This model is easy to demonstrate and very useful in relating hazards associated with lava flows (or mud flows). However, this model costs more and requires you to order a plastic three-dimensional map. (unless you can come up with a creative alternative...!)
You will need:
raised relief map
($20 plus shipping from Hubbard Scientific, 800-523-5485)
Omni Resources (1-800-742-2677) sells raised relief maps of Mt. Rainier (12 x 18", $8.95), Yellowstone (18x25", $10.95), Naples (Vesuvius)(2x3', $69.95), Catania (Mt. Etna)(2x3', $69.95), and Reunion (27x23", $49.95).
Step 1. The Map
A raised relief map shows shape and size of a volcano without any distortion. This photo shows a raised relief map for the island of Hawaii. The rifts zones of Kilauea and Mauna Loa volcanoes are highlighted with silver tape. In Hawaii eruptions originate at the summit or along the rift zones of the volcano. Purchase (or make) a relief map of a volcano that is of interest to you (perhaps a well known volcano or one near your home or school.
Step 2. The Lava
Molasses is a good substitute for lava. It is more viscous (stickier) than water and will move slowly down the map.
Step 3. The Eruption
Place the map on a table or on the floor. Stand or sit next to it. Place the straw in the molasses and put your thumb over the top of the straw so the molasses stays in the straw. Move the straw over to the relief map. Take your thumb off the top of the straw so the molasses pours out. Gravity will pull the molasses down slope just like it pulls lava down the slope of the volcano.
Step 4. Factors that Influence Lava Flows
This simple model can demonstrate the factors that influence where lava will flow. For example, start your eruptions at the summit or high or low on a rift zone. Vary the amount of lava erupted (one straw full versus several straws). Vary the duration of the eruption (empty the straw at intervals of 5 seconds). Vary the slope of the volcano (lava moves faster on steep slopes). Can you predict what eruption conditions are needed to reach a specific location on your map?
Compare you lava flows and relief map to known historic lava flows for the volcano you are interested it. The U.S. Geological Survey's Cascade Volcano Observatory provides detailed histories on each Cascade volcano. Do the flows on your map resemble any of the known historic lava flows? If they do what were the conditions during that eruption?
Not all volcanoes erupt fluid lava flows that travel far from the vent. Some volcanoes produce fluid mudflows that do travel far down the volcano. This demonstration could be easily modified to show areas that are susceptible to mudflows on a volcano.