. Ash:

3. Ashcloud:

4. Ashfall:

5. Ashflow:

6. Avalanche:

7. Basalt:

8. Composite Volcano:

9. Crater:

10. Dacite:

11. Debris Avalanche:

12. Dome:

13. Lahar:

14. Lava:

15. Lavaflow:

16. Magna:

17. Mudflow:

18. Phreatic eruption:

19. Pumice:

20. Pyroclastic:

21. Pyroclastic Flow:

22. Tephra:

Anywhere Recreation Area Map


Vulcan's Vocabulary Quiz

Define the following terms:

1. Composite volcano:

2. Magma:

3. Pyroclastic flow:

4. Dacite:

5. Conduit:

6. Tephra:

7. Basalt:

8. Lahar:

9. Phreatic Eruption:

Eruptive History Worksheet/Quiz

Name of Period Dates 
Memory Aid
World Event

Earth Windows


Earth Windows looks at the eruption from a geological point of view.



Ape Cave Exploration


Goal: To provide students with an understanding of lava-tube formation, and the geological and ecological features of the Ape Cave ecosytem.

Objectives: Student will demonstrate ability to:

  1. Describe how a lava tube forms.
  2. Recognize the niche occupied by several life-forms
  3. surviving in this specialized ecosystem.
  4. Locate, sketch and identify sources of five of Ape Cave's geological features.
  5. Appreciate the necessity of protecting such delicate ecological systems, taking proper safety precautions, and observing behavioral rules during their small-group exploration of Ape Cave.


Key Concepts: A lava flow may travel great distances, creating unique geological features and ecosystems because of its self-insulating properties. Lava tubes represent a fragile, specialized habitat requiring care and respect on the part of huma n visitors.

Summary: Students simulate the formation of Ape Cave, in order to better understand its construction. Students observe, illustrate and discuss geological features of this lava tube. The teacher provides instruction in preserving ecosystem balanc e, and the effects of human vandalism on Ape Cave.

Content Areas: Geology, speleology, biology, ecology, environmental studies, art.

Materials Needed:



Needed supplies and equipment:

  • lanterns
  • flashlights
  • jackets
  • hats
  • sturdy shoes
  • trash bags for litter-collection

(A teacher/student ratio of 1:8 is advised for this field activity.)

Evaluation: Participation in simulation activity, completion of Geological Features activity-sheet, appropriate conduct reflecting respect and appreciation.

Instructional Sequence:

  1. As you travel to Ape Cape, have students draw a cross-section of the bus, in order to practice this skill.


  2. Also on the bus, review key characteristics of a lava flow.


  3. Liken the bus to the magma chamber of Mount St. Helens, with the doors of the bus representing the vent through which lava was emitted.


  4. Point-out the "features" of the cave represented in the simulation (tube, skylights, breakdown, flow-through,) and discuss.


  5. Explain the Geological Features activity-sheet and give instructions for its completion.


  6. At the entrance to Ape Cave, discuss:


    • When it was formed.
    • Who discovered it, and how.
    • How the cave got its name.
    • Proper cave-exploration behavior: respect for all features, no running, quiet voices, lights on all times and kept out of people's eyes, remaining in groups of four.


  7. Divide class into "explorer groups" of four students each. Assign at least one adult per two groups of four. Send half the groups upslope (beneath stairs) for ten minutes, to identify and sketch the tube-in-tube, lavacicles, ceiling breakdown. Send the other half downslope for ten minutes to identify and sketch flow-mark s, wall breakdown. Reverse the groups' locations and assignments for the second ten minutes.


  8. Gather groups together at the bottom of the stairs to share what they have found. Assign to each group a geological feature, which they will discuss among themselves for a few minutes and then present to the whole class, or on which they will later h ave an opportunity to become "experts" for a school-site presentation.


  9. To conclude this activity, take the class back to the cave entrance. Discuss food-chains within the cave, and how the cave's food-chain is connected with the one outside the cave. Discuss evidence of vandalism and students' feelings about it. (See questions at bottom of Geological Features handout.)



  1. Repeat lava-flow simulation now that its effects have been observed in the cave


  2. Study spelunking and plan a longer trip in which the class explores more of the cave's length


  3. Walk The Trail of Two Forests at the Lava Cast Picnic Area


  4. Read Ape Cave and the Mount St. Helens Apes, by William R. Halliday



Lava Falls Walk


Goal: To acquaint students with the unique geological features of the Mount St. Helens lahar.

Objectives: Students will

  1. Observe dramatic effects of the 1980 Mount St. Helens eruption
  2. Participate effectively in a cooperative group task
  3. Focus their attention on and identify selected features of this landscape
  4. Appreciate their own impact on natural features and landscapes

Concept: Dramatic geological events shape the earth in ways that may seem ordinary and indiscernible to the untrained eye. These events also leave behind extraordinary puzzles and anomalies. From some of those created by the recent eruption, we can learn much that is new about the nature and power of volcanic activity.

Summary: Students look for, identify and sketch six selected features of the lahar they will encounter on a 40-minute walk. They are encouraged to participate actively in small-group exploration and examination, and engage in creative interpretation, in order to fully experience the richness of this environment.

Content Areas: Science (geology), art

Materials Needed:


  1. Lava Falls Images
  2. pencils
  3. paper
  4. clipboards or notebooks

Teacher Narrative: A Lahar Tells a Story

Evaluation: Because the intent of this lesson is to encourage maximum engagement and creativity, and may serve to set the tone for other study activities on the lahar (see the Disturbance Ecology Lessons), formal grading is not recommended.

Instructional Sequence:

  1. Gather students in the parking lot as they leave the bus. Identify landmarks: Lava Canyon, the lahar, Mt. Adams, Hood, Rainer, the blast zone, Shoestring Glacier, etc. Give instructions for protecting this ecologically sensitive area. ("Take nothing but pictures; leave nothing but footprints!") Read aloud the narrative which follows.


  2. Introduce the Lava Falls Images activity handout. Reassure students that artistic talent is not required, and that sketches may be accompanied by descriptive narrative. Remind them to walk carefully and minimize disturbance to the environment. Each student will need to find one example of each item on the handout; however, no one is expected to do so without the assistance of others. They should confer, share ideas, point-out "discoveries" to each other, etc.


  3. Accompany the students and circulate among them, but tell them they are "on their own" in terms of finding answers. Their findings and conclusions, ideas and questions will be addressed in the follow-up discussion.


  4. Following the walk, reassemble the students to share their drawings and discuss their findings. For the benefit of those unable to identify the assigned features, retrace your steps, pointing-out and explaining all six.

Time and Time Again: A Stratigraphy Activity


Goal: To provide students with opportunity to observe the record of 13,000 years of Mount St. Helens history at a cliff on the lahar which reveals stratigraphic bands, and to impress upon them the immensity of geologic time.

Objectives: Students will demonstrate

  1. Understanding of the cyclic and varied nature of volcanic activity


  2. Understanding of the ways in which these varied forms of activity help to determine the surrounding topography


  3. Ability to differentiate and describe various layers of deposition


  4. Appreciation of the challenges faced by geologists in the tracing of natural history.

Key Concepts: Volcanic activity constructs topography. Volcanic eruptions have been varied in form, and will continue to occur in a variety of ways. The stratigraphic layers at Mount St. Helens help to reveal its history, and aid in predicting its future.

Summary: At the stratigraphic bands site, the teacher will lower from the top of a low cliff a series of signs, fastened at intervals to a rope, which are maintained in that location and mark the strata revealed there. Students observe, describe characteristics and record evidence of six of Mount St. Helens' eruptive periods. They identify specific traits of lahars, pyroclastic flows, and airfall found in stratigraphic depositions from these periods.

Content Areas: Earth Science, History

Materials Needed:


  1. Stratigraphic Bands Activity Worksheet
  2. Stratigraphic Bands Activity Key
  3. Summary of Geological History
  4. pencils
  5. paper
  6. clipboards or notebooks

See also Classroom Supplements folders.

Evaluation: Completed, corrected worksheet may be used to study for quiz or project on eruptive periods.

Instructional Sequence:

  1. Lower and arrange signs at the stratigraphic bands site, and explain to students that the signs identify layers corresponding to the six eruptive periods on their worksheets. Point out that the distance between knots on the rope is one foot. Note that the bands revealed here account for only the last 13,000 years of the 40,000 years of volcanic activity presently identified, and that inter-pretations of the evidence are, by nature, speculative.
  2. Explain how to complete the Stratigraphic Bands Activity worksheet, to include thickness, description of eruptive material, and artifacts of plant and animal life contained in the layers.
  3. Discuss the challenges of determining what each layer represents, the cyclic nature of Mount St. Helens eruptive activity, and the use of examination of past depositions to predict future eruptions.
  4. Ask questions to stimulate thinking, such as what root artifacts in the layers can tell us about former environments; what the layers reveal about how lakes in the area were formed, etc.
  5. Give the group ample time to complete and to discuss the questions at the bottom of the worksheet. It is imperative that the teacher move from group to group during this time to address concerns and answer questions. Have the group suggest mnemonic devices -- image associations, limericks, phrases, acronyms, etc. -- as aids to remembering the names of the periods in order.


Extension Activity:


  1. Correlate this activity with the "A Place in Time" activity and dates of volcanic eruptions with concurrent events in world history.




Disturbance Ecology

Instructional Strategies

Peer Editing and Writing as Process

Until the late 1960's and early 70's, teachers and consequently students were commonly taught about the tools of the craft of writing -- grammar, punctuation, spelling, usage, and handwriting -- but not about the craft itself.


In truth, however informal it may be, writers use a process that typically includes these stages: prewriting and planning, writing a first draft, responding and revising, editing and proofreading, and writing a final draft.


Looking Back to 1980 is one of several lessons in this curriculum which offer opportunity to use the peer-editing process.




In "Balance the Basics: Let Them Write," a 1980 Report to the Ford Foundation, Donald H. Graves offers the following arguments for the importance of writing as a learning tool.


  1. Writing contributes to intelligence by requiring analysis and synthesis of information.
  2. Writing develops initiative, by requiring that the student supply everything him/herself.
  3. Writing develops courage, by requiring that the student give up anonymity.
  4. Writing increases the student's personal knowledge and self- esteem.
  5. Writing encourages learning in all subject areas, by employing auditory, visual, and kinesthetic systems all at once.
  6. Writing contributes significantly to improvement in reading skills.
Advantages of group collaboration in the writing process include the reduction of writing anxiety, overcoming some of the difficulties students encounter in "getting started," emphasizing the importance of addressing a particular audience, focusing on "getting it right" through multiple revisions and drafts, and establishing a norm of critical self-evaluation.


The Stages:


Writing activities are an important feature of A Living Laboratory, with special attention given to small-group collaboration in the prewriting, responding and revising, editing and proofreading stages. Attention to the following steps may help you effectively use writing as a teaching tool, whatever your content specialty may be.
  1. Prewriting (Preparing to write)
    • Read, think, free-write in a journal format
    • Identify purpose and audience
    • Research, take notes, gather information
    • Brainstorm with a peer group (See Clustering/Mindmaping)
    • Organize thinking and plan


  2. Drafting (Putting thoughts on paper)
    • Focus on content (quantity and quality to be considered later)
    • Compose freely, without concern for mechanics


  3. Revising (Taking another look)
    • Maintain focus on content vs. mechanics
    • Share draft with peer group
    • Invite discussion, accept response and helpful input from peers
    • Add to, delete from, rearrange and revise first draft


  4. Editing/Proofreading
    • Share revised draft with peer group
    • Invite correction of grammar, spelling, punctuation, usage
    • Incorporate corrections in final draft


  5. Publication (The final draft)
    • Share the product with peer group (dramatizations, small group reports, individual oral presentations, etc.)
    • Invite evaluation by peer group
    • Submit for final evaluation by teacher


The Magic of Metaphor

Metaphor is used extensively in A Living Laboratory: Volcanoes to "stretch" students' thinking skills, to enhance the learning process by creating vivid imagery that establishes powerful connections between the concept and the student's prior learnings and personal experiences.


The use of metaphor as a teaching tool has a long history. As teachers, we use metaphor regularly (often unconsciously) to explain ideas, insights, and abstractions. Metaphorical thinking is the ability to make connections between two unlike things, by recognizing an inherent similarity or a common trait.


For example, in Teaching to the Two-Sided Mind, Linda Williams likens the right hemisphere of the brain to a kaleidoscope. This single image serves to illustrate the critical attributes of the right hemisphere; i.e., simultaneous, nonlinear processing that creates meaningful patterns out of unconnected bits and pieces of information.


Williams then compares the left-brain hemisphere to a digital computer, representing the linear and sequential processing skills identified with this portion of the brain.

Metaphor is an excellent technique for introducing unfamiliar material. It is a proven aid to retention and recall. Through the use of metaphor, students are able to connect new information with something they already know or have experienced, attaching it to existing "schema" in the mind.


The second essential step in this learning process is what Gordon and Poze, The Metaphorical Way of Knowing, call "making the familiar strange." This is where students break known connections in order to discover something new about what was previously learned. "Breaking connections" to form new metaphors is an effective way to move from recall to the higher-order levels of cognitive activity: synthesis, integration, and evaluation of the learning.


Metaphors also may be used to evaluate students' ability to comprehend, apply, analyze, synthesize, and evaluate. Williams suggests using metaphors in test questions. She offers as an illustration this question used to evaluate students' understanding of the French Revolution: "How was the period leading up to the French Revolution like the building up of a thunderstorm? Be sure to include in your analogy the major events that led to the revolution." Following a question posed in terms of a metaphor, students are asked here to demonstrate their understanding of a concept by creating metaphors of their own.


When planning a lesson around a metaphor, the following steps are necessary:


  1. Decide what is the general principal or concept underlying what you are teaching.


  2. Brainstorm possible metaphors, and select the one which best communicates the concept. Make sure the metaphor is one to which your students can relate.


  3. Once you have identified the metaphor, consider its possible discrepancies (the ways in which it does not fit the concept), so that you can note and/or clarify those discrepancies as you introduce it to your students.


  4. Introduce the new lesson or information using the metaphor you have selected. At the conclusion of the lesson/activity/unit, allow time for students to generate new, original metaphors that also communicate the concept learned.

The lessons Vulcan's Vocabulary and A Place in Time illustrate the use of metaphor.


Another way to use metaphor in the classroom is to approach it integratively or thematically. The following steps are suggested by Donald and Judith Sanders in Learning, February 1987:


  1. Establish a specific objective for the lesson and the broad concept to which you will relate it.


  2. Choose an appropriate metaphor that illustrates the concept.


  3. Write a guided fantasy or plan an activity that actively involves your students with the metaphorical image.


  4. Introduce the lesson using the metaphor you have chosen.


  5. Read your guided fantasy or engage students in the activity that allows them to "experience" the metaphor in their imaginations.


  6. Ask students questions about the experience (What did it feel like? What did it look like? What feelings did you have? What new ideas/realizations occurred to you?)


  7. Tie the metaphorical image to your original lesson goal, such that students "get the connection": the "A-HA!" moment of creative recognition or insight.


Guided fantasy or imagery techniques promote both visualization and relaxation, encouraging students to open "the mind's eye" to an experience as it is described to them. It is a means of integrating the rational with the creative mind, freeing the listener from some of the emotional barriers to learning. It has been shown to be particularly effective in cases of undue stress, a history of repeated failure, compulsive perfectionism, and other sources of blocking and anxiety. It is even credited by some with inhibiting acting-out behaviors and increasing motivation. 


Like other forms of imagery, guided fantasy helps to make the abstract familiar, and aids learning and retention by establishing memorable mental connections. (For an example of this method, see lesson Evacuation Simulation. This lesson to be on line in the future.)


Memory Aids


Learners must often remember unfamiliar words and lists of words that are not related to their daily lives. Some "tricks" can be used to aid our memory. These are called mnemonic devices. If you aren't already using them, try some of the mnemonic devices below to help you remember vocabulary and lists in A Living Laboratory: Volcanoes.


  1. Give it a name: "Caldera Rivera," "Basalt Rathbone," Ashley Ashfall," etc.


  2. Use a simile: "A caldera is like a witches cauldron." "Basalt flows like ice cream from a volcanic cone." "It looks like . . . . . .," "It sounds like . . . . . ," etc.


  3. Use a metaphor that creates a mental picture: "The witch, Caldera Rivera, stirs a bubbling cauldron of magma."


  4. Draw a picture to represent it.


  5. Pair it with a familiar word that rhymes: "You can't throw a discus that's viscous"


  6. Create a nonsense acronym:


"The debris avalanche at Mount St. Helens was composed of SWIRT."

Cooperative Learning

    We destroy the love of learning in children, which is so strong when they are small, by encouraging and compelling them to work for petty rewards--gold stars, or papers marked 100 and tacked to the wall, or A's on report cards, or honor rolls, or dean's lists or Phi Beta Kappa keys--in short, for the ignoble satisfaction of feeling that they are better than someone else.

    --John Holt


Learning can be structured competitively, so that students work against each other; individually, so that students work alone; or cooperatively, so that students work together to accomplish shared learning goals. David W. and Roger R. Johnson, professors, and co-directors of the Cooperative Learning Center at the University of Minnesota, recommend that, while all three structures should be used, cooperation should play the dominant role in any classroom.


Why? Over 122 studies conducted between 1924 and 1981 provide clear evidence that cooperative learning experiences promote higher achievement than their competitive or individualistic counterparts. Cooperative activities also tend to promote the development of higher-order levels of thinking, essential communication skills, improved motivation, positive self-esteem, social awareness, and tolerance for individual differences.



Specifically, recent research links regular cooperative experience in the classroom with gains in the following areas:



  • Student achievement
  • Critical and creative thinking
  • Positive attitudes toward subject and school
  • Group interaction and social skills
  • Self-esteem and mutual respect


In order for cooperative activities to be successful, teachers need to give attention to the following key elements:


    1. Teamwork
    2. Support, and acceptance of differences
    3. Active/reflective listening
    4. Positive feedback
    5. Reaching consensus
    6. Coaching and tutoring others
  2. A. Group Size/Composition -- Johnson and Johnson report the highest levels of success occur when groups are kept small. In fact, they favor groups of two (dyads) for many cooperative tasks, with the number of group members increasing in proportion to the complexity of the task. Teachers introducing cooperative learning for the first time might let students select their own groups. But once comfort is established, the greatest potential for benefit occurs in heterogeneous groupings, with the teacher assuring a balanced mix of ethnic groups, females/males, handicapped with non-handicapped students, and students of low-to-high ability and productivity.

    B. Group Functions -- Students may work in groups on any of the assignments they would ordinarily do alone. They may meet to collaborate on solving a problem, to discuss an issue without direct leading by the teacher, to brainstorm for new ideas or summarize what they have learned about ideas previously presented, to formulate concepts out of information and facts they have been given. Particularly valuable is the potential of a group to share the parts of a complex project or jointly produce an assigned product. Goals for the group might range from practice in group communication processes to preparation for a presentation to the whole class group.

    C. Group Norms -- Teachers need to proceed slowly and with patience to introduce students to cooperative learning. It is not enough to rearrange the seating. A "culture" of group work needs to be developed that includes expectations regarding noise level, an atmosphere of trust, absence of "put-downs," equal participation, and willingness to help one another. The use of group grades is controversial, but Johnson and Johnson report good results from encouraging "we sink or swim together" mindsets. It is important that students learn to coach and teach each other. Brighter students' learning is enhanced by their efforts to teach the others; less-capable students benefit from increased one-to-one attention.

    D. Group Skills -- Students need to be taught procedures and given practice opportunities for rearranging the classroom space, moving quietly into groups, responding to teachers' signals for attention, etc. So, too, it is important for them to receive explicit instruction and regular practice in the interpersonal skills that this method, as well as life in a democratic society, requires. These include:


    E. Group Goals and Roles -- Clear instructions, goals, and time lines for group activities are essential to successful cooperative learning. It is also important that each member have a specific function within the group: recorder, reporter, monitor, observer, facilitator, etc. Roles should be changed frequently, so that members have opportunity to practice new roles, and should be designed to fit the group's particular task.


Activities in A Living Laboratory: Volcanoes may be used to introduce your students to cooperative learning, or fit well into an existing cooperative program.


One such activity is "Jigsaw" (Aronson, 1978) a cooperative learning process for students from kindergarten through graduate school. Students are assigned to small heterogeneous teams, and the task to be learned and materials are divided into as many sections as there are members on each team. For example, a biography might be broken into "early years," "schooling," "first accomplishments," and so on. A study of plants might be divided into "food sources," "chemical manufacturing," etc. A study of a country might be segmented into geography, culture, industry, transportation, and government.


First, members of the different teams who have the same section form "expert" groups and study together. Each then returns to his or her team and teaches that section to his or her teammates. Jigsaw requires that students depend on and learn from one another. (See among other lessons Eruption Simulation, and Life on a Fiery Planet for adaptations of this technique. These lessons to be on line in the future.)

Cooperative Learning References


Aaronson, E., The Jigsaw Classroom (Beverly Hills, CA: Sage Publications, 1978)

Devries, D. L., "Teams-Games-Tournaments: Review of Ten Classroom Experiences," Journal of Research and Development in Education 12:28-38, 1978

Dishon, D. and O'Leary, P.W., A Guidebook for Cooperative Learning (Portage, MI: Cooperation Unlimited, 1984)

Johnson, D. W. et. al., Circles of Learning (Washington, D.C., ASCD, 1985)

Kagan, S., Cooperative Learning: Resources for Teachers (Riverside, CA: University of California, 1985)

Kohn, A., "It's Hard to Get Left Out of a Pair," Psychology Today, October, 1987 (on work of Johnson and Johnson)

McKisson, M. and Wasley, P., "China Connections: A Computer Simulation Game," 1987

Sharan, S., and Sharan, Y., Small-Group Teaching (Englewood Cliffs, NJ: Educational Technology Publications, 1976)

Slavin, R. E., "Learning Together: Cooperative Groups and Peer Tutoring Produce Significant Academic Gains," American Educator, Summer 1986, pp. 6-13

Slavin, R. E., "Student Teams and Achievement Divisions (STAD,) Journal of Research and Development in Education 12:39-49, 1978

Slavin, R. E. Using Student Team Learning (Baltimore, MD: Johns Hopkins Learning Project, 1980)

Clustering/Mindmapping Techniques

Highly visual or tactile-kinesthetic learners typically have difficulty with lectures, and may avoid them altogether. Such avoidance or aversive behavior can create deficits that seriously hamper learning in traditional educational settings.


These learners can be assisted to make good use of the lecture method. They may be taught to apply to their note-taking the techniques of "clustering," developed by Gabriel Rico, and mind-mapping, created by Tony Buzan. Like brain-storming and often used with it, these techniques employ free-association of ideas, creating a "structure" quite unlike the traditional outline method, but equally effective. They represent one way that visual and tactile-kinesthetic learners may adapt their learning needs to fit the given situation.


These strategies are useful not only for organizing information, but for generating ideas. They are used to create patterns, build connections, and establish associations between the student's own experience and new information, between known facts and new concepts, between parts of a concept or problem and its whole.


Random, non-sequential, and non-linear methods like these are ideal for the visual, tactile-kinesthetic, Type 1 and Type 4 learners. Furthermore, by utilizing skills inherent to both sides of the brain, they become very valuable techniques for the more sequential learner to employ. Finally, they are compatible with "schema" theories of cognitive processing advanced by Costa, Ausubel, Neisser and others.


In both techniques, the learner begins with a center or nucleus. The general idea of the lecture, book, or movie, the topic for creative writing, or the central issue in a problem-solving exercise, is placed in the center of the page. Main ideas are connected to the central topic by drawing lines from the center. Supporting ideas become "branches" off main ideas. Working outward from the center in all directions, the learner produces a growing, organized structure composed of key words, phrases, and images.


Mindmaps are useful for chapter reviews, test preparation, planning, organizing, report-writing, note-taking, and generating ideas for creative writing or research. They are an invaluable technique for introducing a new lesson geared to Quadrant 1 of the 4MAT cycle (See also Learning Styles and the 4MAT System.)


In this curriculum, for example, students being introduced to study of Mount St. Helens are asked to mind-map everything they already know about the volcano. (See Eruption Simulation.) The map becomes a graphic representation of the knowledge level of the students, allowing the teacher to easily identify the gaps in their information. From this visual display, students can draw conclusions and pose questions for further exploration. The process serves as both a motivational technique and as a way of establishing the students' baseline knowledge. Instruction can be modified and adapted, made more basic or more elaborate, based on this information about students' level of readiness.


In A LIVING LABORATORY: VOLCANOES, mindmaps are also used to review information or synthesize new learning. It is helpful and enjoyable to create color mindmaps. We tend to remember better when ideas are presented in color, and the use of colored chalk to highlight main ideas in a lecture has been shown to enhance learning.




Finally, clustering is an especially effective tool for the prewriting stage of the writing process (See Peer Editing.) The following, excerpted and adapted from Writing the Natural Way by Gabriele Rico, may help you introduce clustering to students.


What is it?

Clustering is a generative, open-ended, non-linear, visual structuring of ideas, events, feelings. It is a way of mapping an interior landscape as it begins to emerge.


What is it based on?

It is based on a beginning knowledge of how the two sides of our brain process what we know. They process information in radically different ways. This difference is most easily explained by a look at two words often thought to be a synonymous: order and structure.


Order, on the one hand, comes from the Latin ordo, ordini. It means "in a straight row," "in a regular series." Order implies linear, rule-governed activity. Order is imposed from without. Structure, on the other hand, comes from the Latin struere. It means "to heap together." Structure emerges from within.


What will clustering do?

  • Clustering should help you find and generate ideas and, having found them, to structure and restructure them long before any ordering actually takes place.
  • Clustering is a technique for collecting thoughts around some stimulus, for finding a focus, and for allowing a sense of the whole configuration to emerge even though all the details are not yet apparent.
  • Clustering is a technique for engaging and utilizing the raw materials of one's experience and giving them a tentative shape. In short, it is a discovery process.


How does clustering work?

For brief journal entries, clustering is a simple process taking thirty seconds to two minutes, just long enough to let ideas spill out onto a page until an idea presents itself that you can develop into a whole.



Buzan, Tony, Use Both Sides of Your Brain (New York: Dutton, 1974.) Costa, Arthur, Developing Minds (ASCD, 1985)

Rico, Gabriele, Writing the Natural Way (Los Angeles: J. P. Tarcher, Inc., 1983.)

Classroom Supplements

Eruptive Periods in Context (*1)

Approximate Dates Stages/periods
Approx. Age in Years Before 1980
Volcanic Activity/Effect
Historical Event(s)
1980- Most recent eruption
Laterally directed blast from cryptodome followed by eruption of dacite tephra and pyroclastic flows. Heat unleashed during the eruption melted glacial snow and ice. The melt water combined with rock and mud to form a liquid sandpaper-like mixture called a lahar. Shattered stumps remain, testifying to the abrasive force of the lahar. The flow surged up a 120-foot high section of hill, scouring away the forest in its path. The lahar raced down the Muddy Tiver and Pine Creek drainages into Swift reservoir. A dome developed in a new crater. Man on the moon (1970)

Alaska granted statehood (1959)

WWll (1941)

WWl (1919)


1776-1857 Dormant interval of 123 years.

Goat Rocks eruptive period.

180-123 (*2) Eruptions of daicite, tephra, andesite lava flow, dacite dome.

X Tephra layer: fiery red arteries of andesitic lava pulsed down the southeast side of the volcano. These lava flows can be seen from the lahar viewpiont and are called the worm flows. Pasty, sticky dacite lava oozed out of the volcano, crowning the pre-1980 summit with a lava dome.

Declaration of Independance (1776)
1480-1650 Dormant interval of about 200 years

Kalama (*3) eruptive period

350-500 (*4) Eruptions of daicite, andesite tephra, dacite dome(s) and pyroclastic flows, andesite lava flows.

We Tephra layer: Scorching hot pyroclastic flows tumbled down the volcano. Winds blew mushroom shaped ask plumes to the east. The Kalama, with Goat Rocks and Sugar Bowl periods, built the symmetrical cone shape of Mount St. Helens. Most rocks visible on the surface originated during the Kalama.

Columbus sets sail (1492)
800 Dormant interval of about 650 years

Sugar Bowleruptive period

1150 Eruption of dacite dome. laterally directed blast, pyroclastic flow(s), air-fall tephra.

Wn Tephra Layer: Swirling plumes of ash rushed skyward. Prevailing winds deposited tephra in southeast British Columbia.

Viking explorations
300 BC-250 AD Dormant internal of about 600 years

Castle Creekeruptive period

1700-2200 Eruptions of andesite, dacite, and basalt tephra, andesite and basalt flows, andesite and dacite pyroclastic flows.A variety of material was ejected from the volcano, marking a significant change in the eruptive behavior of Mount St. Helens. These constructive eruptions built most of the modern volcano. Prior to this time, dacitic lava had been the primary lava type. During this period, pasty dacite lava was accompanied by fluid basaltic lava, and andesitic lava (lava with properties between basalt and dacite).

Bh Tehpra Layer: fluid red ribbons of basaltic lava spilled down the volcano and formed Ape Cave.

Bo Tephra Layer: Dacitic pyroclastic flows and rivers of basaltic lava surged down the slopes of the volcano.

Bi Tephra layer: Andesitic lava and pyroclastic flows spilled down the volcano.

Bu Tephra layer: Glowing rivers of basaltic lava flowed from the volcano.

Roman Empire in power

Christ lives

1200 BC-700 BC Apparent dormant internal of about 300 years

Pine Creekeruptive period

3000-2500 Eruptions of dacite tephra, dacite domes, pyroclastic flows. Mount St. Helens awoke from a brief slumber with a series of small explosive eruptions. Searing hot pyroclastic flows tumbled down all sides of the volcano. Airfall tephra from these eruptions lift four distinctive deposits on Mount Rainier!

Tremendous lahars scoured down the volcano into the Lewis and Toutle river valleys. Spirit Lake over topped the natural dam created during the Smith Creek period and formed a huge mudflow that roared down the North Fork of the Toutle River Valle. This mudflow blocked a stream tributary (similar to the formation of spirit Lake) and formed Silver Lake.

Greek civilization begins


2600 BC-1600 BC Apparent dormant internal of about 300 years


Smith Creekeruptive period

4000-3300 Eruptions of dacite, tephra, dacite domes, pyroclastic flows; probably included dormant intervals as long as several centuries. Billowing clouds of tephra rocketed towards the sky during what was likely the largest eruption in the hitory of the volcano. Nearly 2.5 cubic miles of tephra was ejected from the volcano, in contrast to 0.1 cubic miles deposited during the May 18, 1980 eruption.

Yn Tephra layer: Pumice from this eruption has been found in Canada up to 500 miles away from the volcano.

Ye Tephra Layer: Intense heat from the erupting volcano melted snow and Ice. The melt water mixed with rock and mud, forming cement-like slurries called lahars. A lahar plugged the North Fork of the Toutle river, blocking a stream drainage. Spirt Lake formed behind this natural dam. 

Egypt builds pyramids


12000 BC-9000 BC Apparent dormant internal of about 5000 years(?)

Swift Creekeruptive stage

13000-10000 Eruptions of dacite tephra, dacite domes, litihic and pumiceous pyroclastic flows; probably included dormant intervals of at least a few centuries. Repeated powerful explosions hurled ash and pumice into the air. Many superheated rock avalanches called pyroclastic flows raced down the slopes of the volcano.

S Tephra layer: large eruptions of pumice and ash called tephra were blasted into the air. Tephra from this eruption was found in central Washington!

J Tephra Layer: Winds blew towering clouds of tephra to the west. This was the only time that pumice was deposited to the west in any significant amount. 

First migrations across Bering land bridge into North America.


19000 BC-16000 BC Apparent dormant internal of about 5000 years(?)

Cougareruptive stage

21000-18000(?) Eruptions of pumice tephra, one or more dacite domes and lava flows, lithic and pumiceous pyroclastic flows; probably included dormant intervals of at least several centuries. Crater Lake is formed.


Apparent dormant internal of about 15000 years(?)

Ape Canyon eruptive stage

50000-36000(?) Eruptions of tephra and pumiceous pyroclastic flows.

(*1) - Derived from Crandell, Dwight R., Deposits of pre-1980 Pyroclastic Flows and Lahars from Mount St. Helens Volcano, Washington (USGS Professional Paper 1444: U.S. Fovernment Printing Office, Washington D.C., 1987)

(*2) - Years before 1980, based on tree-ring dates and historic records

(*3) - Boldface periods/stages visible at stratigraphic bands study site

(*4) - Years before 1980, based on tree-ring dates and 14-C dates

Mount St. Helens Eruptive Activity, 1980-1984

The Two-Month Precursory Period


The Mount St. Helens volcano reawakened in March 1980 after more than a century of quiet. A magnitude 4.0 earthquake on March 20 was followed by two months of intense earthquake activity, and phreatic "steam-blast" eruptions which began on March 27. Ejecta from these phreatic eruptions were composed of fragments of pre-existing rocks; no magma was tapped during these eruptions. These events were caused by the intrusion of viscous magma into the volcano, shoving the north flank outward more than 300 feet and creating the famous `bulge.' Repeated surveys during April and May showed that the bulge was growing northward at an average rate of about five feet per day.


The Eruption

A magnitude 5.1 earthquake on May 18 (8:32 a.m. PDT) shook loose the steepened bulge on the volcano's north flank, resulting in the largest known landslide in historic time, 2.3 cubic km (0.56 cubic miles). The entire north flank was described by an aerial observal as "rippling" and "churning" moments before "the north side of the summit began sliding north along a deep-seated slide plane."

As the avalanche reached the north base of the cone, the topography it encountered caused it to be divided into three sections:


Part of the avalanche slid into Spirit Lake, raising the lake bed roughly 180 feet, and damming its natural outlet. Water displaced by the avalanche surged up the surrounding hillslopes, washing the blown-down timber from the lateral blast into the lake.


Part of the avalanche "ramped" up and over a 1,200 foot high ridge five miles north of the volcano (Johnston Ridge) depositing debris on top of the ridge and in the South Colwater Creek drainage.


The bulk of the avalanche was deflected westward down the North Fork of the Toutle River valley. The front of the avalanche traveled a distance of 15 miles in about 10 minutes. The resulting deposit covers the valley floor to an average depth of 150 feet, but it is more than 500 feet deep in a few places (such as 1.5 miles west of Harry Truman's Lodge).

The hummocky avalanche deposit covers a total area of about 24 square miles. It consists of intermixed volcanic debris of various sizes, including blocks, pebbles, sand and silt, and blocks of glacial ice.

Lateral Blast

The sudden removal of the volcano's north flank released pressure on the hydrothermal and magmatic system within the volcano, triggering a devastating lateral blast to the north. The abrupt pressure release, or "uncorking," of the volcano by the avalanche can be compared in some ways to the removal of the cap from a vigorously shaken bottle of soda pop, or to punching a hole in a boiler tank under high pressure.

The northward-directed lateral blast of rock, ash, and hot gas devastated an area of about 150 square miles. The blast stripped trees from most hill slopes within six miles north of the volcano and leveled nearly all vegetation for as far as 13 miles in a 180-degree arc north of the mountain. The blast deposited blocks and smaller rock fragments and organic debris over the devastated area in layers to more than three feet in thickness. Surrounding this zone of toppled vegetation is a narrow band of scorched but standing timber in which sandy deposits are as thick as four inches; this zone has an area of about 25 square miles.

Plinian Column (Vertical Eruption)

A vertically-directed ash column erupted from the newly formed horseshoe-shaped crater within minutes of the lateral blast. Within ten minutes, the ash column reached an altitude of more than 12 miles. Ash from this eruption cloud was rapidly blown east-northeastward by the prevailing winds, producing lightning and starting hundreds of small forest fires, and causing darkness eastward for more than 125 miles. Ash fell visibly over the Great Plains, and fine ash was detected by systems used to monitor air pollution in several cities of the northeastern United States. Some ash drifted around the globe within about two weeks. The eruption subsided by late afternoon on May 18; by early May 19 the eruption had stopped.

The air-fall ash deposited during the nine hours of vigorous eruptive activity amounted to about 540 million tons distributed over an area of more than 22,000 square miles. The volume of uncompacted ash is equal to about 0.05 cubic mile of solid rock, or only about ten percent of the amount of material that slid off the volcano during the avalanche.

Lahars (Mudflows)

Lahar is an Indonesian term used to describe dense, viscous flows of volcanic debris and water resembling wet concrete that form during a volcanic eruption or originate on the slopes of a volcano. These mixtures typically contain 60 percent sediment and 40 percent water by volume. Lahars occurred on nearly all streams draining the volcano during the eruption and were formed in three major ways:


Within minutes of the eruption's onset, hot pyroclastic surges mixed with snow and ice on the upper flanks of the cone, forming major lahars in the South Fork Toutle River, Pine Creek, and Muddy River drainages. Subsequent calculations indicate the surges, which are air-mobilized, low density, turbulent clouds of volcanic debris, were moving initially up to 120 ft./sec. (80 mph), but slowed considerably as they transformed into denser, water-mobilized lahars on the lower slopes of the volcano. The Pine Creek lahar reached Swift reservoir by about 9 a.m.; the Muddy River lahar arrived at about 9:40 a.m.


The largest lahar originated in the slumping and flowing of water saturated parts of the debris avalanche deposit during the afternoon. This lahar peaked near the mouth of the Toutle River at midnight, flowing at velocities between 25 and 40 feet per second, and left deposits three feet thick on parts of the flood plain, and 15 feet thick in the channel. The mudflow in the Toutle River drainage area deposited more than 65 million cubic yards of sediment along the lower Cowlitz and Columbia rivers. The water-carrying capacity of the Cowlitz River was reduced by 85 percent, and the depth of the Columbia River navigational channel was decreased from 39 feet to less than 13 feet, causing disruption of river traffic and temporarily choking off ocean shipping.


The smallest lahars formed from the erosion and turbulent mixing of snow and ice by small, hot pyroclastic flows on the afternoon of May 18, and from small landslides of water-saturated tephra that liquefied.


Pyroclastic Flows

The term "pyroclastic" -- derived from the Greek words "pyro" (fire) and "klastos" (broken) -- describes materials formed by the fragmentation of magma and rock by explosive volcanic activity. Pyroclastic flows are composed of hot gas, entrapped air, and different-size particles of fragmented magma and old volcanic rock (ash, blocks, bombs). Pyroclastic flows travel at great speeds in response to gravity (up to 60 to 100 miles per hour).

Pyroclastic flows were first directly observed at 12:17 p.m. and continued intermittently during the next five hours of strong eruptive activity. Smaller pyroclastic flows were erupted during the first few minutes of the avalanche lateral blast sequence. The successive outpourings of pyroclastic material consisted mainly of pumice and ash derived from new magma. Fragments of preexisting rocks were minor components.

The pyroclastic flow deposits formed a fan-like pattern of overlapping sheets, tongues, and lobes that extend five miles north of the crater. Temperature measurements made in these pyroclastic flows were still 780 degrees Fahrenheit two weeks after the eruption. Many "rootless" steam-blast explosions formed small craters on the northern margin of the deposits near Spirit Lake, as encroaching ground water was flashed into steam by the hot material. These steam-blast explosions continued intermittently for several weeks or months after the emplacement of the pyroclastic flows.


Explosive Eruptions

Following May 18, Mount St. Helens erupted explosively five times during 1980. None of these eruptions was as large as the events on May 18, but each eruption produced ash columns 25,000-50,000 feet above sea level and hot, dry pyroclastic flows of pumice and ash that swept down the north flank as fast as 60 miles per hour. These pyroclastic flows deposited ash and pumice fragments in fan-like patterns of sheets, tongues, and lobes in an area extending up to five miles north of the vent. Individual pyroclastic-flow units were generally less than 15 feet thick, and maximum temperatures recorded several hours after their deposition ranged from about 570 to 1,350 degrees Fahrenheit. The thickness of air-fall deposits ranged from one-third to one-fortieth that of the May 18th air-fall deposit at a given distance from the volcano.

Lava extruded from the vent and formed lava domes within a few days after the June 12, August 7, and mid-October explosive eruptions. The June and August domes were blown away by subsequent explosive eruptions, but the October dome survived to form the core of the present dome.

Domes are formed by thick, pasty masses of lava too sticky to flow very far from the vent. Lava of the Mount St. Helens dome is dacite. It contains a higher percentage of silica than the Hawaiian basalts and is about one million times more viscous.

Dome-building Eruptions

Eleven eruptions after October 1980 were dominantly nonexplosive events that built a composite lava dome about 800 feet high and 2500 feet in diameter in the crater. Each eruption extruded near the top of the dome and crept three to 15 feet per hour down one side over a period of several days; between 100 and 150 million cubic feet of new lava was added to the dome during each of these episodes.

Dome-building eruptions in 1981-82 were episodic, occurring every one to five months. Between February 1983 and February 1984, the dome grew continuously both by the intrusion of magma into it and by the extrusion of lava onto its surface. As of May 1984, it appeared that Mount St. Helens had returned to the episodic style of dome growth. At the then current rate of dome growth, which averaged about 35 million cubic feet per month, it was estimated that some 150 to 200 years would be needed to build Mount St. Helens to its former height. However it was considered unlikely that such a simple scenario would prevail.

Small Explosions

Small explosions sometimes precede or accompany the dome-building eruptions at Mount St. Helens. If they occur when snow mantles the crater floor, they can produce mudflows and snow avalanches. The explosive onset of the March 19, 1982, eruption hurled hot pumice and dome rocks against the 2,000-feet-high south crater wall, dislodging snow and rock that avalanched through the crater and down the north flank of the volcano. Deep snow in the crater melted quickly from the volcanic heat, forming a temporary small lake from which a destructive flood swept down the north flank and into the North Fork Toutle River. About a day later a new lava lobe began to flow down the southeast flank of the dome.

Tephra Emissions

In addition to the dome-building eruptions, vigorous emissions of gas and tephra have occurred from fractures and small craters on top of the dome since late 1980. These periodic outbursts usually last several minutes, occasionally sending ash plumes as high as 15,000 to 20,000 feet above the volcano. Most of the tephra consists of fragmented pieces of dome rock, not new liquid magma, in contrast to the more hazardous magmatic explosions of 1980. These events are intermittent, sometimes occurring several times per day, and at other times not occurring at all for several weeks.




Mount St. Helens Revisited #1

Food and shelter are still not abundant, and the volcano continues to rumble, but many kinds of animals -- both survivors of the eruption and recent immigrants -- are making efforts to repopulate the mountain.


by James A. MacMahon


Reprinted from Natural History, Vol. 91 (May 1982)


For many years to come and certainly long after the second anniversary of its May 18, 1980, eruption, Mount St. Helens will continue to provide scientists with an incomparable opportunity to observe natural repair processes at work. Yet the task of deciphering the story of life on the volcano has turned out to be more difficult than many scientists ever envisioned. Instead of an affected area of about 160 square miles that could be subdivided into three or four neat devastation categories, researchers have found that nearly every patch of ground must be sleuthed to reconstruct the causes of its fate since the eruption. Was the site forested, clear-cut or above timberline before the big event? Was it snow covered on the morning of the May 18 eruption? Did it receive only a shower of pumaceous material or was it subjected to the full fury of the mixture of hot gas and rock material known as pyroclastics?


Adding to the difficulties of reconstructing the past are the problems of predicting the future. It is impossible to tell what the future activity of the volcano will be, and a sizable eruption would probably destroy many of the present scientific study sites. Even as we go to press, the mountain is rumbling, and scientists disagree as to whether the volcano's dome is about to erupt or whether Mount St. Helens is in for a period of intensive dome building. One thing is sure, however. If the volcano erupts now or at some future time, plants and animals -- and scientists -- will undoubtedly return to the mountain and start their work again. Certainly all three groups have been busy since the mountain blew two years ago.


Survival of plant and animal life in the areas devastated by the May 18 blast was often due to a chance set of circumstances, which no one could have modeled mathematically and which were independent of the myriad adaptations organisms possess as a result of thousands of generations of evolution. A few hundred feet above Spirit Lake, for example, the presence of a single rock outcrop in the middle of the most ravaged lands seems to have permitted the survival, virtually unchanged, of an oasis containing the normal mix of plants and animals. The isolation of these islands of survivors may lead to genetic differences between populations derived from the survivors and more widespread populations of the same species. Such areas might also form a source from which organisms can recolonize the landscape faster than if recolonization occurred only from the perimeter of the large devastated area.


Being alive on May 19, 1980, however, was no guarantee of continued survival. Today, two types of organisms occupy the affected areas of Mount St. Helens: survivors (or their offspring) and colonizers. Those that lived through the original catastrophe may have been protected by the deep snow that was still present on some sites, or they may have been dormant in belowground burrows or safely ensconced at the bottom of a montane lake. Continued survival depended on the nature of the changes in their environment and their ability to cope with those changes. Many of the animals seen on the earliest reconnaissance missions in the summer of 1980 were not present in the spring of 1981. Some of those that have persisted have gone on to recolonize other parts of the volcano. Colonizers have also come from outside the regions affected by the eruption.


Because chance may spare a site within a devastated area and because survivors at one site may be colonizers in another, neither the types of organisms nor the categories of devastation are completely clear. Nevertheless, these categories and types can help clarify what happened during -- and since -- the eruption.


As Mount St. Helens erupted, its north slope broke up. Great chunks of the mountain and glacial ice flowed northward and westward in landslides and a debris flow that eventually turned into mud flows. A major tongue of this flow was directed into Spirit Lake, causing it to slosh up the side of its basin and scour the hills down to the bedrock in some areas. A more westerly directed arm followed the valley up the North Fork of the Toutle River. This landform contains blocks of material standing more than 90 feet above the surrounding area. The flow, as thick as 300 feet in some areas, averages more than 120 feet thick over a total area of about 23 square miles. Apparently no organisms were able to survive the mechanical damage caused by an overburden of this magnitude.


Damage caused by the blast itself depended on the distance from the volcano. The affected areas are characterized, in a very general sense, as the blast, or near, zone where trees were completely removed; the blowdown, or intermediate, zone where trees were leveled; and a scorch, or outer, zone where trees still stand but were scorched. Close to the volcano, many areas were also subjected to the high temperatures of pyroclastic flows and surges (hot mixtures of gases, ash, and up to boulder-size pumice and rock). Temperatures beneath the surface of materials deposited by these flows often exceeded 480 degrees F -- precluding the survival of organisms and creating some of the most desolate vistas on the volcano.


The volcano also deposited ash and other airborne materials. Beyond the scorch zone this is the only effect of the eruption. In such areas, including places on the relatively unaffected south slope of the volcano itself, the list of plant and animal species remains nearly the same as during preeruption times, although each species is often represented by fewer individuals. For example, at Butte Camp, on the south slope, Roger del Moral, Larry Bliss, and others at the University of Washington have compiled a plant species list that is virtually identical to a typical list for alpine areas in that section of the Cascade Range. Notable animals at Butte Camp are a black bear that has persisted in the area since the time of the blast and pocket gophers that have reproduced within the last twelve months.


This is not to say that the ashfall had This is not to say that the ashfall had no consequences: John Edwards and Lawrence Schwartz of the University of Washington have demonstrated in the laboratory that ash, by causing physical scarification of insect cuticle and subsequent desiccation, can kill individuals much as some commercial silica-dust insecticides do. Ash certainly killed many insects, but after the eruption, numerous sites in the high-ashfall zones close to the blast area contained up to seven species of ants, a dozen spider species, and more than fifteen beetle species, all survivors. At one of the oases above Spirit Lake, where ash is more than six inches deep, I have seen ground-dwelling spiders, two millipede species, a centipede, three ant species, and several beetles.


(Bees, whose dense body hairs act as a trap for dust, were among the insects hardest hit by the abrasive ash. Populations of these beneficial insects, however, are recovering. Ladybird beetles probably did not survive the May 1980 eruption, but ladybugs were back on the mountain as early as the summer of 1980. Aphids, feeding on surviving fireweed, provided the beetles with food.)


Evidence for the effect of ash on vertebrates is also somewhat debatable. As far from the volcano as eastern Washington, David Pyke of Washington Sate University has found deer mice (Peromyscus maniculatus) with signs of eye swelling that may have been induced by ash. In contrast, Doug Andersen of Purdue University -- my collaborator on Mount St. Helens -- and I have found no eye swelling in deer mice from our Spirit Lake blast site or from any of our high-ashfall areas fifteen to twenty miles northeast of the crater. Furthermore, we found no lung damage in any of the dead animals we examined microscopically. Interestingly, in 1945, less than four inches of ash near Iliamna Lake, Alaska, reportedly led to the death of certain rodents, blindness in rabbits, and illness in reindeer.


Richard Mack of Washington State University has documented ashfall effects on vascular plants in Washington and Idaho more than ninety miles from Mount St. Helens. Ash deposits mechanically overloaded several species, killing some and burying the fruits and flowers of others. The ash may also have dusted the leaves of some plants in ways that altered the energy balance, causing the leaves to overheat and die. Mack believes that the most important effects of the ash may become more obvious in the future if compacted ash alters the nature of seed residence sites and the availability of seeds to seed predators.


The kind of disturbance experienced by an area influenced not only what survived but also what can now successfully colonize the site. Potential colonizers, however, must first get there. The animals and plants that have moved into affected areas of Mount St. Helens, whether from oases on the volcano or from outside, must have good dispersal mechanisms. The cysts and spores of myriad microorganisms, carried along by winds, fall on the volcano constantly. Some plant seeds and spiders are also passively dispersed by winds. Immature spiders of many species spin threads of silk that remain attached to their spinnerets. These parachutelike apparatuses carry the spiderlings "on gossamer wings" and are responsible for the presence of young orb-web weaving spiders on the debris flow, an area that still supports very little life. Highly mobile animals, such as birds and some large mammals, were able to move easily into many devastated areas within hours or days after the eruption.


For all these migrants, getting on the volcano is just the beginning of their problems. For most species, suitable home sites and food sources are not available. Wood-boring insects would appear to be an exception. The abundance of downed timber led to some anticipation of a boom of bark beetles (Dendroctonus sp.) and an infestation of nearby valuable timberlands, but to date this has not occurred.


Not surprisingly, colonizers of all kinds are scarce in the blast area. There are few food resources: few plants or plant remains and thus few animals. My impression is that many of the invading invertebrates are predatory forms, an observation that agrees with findings at other sites highly altered by such agents as fire. Colonizers often include a high proportion of carnivores because primary plant productivity is lower than in better developed ecosystems. Collecting insects and spiders in the blast zone with any quantitative certainty, however, has been difficult since there is so little life of any sort. The exceptional places, such as the series of protected oases near Spirit Lake, are so small that I do not want to alter them by intensive study techniques.


(Many factors, including chance, influenced the survival of plants and animals after the May 1980 eruption. In most of the blast zone, for example, devastation was nearly total, but the arms of Spirit Lake are dotted by a dozen or so oases -- patches of vegetation a few yards across -- that survived intact and now contain a normal mix of organisms. In other areas, only some species survived, and the composition of the community changed. Around Meta Lake, for instance, gophers survived the eruption but most plant life did not; unable to find food, the gophers had disappeared by the summer 1981.)


In some parts of the blowdown zone, moving among the tangled trunks is so hard that collecting, observing, or even laying out study plots is a challenge. Deer and elk, however, were seen in blowdown areas within days of the May 18 eruption, and they continue to make forays through the area. These large mammals have also been sighted in mountain basins just north of Spirit Lake, more than five miles from normal vegetation. When they find no food, they simply leave. If they do come across a patch of vegetation, the damage they cause by browsing can be traumatic for the plants and the creatures dependent on them.


America's cosmopolitan deer mouse occurs in a few blowdown sites. In some, where the Soil Conservation Service has attempted to stabilize the soil by seeding with grasses and forbs, high population densities have developed. Gophers, on the other hand, are on the decline in many places. These small mammals feed on bulbs and other belowground plant parts. The roots of such plants as bracken fern and fireweed, often the most conspicuous survivors, do not supply the necessary nutrition. Other, more suitable plants have not yet returned in great enough numbers to support gophers.


In the high-ashfall sites, insects and spiders are abundant and seem to represent a normal admixture, except for ground dwelling forms. Small wolf spiders (Lycosidae) are common in high-ashfall; other ground dwellers have not fared so well. Although in reduced numbers, the same species of small mammals, as well as plants and many other animal groups, occur in heavily ashed areas today as during preeruption times. Our pocket gopher data, for example, suggest population densities lower than at other places we have studied, and our marked population, lacking adequate food here as in blast and blowdown sites, may be declining slightly.


Birds are so mobile that their potential for reestablishment on the volcano is nearly unlimited. Some food exists, in the form of seeds and insects. In some areas, the reseeding projects have produced a considerable food supply for birds that can utilize grass seeds. Many of the bird species inhabiting Mount St. Helens' forests before the eruption, however, were conifer-seed eaters or insectivorous. For these birds, food is less abundant. Nevertheless, on a given day, a few birds can be seen flying overhead almost anywhere on the volcano. In the crater itself, helicopter pilots have reported that hummingbirds have dive-bombed their orange flight suits and the ubiquitous red plastic markers of geologists and biologists.


Establishing that birds are breeding on a site is more difficult than just compiling a list of sightings. Hole-nesting species, which require tree snags, might be expected to do well in the blowdown zone -- if they could find food. Similarly, ground-nesting species might not find the ash too much of a problem. We have noted refous hummingbirds, a raven, and a sparrow hawk in our plots in the blowdown area, but the birds we have seen most often on our early morning censuses of these sites are Oregon juncos (ground nesters) and mountain bluebirds (hole nesters.) In the high-ashfall area twenty miles northeast of the crater, we have found nests and eggs of the junco. For one such site, we estimated, in midsummer 1981, more than sixty birds per twenty-five acres, mostly Oregon juncos and robins but also orange-crowned warbiers, pine siskins, blue grouse, three species of woodpecker, varied thrush, and Townsend's solitaire. The site had been clear-cut some time ago and planted with conifers, which are now about six feet tall and growing out of six inches of ash. A mature forest adjacent to the clear-cut area, also heavily ash covered, contained eleven species and about thirty birds per twenty-five acres. These species lists and densities are not out of line with expectation for similar sites unaffected by the volcano.


I have not spent much time studying aquatic habitats on the mountain. In September of 1980, I visited temporary ponds in Mosquito Meadow in the high-ashfall area. They contained salamander and toad larva that were about to transform, as well as a garter snake. In May of 1981 , these ponds were full of breeding salamanders of two species, the long-toed salamander (Ambystoma macrodactylum) and the northwestern salamander (Ambystoma gracile.) Jim Seddell of the U.S. Forest Service Laboratory at Corvallis, Oregon, has been studying streams in the blast area and has, for some sites, lists of species similar to normal situations. Among the species are insects, fishes, the tailed frog (Ascaphus truei), and the Pacific giant salamander (Dicamptodon ensatus.) Muskrats, trout, mink, and newts (Taricha sp.) have persisted in some lakes -- for example, Ryan Lake, also in the blast zone.


In addition to determining what animals now reside on the mountain, and in what numbers, Doug Andersen and I are attempting to test some hypotheses about the role of animals in the process of ecosystem succession. Working in a clear-cut, high-ashfall site, we are particularly interested in the impact of small mammals and ants on plants and soil. Studies of succession in the subalpine habitats of Utah have generated some specific and some general hypotheses about the sequence of events following disturbance to the landscape. For example, animals, as dispersers of seeds and fungal spores, may influence the presence or absence of some plant species. Currently, I am also testing these hypotheses on sites altered during the process of strip mining. My assumption is that ecosystem recovery processes should be similar regardless of the disturbing agent -- fire, grazing, clear-cutting, or mining -- and that observing the processes in both managed and unmanaged situations should increase the ability to repair ecosystems effectively. When Mount St. Helens erupted, we recognized in the volcano a natural laboratory that might allow us to test some of our ideas, on a scale that no federal or private funding could underwrite and in areas much like the sites I was studying in Utah.


A final report of our finds would be premature, but the pocket gopher, our favorite beast, seems to be living up to our expectations. Gophers consume the underground portions of plants: bulbs, corns, roots, and rhizomes. In the winter, gophers fill snow tunnels with soil, and melting snowpack discloses ribbons of disturbed soil on the ground and a disk of freshly overturned soil around the burrow openings. These very characteristics were the basis for our postulation that gophers might have a positive role in the reestablishment of ecosystems on Mount St. Helens. First, gophers were good candidates for being survivors. Assuming that, even in the blast area, heat from deposited materials was not too great, some of these fossorial animals might persist in otherwise barren landscapes, at least until they exhausted their belowground food resources. This has been the case, and we have found gophers in areas representing most types of damage, including blast, blowdown, and high-ashfall areas.


Second, we thought the soil-turning proclivities of gophers might be beneficial. If well-developed soil was trapped under volcanic material, the gophers, just like a plow, might turn over the fresh and inert ash material and mix it with the old soil. This is occurring, but at a slow rate because so many gophers have died since the eruption for lack of the right plants to eat. Where mixing is taking place, our prediction seems to be borne out. In the summer of 1981, soil turned over by gophers had more seedlings growing on it than did adjacent volcanic material not mixed by the animals.


There are many reasons why this might be the case. The buried soil contains more organic matter and various chemical nutrients than does the new material deposited by the eruption. The tilling activities of gophers might also make possible an important association that many higher plants form with a group of fungi known as mycorrhizae. This association may increase the plants' ability to get nutrients and water from the soil and may be critical to the survival of some species. Mycorrhizal spores are not as easily disseminated as those of other fungi. Several studies implicate small mammals, such as rodents and rabbits, and insects, such as grasshoppers, as dispersing agents.


Most well-developed soils contain the desirable mycorrhizae, but covered by ash, these soils might be ineffective. In an analogous situation -- where topsoil stripped from coal mine sites is stored in large piles until mining is completed -- mycorrhizae have been shown to decline with the time stored in the pile. The stored soil thus becomes an even poorer potential growth medium. On Mount St. Helens, the gophers' digging activities appear to rescue spores from the old soil and mix them into the ash material, increasing the ability of the mixture to act as a growth medium. In tests, samples of soil processed by gophers contain forty to eighty spores per grams of dry soil, while the adjacent volcanic material had an average of less than one spore per gram of dry soil.


I do not mean to imply that gophers will be the main factor in the regeneration of the whole volcanically altered landscape, only that like all organisms, they have an influence, no matter how small. Mount St. Helens, recently reduced to a science fiction caricature of the surface of a planet, is very much a functioning, natural ecosystem in which the rules of the biosphere operate. Careful study of the varying abilities of different plants and animals to exist on the new Mount St. Helens is leading to insights on the varying roles these organisms have in the recovery of the volcano's ecosystems. Some of these insights. especially when combined with studies of undisturbed ecosystems, may help humans, users of various landscapes, approach management problems.

James A. MacMahon is a professor of biology and a member of the Ecology Center at Utah State University.

Mount St. Helens Revisited #2

With few exceptions, sportsmen should be able to enjoy their outdoor pastimes this fall much as they have in past years.


by Dick Bolding


Reprinted from Washington Wildlife, Fall 1980.


The blasted, monochromatic landscape littered with charred, denuded tree trunks has a kind of sterile beauty. But it's hard to look at the land around Mt. St. Helens without longing for the majestic forest that covered these ridges and valleys before the volcano's catastrophic eruption. Few who hunted elk in its forests or fished for steelhead in its pristine rivers can help but compare this biological desert with the magnificent vistas of a few months ago.


Yet the future for wildlife here is not quite as dim as it seemed during the first stunned weeks after the mountain's devastating May 18 explosion. Most recent observations by wildlife scientists around the state have been a source of optimism.


There's no denying that in the immediate vicinity of the volcano wildlife and wildlife habitat will take a long time to recover. But farther away from the mountain there have already been signs that nature is healing her wounds.


Wildlife biologist Rich Poelker recently flew into the blast zone about 10 miles north of the volcano, near the junction of Grizzly Creek and the upper Green River, just beyond Mount Margaret. He found a timber graveyard--tangled bodies of giant old-growth fir trees and occasional stands of dead, heat-seared trees. Flash-flooding left deposits of ash-laden mud in this part of the upper Green and its tributaries, and ash covers the ground in a layer that varies from two to six inches deep. While Poelker was there, he saw no living thing. But when he moved just three miles downstream, he found plants sprouting through the ash blanket at the rate of some 8,000 per acre and saw many deer and elk tracks.


Other observers have seen sprouting vegetation along mudflows that choke the north and south forks of the Toutle River. Streams are beginning to erode through the volcanic debris to the harder surfaces of the stream beds below. Upriver much of the fine silt has been washed away, and the water is already clear, although it gets progressively murkier downstream.


Fish biologists reported that some aquatic insects in the streams survived the disaster--a sign that bodes well for all the species that depend on these insects for food. Surprisingly, some observers have even reported seeing steelhead that have made their way upstream on the main Toutle, and fish are moving freely up the Cowlitz River, which was blocked by mud and volcanic debris just a couple of months ago.


Deer and elk are showing up in the valley bottoms with a nearly normal proportion of young. The animals seem to be in good condition, but biologists are quick to point out that they have yet to face the critical winter months, when food will be in short supply. And winter rains could reverse the recovery process, severely eroding the untimbered slopes and scouring the valleys. Floods could prove disastrous to the rebuilding fishery and jeopardize this year's wildlife production.


Many high lakes within the blast zone are filled with ash and debris from the eruption, and some even had most of their water blown out by the concussion. Although the fisheries in these lakes were obviously destroyed, biologist Bruce Crawford found plankton--the microscopic organisms that directly or indirectly support all aquatic life--still living in what was left of some of them. In Hanaford Lake, about 120 miles northeast of the mountain, he found a live female crawfish. He theorizes that, barring further destructive eruptions, the food chain may recover enough to support fish in some of these lakes in two or three years.


Because most ash from the eruptions drifted north and east from the volcano, lakes on the mountain's southwest side suffered little damage. Merrill Lake, Mc-Bride Lake, Kalama Springs, and Blue Lake all contain fine ash, but it has not, so far, significantly affected their fisheries.


High lake fisheries suffered the most damage in areas that received moderate to heavy ash falls. Ash smothered the bottom-dwelling insects on which fish feed and filled the spaces between the pebbles and rocks of the lake bottoms, eliminating the insects' habitat. No doubt many fish suffered fatal gill damage from the exposure to suspended ash particles in the water.


Outside the blast zone, toward the east, the depth of the ash blanket varies, as does the particle size. Rain has washed most of the gray mantle from trees and bushes, but ash still covers the ground. Blue Lake, 22 miles northeast of St. Helens, is surrounded by a heavy ash cover, but the lake water is still blue and clear. Ten miles farther east, Walupt Lake got a two- to four-inch accumulation of sand-like ash; here Game Department and Forest Service personnel found lake water temperatures and acidity to be normal. Bottom-dwelling invertebrates were reduced as a result of the ash, but not seriously. Biologists collected 32 rainbow trout, several cutthroat and 200 crayfish from the lake and found them all in good condition.


At Packwood Lake, 12 miles north of Walupt, conditions are much the same. The ash that fell here was finer, and it remained in suspension in the water longer, reducing the production of microscopic life. But enough aquatic insects survived to provide fish with an adequate food supply. Just southeast of Packwood Lake Poelker saw a band of 23 elk--10 of them calves--and on a high ridge above Smith Creek, a few miles to the west, he counted five ash-colored mountain goats.


Still farther east, ash fallout painted a 50-mile-wide band across the Cascade crest as it moved northeasterly toward Spokane. Most high lakes along the crest that got ash have not been scientifically monitored to assess the effects on their fisheries, but preliminary observations suggest that most have not been much affected. Some lakes without strong outlet currents seem murky from the suspended ash particles, but most lakes in this area have been providing their usual fishing--even those that are slightly off-color.


East of the Cascades, the Yakima County high country got an average of about an eighth of an inch of ash. The heaviest deposits were along the upper Tieton River south of White Pass, where the ash measures nearly an inch. Even so, regional Game Department biologist Ellis Bowhay has reported frequent big game sightings in the area, including observations of many young deer and elk.


After the May 18 eruption and ash fall, the first thing Bowhay and most other east-side observers had noticed was the loss of insects. Most young birds had just hatched or were about to hatch and were almost entirely dependent on insects for food. In some places, Bowhay said, hundreds of young cliff swallows were found lying dead on the ground below nest sites, apparently as a result of starvation, and the situation was much the same for many other songbirds.


As the summer progressed, wildlife inventory crews reported seeing fewer rodents and small animals than in past years. Their observations confirmed that, of all the wildlife, small birds and mammals were hardest hit by the eruptions.


Far more encouraging has been the frequency of upland bird sightings in eastern Washington. Immediately after the May 18 eruption, biologists reported that in some areas up to 85 percent of the pheasant hens were driven to abandon their nests. They feared that even if upland birds were to successfully renest, the survival of the newly hatched young would be limited by the reduced number of insects.


But counts of pheasant, quail and chukar broods in the Yakima region appeared to be as good as they were during some high population years. The counts were so good, in fact, that Bowhay confesses he's a little nervous about the effects of the reduction of insects and the habitat's capacity to support the birds through the winter. He attributed the good bird production to an apparently high rate of second nesting attempts. Heavy spring rains stimulated a more luxuriant growth of range grasses which lasted longer than usual into the dry summer months, providing good cover for nesting birds.


The high incidence of renesting by pheasants during the summer has resulted in more younger birds than most years, so hunters this fall will shoot greater-than-normal numbers of mature roosters


Similar fears about losing this year's upland bird production in the Columbia Basin have also proven unnecessary. High brood counts and the gradual comeback of insects in the Basin are good omens for this year's upland bird season.


Likewise, the lack of terrestrial insects during the height of eastern Washington's spring hatch apparently did little harm to waterfowl populations. Aquatic organisms furnished enough protein to carry small ducklings through their early days of life until they could forage for a wider variety of foods.


However, inventories of duck populations in nesting grounds throughout western Canada are a little lower than usual due to the effects of short water supplies on nesting and hatching survival. That means fewer ducks migrating through during hunting season. But although production is somewhat less than last year, it has not dropped enough to require any reduction in hunters' bag limits.


So, while there can be no doubt about the loss of wildlife and destruction of habitat near the volcano, short-term investigation seems to show that the effects of ash fallout beyond the blast area are not as severe as biologists had earlier feared. That's good news for sportsmen and other outdoor recreationists who should be able to enjoy wildlife-related activities this fall much as in past years.


Of course, there are some exceptions. The area around Mount St. Helens will be closed indefinitely to all recreation, as will most of the Gifford Pinchot National Forest. As for central and eastern Washington, the ash should prove not more than a discomfort and an inconvenience for outdoorsmen. It shouldn't seriously hamper their activities. Bird dog trainers, for instance, report that working their dogs in the volcanic dust has had no apparent ill effects on their dogs. Those living in ash-fall areas say the ash will be with us for a few years--we'll just have to put up with it.


As it turns out, the May 18 eruption was not the end of the world, nor will it seriously limit hunting and fishing opportunities in our state. And while there may be more eruptions in the future, we know now that we can deal with the aftermath, and so can our wildlife.

Mount St. Helens Fact Sheet

(Copied by permission from publication of Mount St. Helens National Volcanic Monument and Gifford Pinchot National Forest. Activity and Chronology are through March 1984.)



Background Information


    Fifty miles from Portland, Oregon, in the Gifford Pinchot National Forest in the State of Washington.



    Summit elevation now approximately 8,300 feet. Original height before eruption, 9,677 feet.


Last Eruption:

    Last eruption from early 1800's until 1857. Dormant for 123 years until March 27, 1980.


Other Active Volcanoes:

    First volcanic eruption in continental 48 states since Lassen Peak in California last erupted from 1914 to 1917.




    From March 27 through May 17, 1980, consisted of steam and ash, with some small mudflows. On May 18, a violent eruption began when an earthquake triggered a giant landslide that removed the northern flank of Mount St. Helens. The blast, accompanied by hot gasses, pumice, and ash, devastated more than 150 square miles in a broad sector north of the mountain, with all trees and vegetation laid flat or killed. The highest ash cloud reached at least 70,000 feet and was tracked around the world. Ash fallout was heavy and crippled cities - Yakima, Washington, 85 miles away received 5/8 inch; Spokane, Washington, 255 miles - 1/8 inch; Pullman, Washington/Moscow, Idaho, 260 miles - 1/5 inch; and Ritzville, Washington, 195 miles - 2 inches.

    The eruptions of May 25, June 12, and October 16, which were accompanied by some pyroclastic flows, left 1/8 to 1/2 inch of ash on Vancouver, Southwestern Washington, and Portland, Oregon.

    The first dome of crusty, volcanic lava was observed after the June 12 eruption. This dome was destroyed by the July 22 eruption. A second dome, observed on August 8, was destroyed by the October 16 eruption and a third was observed forming on October 18. A non-explosive event occurred December 27, 1980 - January 4, 1981, adding two additional lobes to the October dome. Non-explosive eruptions beginning February 5, April 10, June 18, September 6, and October 30, 1981, added new extrusions to the pre-existing composite dome. The next eruption began March 19, 1982, with moderate explosive activity, accompanied by mudflows, followed by the extrusion of two additional lobes of lava on the dome and further small explosive events. Two subsequent non-explosive events, May 14 and August 17, added new lobes to the existing dome. The mountain remains calm with minor steam plumes and low-level seismic activity.


Fatalities: 36

Missing People: 21



    The May 18 eruption left a crater approximately 1 mile wide and 2 miles long. An estimated 1 cubic mile of rock or 12 percent of the mountain was removed during the eruption. Elevation of the mountain was reduced by approximately 1,370 feet from 9,677 to 8,307 feet. Landslides from the crater walls continue to occur periodically.




    From March 20 to May 18, over 2,400 earthquakes of magnitude 2.4 or greater occurred, of which 371 were over 4.0. Strongest to date: 5.1 on May 18. Earthquakes have subsided considerably since May 19, but vary with the degree of eruptive activity.




    Mudflows and flooding caused extensive damage downstream from the area.


Resource Losses:


    The May 18, 1980 eruption severely damaged 61,200 acres of National Forest land and 89,400 acres owned by the State of Washington, private interests, and individuals. National Forest resources damaged or destroyed include: 1.6 billion board feet of timber; 100 miles of streams; 2,300 big game animals; 27 recreation sites; 63 miles of road; 13 bridges; 197 miles of trails; and 15 Forest Service buildings. Estimated resource loss on National Forest lands: $134,087,000.


Potential Hazards:


  1. Probable ash and steam eruptions.
  2. Rapidly moving flows of mud (melting snow and ice mixed with ash).
  3. Pyroclastic flows, which are masses of fiery gasses and light-weight volcanic particles that skim like an avalanche along and above the ground at speeds of up to 100 miles per hour.
  4. Ashfall carried by prevailing winds as a result of a major eruption.
  5. Flooding.


Chronology of Events

March 20, 1980
First earthquake of magnitude 4 reported. The number of earthquakes gradually increased during the succeeding week suggesting impending volcanic activity.

March 27, 1980
First eruption of steam and ash. Similar explosions continued until about April 22.

May 7, 1980
Eruptions of steam and ash resumed and continued until May 14.

May 18, 1980
Huge landslides and associated violent explosive eruption, accompanied by mudflows, pyroclastic flows, flooding, and extensive ash deposits.

May 25 through October 16
Series of 5 separate ash eruptions accompanied by pyroclastic flows. Lava dome destroyed by eruption on October 16.

October 18 & 19
A new lava dome grew in crater.

December 27, 1980, February 5, 1981, April 10, 1981, June 18, 1981, September 6, 1981, October 30, 1981
Last major ash eruption occurred October 16, 1980, but since that time there have been several non-explosive (minor ash) eruptions, each adding a portion to the pre-existing composite dome formed during the October eruption.

March 19, 1982 Dome-growth eruptive phase with minor explosive events and small mudflows, adding two new lobes to the pre-existing dome. Continued until April 12, 1982.

May 14, 1982, August 17, 1982
Non-explosive (one minor and one no-ash) eruptive phases, May 14-20 and August 17-23, added new lobes on the northwest and south-southwest sides of the composite dome.

February 1983 to March 1984
This period was marked by a slow, continuous addition of lava to the dome. Size of the dome, March 1984: 800 feet high, by approximately 2500 feet across. (Check with Monument Headquarters for latest dimensions.)

From Lava to Life

by Donna Gleisner and Bruce Crawford


Reprinted from Washington Wildlife, Fall 1980.


No one suspected that Mount St. Helens would utterly devastate 100,000 acres of the Cascade Mountains on that calm Sunday morning, or that it would happen with such force in just a matter of minutes. A 100-400 mile per hour lateral blast from the north face seared the surrounding countryside and alpine lakes with temperatures of up to 500 degrees F and engulfed all life in a deadly blanket of fallout.


All 37 lakes within the Mount St. Helens National Volcanic Monument received the full brunt of that natural, yet terrifying, phenomenon. The blast's destructive forces denuded most shorelines of anything green and growing. In their place settled a layer of hot, gray ash that choked off light and life and superheated the waters.


At that time the lakes, all managed by the Washington Department of Game for trout fishing, contained a mixture of eastern brook and cutthroat trout. Most lakes were planted by helicopter or plane on a three-year rotation basis. Fifty to 100 fish per acre was the norm, meaning that as many as 150,000 fish could have been in the lakes at eruption time.


Conditions looked extremely dismal immediately after the blast. The suspension of ash in the lakes along with super hot temperatures severely reduced the aquatic plants and animals abilities to survive. But to find out exactly what the conditions were in the blast zone, biologists from state and federal agencies decided to helicopter in as close as they dared, starting in July. This was the beginning of four years of research.


From July 1980 through August 1984, 21 lakes were surveyed by the Washington Department of Game. Surprisingly enough, live populations of trout were found in two-thirds of them: Elk, Fawn Hanaford, Island, Little Venus, Merrill, Meta, Obscurity, O'Connor, Panhandle, Shovel, Strawberry, Tradedollar and Venus. Of the seven remaining lakes where gill net surveys failed to produce fish, only three lakes -- Boot, Ryan and Spirit -- appear to have lost their populations due to the eruption of Mount St. Helens. Two of the seven barren lakes sampled probably didn't contain any fish prior to the eruption because they were too shallow.


Of those waters with surviving populations, eastern brook trout were either the dominant or the only fish species found in most. Cutthroat were found in only four lakes and lake trout in one. it seems that in the lakes where cutthroat were stocked on top of self-sustaining brook trout populations, only brooks survived the stress and competition imposed by the blast.


The good news is that many lakes still retain the habitat needed for natural spawning to take place in inlet or outlet streams. And evidence so far indicates that eastern brook trout are again successfully spawning in at least three lakes and cutthroat in one lake. The reason? Aquatic insects somehow managed to survive the blast's effects or quickly repopulated the devastated lakes. Just that little bit of life, plus the self-cleansing action of the water itself, enabled life in those lakes to respond rather quickly -- in one to three years. Now aquatic life, including fish, is rapidly approaching, and in some lakes even exceeding, its preeruption population levels.


Selected lakes outside the Monument, such as Hanaford, were stocked beginning as early as 1982 and receive quite a bit of use. But within the Monument itself, a five-year moratorium on stocking fish is in effect. This allows researchers time to complete their studies before fish are reintroduced on an artificial basis.


Bruce Crawford, regional fish biologist for the Department of Game, believes that all natural lakes, including Spirit lake with its abnormally high nutrient levels, are very capable of sustaining populations of trout. He also thinks the two newly-formed lakes, Castle and Coldwater, are capable of doing the same on an even larger scale.


The future of these alpine lakes and their fish populations depends upon proper management and adequate public access -- something that the Washington Department of Game and the Gifford Pinchot National Forest are working closely together on. We want to not only meet the recreational needs of our sport fishing public, but to also remain aware of the unique research opportunities and the fragile life within that seeming desert of ash.

Donna Gleisner is a Department of Game Conservation Education Programs Specialist and Bruce Crawford is a Regional fish Biologist, both in Region Five, Vancouver.

The Eruptive History of Mount St. Helens

The Eruptive History of Mount St. Helens

by Donald R. Mullineaux and Dwight R. Crandell




The eruptive history of Mount St. Helens began about 40,000 years ago with dacitic volcanism, which continued intermittently until about 2,500 yr ago. This activity included numerous explosive eruptions over periods of hundreds to thousands of yr, which were separated by apparent dormant intervals ranging in length from a few hundred to about 15,000 yr. The range of rock types erupted by the volcano changed about 2,500 yr ago, and since then, Mount St. Helens repeatedly has produced lava flows of andesite, and on at least two occasions, basalt. Other eruptions during the last 2,500 yr produced dacite and andesite pyroclastic flows and lahars, and dacite, andesite, and basalt airfall tephra. Lithologic successions of the last 2,500 yr include two sequences of andesite-dacite-basalt during the Castle Creek period, and dacite-andesite-dacite during both the Kalama and Goat Rocks periods. Major dormant intervals of the last 2,500 yr range in length from about 2 to 7 centuries.


During most eruptive periods, pyroclastic flows and lahars built fans of fragmental material around the base of the volcano and partly filled valleys leading away from Mount St. Helens. Most pyroclastic flows terminated with 20 km of the volcano, but lahars extended down some valleys at least as far as 75 km. Fans of lahars and pyroclastic flows on the north side of the volcano dammed the North Fork Toutle River to form the basin of an ancestral Spirit Lake between 3,300 and 4,000 yr ago during the Smith Creek eruptive period, and again during the following Pine Creek eruptive period.




The eruptive history of Mount St. Helens is subdivided here into nine named eruptive "periods," which are clusters of eruptions distinguished by close association in time, by similarity of rock types, or both. The term "eruptive period" is used in an informal and largely arbitrary sense to divide the volcano's history into convenient units for the purpose of discussion. The periods are as much as several thousand years in duration, and include what may have been a single group of eruptions as well as extended episodes of volcanism, during which there were tens or possibly hundreds of eruptions. Eruptive periods are separated by apparently dormant intervals, which are inferred chiefly from buried soils and absence of eruptive deposits. However, some dormant intervals may span times of minor activity that did not produce deposits which can now be recognized. Fine-grained, air-laid volcanic detritus was deposited during some dormant intervals, but these deposits are not known to have originated directly from eruptions; they might be material reworked from the flanks of the volcano. 


The stratigraphic record of eruptive activity during the last 13,000 yr is believed to be reasonably complete. Parts of the older record, however, apparently are missing because of glacial and stream erosion during the last major glaciation (the late Pleistocene Fraser Glaciation) of the region.




The first stratigraphic evidence of the existence of Mount St. Helens consists of voluminous dacitic deposits of slightly vesicular to pumiceous air-fall tephra and pyroclastic flows, and at least one pumice-bearing lahar. These deposits overlie extensively weathered glacial drift formed during the next-to-last alpine glaciation of the Cascade Range. The volcanic deposits were formed during at least four episodes, separated by intervals during which very weak soils developed. The entire eruptive period may have extended over a time span as long as 5,000 yr. One pumiceous tephra deposit produced during the period probably had a volume as great as that of any subsequent tephra erupted at Mount St. Helens. 


The Ape Canyon eruptive period was followed by a dormant interval which may have lasted from about 35,000 to 20,000 yr ago. Most of this 15,000-yr interval coincided with climates which, at times, were evidently somewhat cooler than those of the present (Alley, 1979, p. 233).




The second eruptive period probably began about 20,000 yr ago, and was characterized by the eruption of small volumes of pumiceous dacite tephra; it also produced lahars, pyroclastic flows of pumiceous and lithic dacite, a few lava flows of dacite or high-silica andesite (C.A. Hopson, written commun., 1974), and perhaps one or more dacite domes. Several different eruptive episodes can be identified during the period. At least one pumiceous pyroclastic flow moved southward to at least 16 km from the center of the present volcano about 20,350 yr ago (Hyde, 1975, p. B11-B13). Two sequences of air-fall tephra that followed (sets M and K) are separated by a two-part deposit of fine air-laid sediment that locally is a meter or more thick, and that contains at least one weakly developed soil. After another quiet interval during which there was a small amount of soil development, at least two more pyroclastic flows moved south and southeast from the volcano between about 19,000 and 18,000 yr ago. The Cougar eruptive period occurred during the Frasier Glaciation when alpine glaciers in the Cascade Range were at or near their maximum extents, and the products of eruptions generally are poorly preserved.


One lahar that apparently occurred early in the Cougar period is of special interest because of some similarities to the debris avalanche of May 18, 1980, that swept down the North Fork Toutle Valley. The lahar of Cougar age consists of an unsorted and unstratified mixture of gray dacite fragments in a compact matrix of silt and sand as much as 20 m thick. Locally, it contains discrete texturally similar masses of red dacite many meters across. The iron-magnesium mineral content of rocks in the lahar is similar to that of the Ape Canyon period, suggesting that the lahar might have been derived from older parts of the volcano. The lahar was recognized in the Kalama River drainage 8 km southwest of the center of the modern volcano, and on both walls of the Lewis River valley near Swift dam (Hyde, 1975, p. B9-B11). It has not been recognized elsewhere; thus, little is known of its original extent. Its local thickness and heterolithologic character suggest that the lahar might have originated in a large slope failure on the south side of the Mount St. Helens of early Cougar time.

There is no stratigraphic record of volcanism at Mount St. Helens between about 18,000 and 13,000 yr ago.




The third eruptive period was characterized by repeated explosive eruptions that initially produced many pyroclastic flows as well as pumiceous air-fall tephra deposits, some of which had large volumes and extended at least as far east as central Washington. These eruptions of dacite pumice were followed by many lithic pyroclastic flows, which are believed to have been derived from domes; at least one of these pyroclastic flows reached a point 21 km from the center of the present volcano. The pyroclastic flows were followed, in turn, by another series of explosive eruptions that produced the voluminous tephra set J. One coarse pumice layer of set J extends west-southwest from Mount St. Helens, and is as much as 20 cm thick as far as 20 km from the volcano. The layer represents the only coarse and thick pumice known to have been carried principally in a westerly direction. The sequence of explosive eruptions that formed set J apparently ended the Swift Creek eruptive period sometime before 8,000 yr ago, and was followed by a quiet period of at least 4,000 yr.




Multiple explosive eruptions of the Smith Creek eruptive period, which began about 4,000 yr ago, initiated at least 700 yr of intermittent and at times voluminous eruptive activity. Three coarse pumice layers at the base of tephra set Y are overlain by layers of denser, somewhat vesicular tephra. Deposition of these units was followed by an interval during which a soil began to develop on the tephra. The next eruption of the period produced the most voluminous and widespread tephra deposit of the last 4,000 yr; it is one of the largest, if not the largest, in the history of the volcano, and has an estimated volume of at least 3 km. The resulting pumice layer, Yn, has been found nearly 900 km to the north-northeast in Canada (Westgate and others, 1970, p. 184). The formation of this layer was followed shortly by another voluminous eruption of tephra, which resulted in layer Ye (Mullineaux and others, 1975, p. 331), then by a pumiceous pyroclastic flow and a coarse lithic pyroclastic flow. The lithic pyroclastic flow was accompanied by clouds of ash that spread at least a kilometer beyond the sides of the flow and as much as 2 km beyond its front. Many smaller eruptions of lithic and moderately vesicular ash and lapilli followed, perhaps within a few years or tens of years.


Lahars and pyroclastic flows of Smith Creek age formed a fan north of the volcano, and lahars extended down the North Fork Toutle River at least as far as 50 km downvalley from Spirit Lake. An ancestor of the lake probably came into existence at this time, dammed in the North Fork valley by the fan of lahars and pyroclastic-flow deposits. It is not known if the lake ever existed before Smith Creek time.

A dormant interval of apparently no more than a few hundred years followed the Smith Creek eruptive period.




Although only a short time elapsed between the Smith Creek and Pine Creek periods, eruptive products of Pine Creek age contain an iron-magnesium phenocryst assemblage that is distinctly different from those of Smith Creek age. During the Pine Creek eruptive period, large pumiceous and lithic pyroclastic flows moved away from the volcano in nearly all directions. The lithic pyroclastic flows, some of which extended as far as 18 km from the present center of the volcano, are believed to have been derived from dactic domes. Eruptions of dactic airfall tephra were of small volume, but at least four formed recognizable layers as far away as Mount Rainier (Mullineaux, 1974, p. 36).


During this time, lahars and fluvial deposits aggraded the valley floors of both the North and South Fork Toutle River, and created the basin of Silver Lake 50 km west-northwest of the volcano by locking a tributary valley (Mullineaux and Crandell, 1962). Similar deposits also formed a contiguous fill across the floor of the Cowlitz River valley near Castle Rock that was about 6 m above present river level; this fill probably extended 209 km farther to the mouth of the Cowlitz River.  Lahars and fluvial deposits formed a similar fill in the Lewis River valley which, near Woodland, was about 7.5 m higher than the present flood plain (Crandell and Mullineaux, 1973, p. A17-A18).


The eruptions of Pine Creek time extended over a period of about 500 yr. No single eruption of very large volume has been recognized from deposits of Pine Creek age, and the period seems to have been characterized by many tens of eruptions of small to moderate volume and the growth of one or more dacite domes. Some radiocarbon dates on deposits of Pine Creek and Castle Creek age overlap, and if the two eruptive periods were separated by a dormant interval, it must have been short.




The next period of activity marked a significant change in eruptive behavior and variety of rock types being erupted at Mount St. Helens. During the Castle Creek eruptive period, both andesite and basalt were erupted as well as dacite, and these rock types evidently alternated in quick succession. The overall sequence includes, from oldest to youngest, andesite, dacite, basalt, andesite, dacite, basalt.


Thus, the stratigraphic sequence of Castle Creek time is complex, and not all stratigraphic units are represented on all sides of the volcano. Northwest of Mount St. Helens, in the Castle Creek valley, the sequence preserved includes the following:

Lava flow of olivine basalt (youngest)

Lava flow of hypersthene-augite andesite

Tephra deposit of olivine-augite andesite scoria (layer Bo)

Pyroclastic-flow deposits of hypersthene-dacite pumice

Tephra deposit of hypersthene-augite andesite scoria (layer Bh)

Lava flow and lahars of hypersthene-augite andesite (oldest) 


The pumiceous pyroclastic-flow deposits have a radiocarbon age of 2,000-2,200 yr. Deposits and rocks of Castle Creek age on the south and east flanks of the volcano include pahoehoe basalt lava flows whose radiocarbon age is about 1,900 yr, and pumiceous dacite tephra whose age is about 1,800 yr (layer Bi.). East of the volcano, layer Bi overlies a pyroclastic-flow deposit of pyroxene andesite, and directly underlies thin olivine basalt lava flows which probably are correlative with the uppermost unit in the Castle Creek valley. The Dogs Head dacite dome was extruded before those thin olivine basalt flows, probably during the Castle Creek eruptive period. Layer Bu is the youngest tephra of Castle Creek age; it underlies a deposit whose radiocarbon age is about 1,620 yr. This tephra is basaltic and probably was formed when thin olivine basalt lava flows were erupted near the end of the Castle Creek period.


Castle Creek time marked the start of eruptions that built the modern volcano. It is interesting to note that the change in eruptive behavior from that of the preceding 35,000-plus years did not follow a long period of dormancy like several that occurred during Mount St. Helens' earlier history. The dormant interval that followed Castle Creek time apparently lasted about 600 yr.




During the next 1,200 yr, the only eruptions recorded at Mount St. Helens are those associated with the formation of Sugar Bowl, a dome of hypersthene-homblende dacite at the north base of the volcano. During extrusion of the dome, a directed blast carried rock fragments laterally northeastward in a sector at least 50 degrees wide and to a distance of at least 10 km. The resulting deposits are as much as 50 cm thick and consist of ashlapilli, and breadcrusted blocks of dacite from the dome, fragments of charcoal, and stringers of material eroded from the underlying soil. A single fragment of charcoal from within the deposit has a radiocarbon age of about 1,150 yr, whereas a sample of wood charred and buried by the deposit has an age of about 1,400 yr (Hoblitt and others, 1980, p. 556). We provisionally assign an age of about 1,150 yr to the blast deposit; the older date may have been obtained from a fragment of a mature tree that was overridden by the blast.


pyroclastic flow deposit of breadcrusted blocks, as well as prismatically jointed blocks of dacite of the same composition as the dome, was found on the north slope of Mount St. Helens downslope from Sugar Bowl; this pyroclastic flow may have occurred at the time of the lateral blast. Three lahars containing breadcrusted blocks of similar dacite were formerly exposed in the North Fork Toutle River valley west of Spirit Lake. These lahars may have been caused by melting of snow by the lateral blast or by the pyroclastic flow.


East Dome, a small dome of hypersthene-homblende dacite at the east base of the volcano, may have been formed at about the same time as the Sugar Bowl dome. East Dome is overlain by tephra of the Kalama period but not of the Castle Creek period, and could have been formed any time between the Castle Creek and Kalama eruptive periods, a time span of about 1,200 yr. 




Most of the rocks visible at the surface of the volcano before eruptions began in 1980 were formed during the Kalama eruptive period. Although the range in radiocarbon dates and ages of trees on deposits of Kalama age suggest that the eruptive period lasted from nearly 500 to 350 yr ago, all the events described here probably occurred during a shorter time span, perhaps less than a century.


The Kalama eruptive period began with the explosive eruption of a large volume of dacite pumice (layer Wn) which forms the basal part of tephra set W. Layer Wn was deposited northeastward from the volcano across northeastern Washington and into Canada (Smith and others, 1977, p. 209) and was followed by additional pumice layers. At about the same time, pyroclastic flows of pumiceous and lithic dacite moved down the southwest flank of the volcano. The relative timing of these events is poorly known because most of the air-falltephra was carried eastward and northeastward, whereas the pyroclastic flows have been found only on the southwest flank of Mount St. Helens.


A short time later, scoriaceous tephra of andesitic composition was erupted. In addition, andesite lava flows extended down the west, south, and east slopes of the volcano, and andesite pyroclastic flows moved down the north, west, and south flanks.


These eruptions of andesite were followed by the extrusion of the dacite dome that formed the summit of the volcano before the May 18, 1980, eruption.  Avalanches of hot debris from the dome spilled down over the upper parts of the preceding lava flows, and some of this hot debris partly filled channels between levees of the andesite lava flows on the south side of the volcano (Hoblitt and others, 1980, p. 558). Late in this eruptive period, a pyroclastic flow of pumiceous dacite moved northwestward from the volcano down the Castle Creek valley and covered lahars of summit-dome debris. Charcoal from the pyroclastic-flow deposit has a radiocarbon age of about 350 yr (Hoblitt and others, 1980, p. 558).


The Kalama eruptive period was characterized by frequent volcanism of considerable variety; rock types being erupted alternated from dacite to andesite and back to dacite, and the volcano grew to its pre-1980 size and shape. The eruptive period was followed by a dormant interval of about 200 yr.




The Goat Rocks eruptive period began about A.D. 1800 with the explosive eruption of the dacitic pumice of layer T. This pumice was carried northeast-ward across Washington to northern Idaho (Okazaki and others, 1972, p. 81) and apparently was the only eruptive product of that time. Many minor explosive eruptions of the Goat Rocks period were observed by explorers, traders, and settlers from the 1830's to the mid-1850's. The Floating Island Lava Flow (andesite) was erupted before 1838 (Lawrence, 1941, p. 59) and evidently was followed by extrusion of the Goat Rocks dacite dome on the north flank of the volcano (Hoblitt and others, 1980, p. 558).

The last eruption of the Goat Rocks eruptive period was in 1857, when "volumes of dense smoke and fire" were noted (Frank Balch, quoted in Majors, 1980, p. 36). A recent study of old records has suggested that minor eruptions of Mount St. Helens also occurred in 1898, 1903, and 1921 (Majors, 1989, p. 36-41). The published descriptions of these events suggest that they were small-scale steam explosions, and none produced deposits that were recognized in our studies. 




One of the most interesting features of Mount St. Helens' history is the change in eruptive behavior that occurred about 2,500 yr ago. Eruptions of dacite had characterized the volcano for more than 35,000 yr. Then, with virtually no interruption in eruptive activity, andesite and basalt began to alternate with dacite, and not always in the same order. The chemical composition of eruptive products changed gradually during some episodes and abruptly during others. Thus, basalt followed dacite and dacite succeeded basalt; andesite followed dacite of considerably different SiO2 content, and vice versa. Some of these changes in composition of eruptive products are not adequately explained as results of eruption of cyclic sequences of compositionally different magmas derived from successively deeper levels in a larger magma body that differentiated at shallow depth, as proposed by Hopson (1971) and Hopson and Melson (19800. An alternative explanation that fits the stratigraphic record better, suggested by R.E. Wilcox (oral commun., 1974), is that some changes resulted from repeated contributions from more than one magma body, or from different parts of an inhomogeneous magma.


Explosive eruptions of volumes on the order of 0.1 to 3 km have occurred repeatedly at Mount St. Helens during some eruptive periods in the past. This record suggests that a similar sequence could occur during the present period of activity and could result in one or more explosive magmatic eruptions of similar or larger volume than the eruption of May 18. If the lengths of the last two eruptive periods are a valid guide to the future, we might expect intermittent eruptive activity to continue for several decades.


Eruptive History References


Alley, N.F., 1979, Middle Wisconsin stratigraphy and climatic reconstruction, southern Vancouver Island, British Columbia: Quatermary Research, v. 11, no. 2, p. 213-237.

Carithers, Ward. 1946. Pumice and pumicite occurrences of Washington: Washington Division of Mines and Geology Report of Investigations 15, 78 p.

Crandell, D.R., and Mullineaux, D.R., 1973, Pine Creek volcanic assemblage at Mount St. Helens, Washington: U.S. Geological Survey Bulletin 1383-A, 23 p.

_______ 1978, Potential hazards from future eruptions of Mount St. Helens volcano, Washington: U.S. Geological Survey Bulletin 1383-C, 26 p.

Crandell, D.R., Mullineaux, D.R., Miller, R.D., and Rubin, Meyer, 1962, Pyroclastic deposits of Recent age at Mount Rainier, Washington, in Short papers in geology, hydrology, and topography; U.S. Geological Survey Professional Paper 450-D, p. D64-D68.

Crandell, D.R., Mullineaux, D.R., and Rubin, Meyer, 1975, Mount St. Helens volcano; recent and future behavior: Science, v. 187, no. 4175, p. 438-441.

Fulton, R.J., and Armstrong, J.E., 1965, Day 11, in Schultz, C.B. and Smith, H.T. UY., eds, International Association (Union) of Quatemary Research Congress, 7th, 1965, Guidebook of Field Conference J., Pacific Northwest; p. 87-98.

Greeley, Ronald, and Hyde, J.H., 1972, Lava tubes of the /ave Basalt, Mount St. Helens, Washington; geological Society of American Bulletin, v. 83, no. 8, p. 2397-2418.

Hoblitt, R.P., Crandell, D.R., and Mullineaux, D.R., 1980, Mount St. Helens eruptive behavior during the past 1,500 years: Geology, v. 8, no. 11, p. 555-559.

Hopson, C. A., 1971, Eruptive sequence at Mount St. Helens, Washington: Geological Society of America Abstracts with Programs, v. 3, no. 2, p.138.

Hopson, C. A., and Melson, W. G., 1980, Mount St. Helens eruptive cycles since 100 A. D. [abs.]: EOS, v. 61, no. 46, p.1132-1133.

Hyde, J. H., 1975, Upper Pleistocene pyroclastic-flow deposits and lahars south of Mount St. Helens volcano, Washington: U.S. Geological Survey Bulletin 1383-B, 20 p.

Lawrence, D. B., 1939, continuing research on the flora of Mount St. Helens: Mazama, v.12, p. 49-54.

_______ 1941, The 'floating island" lava flow of Mount St. Helens: Mazama, v. 23, no. 12, p56-60.

_______ 1954, Diagrammatic history of the northeast slope of Mount St. Helens, Washington: Mazama, v. 36, no. 13, p. 41-44.

Mullineaux, D. R., 1974, Pumice and other pyroclastic deposits in Mount Rainier National Park, Washington: U.S. Geological Survey Bulletin 1326, 83 p.

Mullineaux, D. R., and Crandell, D. R., 1960, Late Recent age of Mount St. Helens volcano, Washington: U.S. Geological Survey Professional Paper 400-B. p. 307-308.

_______ 1962, Recent lahars from Mount St. Helens, Washington: Geological Society of America Bulletin, v 73, no. 7, p. 855-870.

Mullineaux, D. R., and Hyde, J. H., and Rubin, Meyer, 1975, Widespread late glacial and post glacial tephra deposits from Mount St. Helens, Washington: U.S. Geological Survey Journal of Research, v. 3, no. 3, p. 329-335.

Okasaki, Rose, Smith, H. W., Gilkeson, R. A., and Franklin, Jerry, 1972, Correlation of West Blacktail ash with pyroclastic layer T from the 1800 A. D. eruption of Mount St. Helens: Northwest Science, v. 46, no. 2, p. 77-89.

Smith, H. W., Okasaki, Rose, and Knowles, C. R., 1977, Electron microprobe analysis of glass shards from tephra assigned to set W, Mount St. Helens, Washington: Quaternary Research, v. 7, no. 2, p. 207-217.

Verhoogen, Jean, 1937, Mount St. Helens, a recent Cascade volcano: California University, Department of Geological Sciences Bulletin, v. 24, no. 9, p. 236-302.

Westgate, J. A., Smith, D. G. W., and Nichols, H., 1970, Late Quaternary pyroclastic layers in the Edmonton area, Alberta, in Symposium on pedology and Quaternary research, Edmonton, 1969, Proceedings: Alberta University Press, p. 179-187.