Lava Domes

Introduction

Lava domes, which may also be referred to as volcanic domes, are common features in volcanic regions throughout the world. Lava domes can come in many shapes and sizes, and while they may not be quite as spectacular as their explosive or flowing counterparts, they are often still an awe inspiring sight to see. The purpose of this page is to provide a brief introduction to lava domes, which will by no means be entirely comprehensive. In fact, even today, there is still much unknown about lava domes and what they can potentially reveal about volcanic systems.

Lava domes are formed by viscous magma being erupted effusively onto the surface and then piling up around the vent. Like lava flows, they typically do not have enough gas or pressure to erupt explosively, although they may sometimes be preceded or followed by explosive activity. However, unlike lava flows, the lava that forms domes is often to thick and sticky to flow very far, and thus instead pile up thick and high around the vent.

 

MSH Lava Dome

 

Photo credit: USGS. 1984 USGS picture of the growing Mount St. Helens Lava dome. This lava dome started developing shortly after the iconic May, 18th 1980 eruption and dome growth continued until 1986.

 

 

 

Chillahuita

 

Photo credit: Casey Tierney.  2009 picture of Chillahuita lava dome found in the Andes Mountains of South America. Note the large difference in appearance (and size!) as compared to the 1980’s Mount St. Helens Lava dome.

 

 

 

 


 

References and Additional Resources

 

USGS website on lava domes. http://vulcan.wr.usgs.gov/Glossary/Domes/description_lava_dome.html

Francis, P., Oppenheimer, C. 2004. Volcanoes. 2nd Ed. Oxford University Press, New York.

Fink J. H., Anderson, S.W. 2000. Lava domes and Coulees, In: Sigurdsson et al., eds., Encyclopedia of Volcanoes, Academic Press, 307-319.

Blake, S., 1989, Viscoplastic models of lava domes, IAVCEI Proceddings in Volcanology, Vol.2. Lava flowsand domes, Springer Verlag, Heidelberg, 88-126.

de Silva, S.L., Self, S., Francis, P.W., Drake, R.E., Ramirez, C., 1994. Effusive silicic volcanism in the Central Andes: The Chao dacite and other young lavas of the Altiplano-Puna Volcanic Complex. Journal of Geophysical Research, 99, 17,805-17,825.

Shape and Size of Lava Domes

 

The shape and size of lava domes varies greatly, but they are typically steep-sided and thick. The thickness can range anywhere from a few meters to nearly one kilometer in height. The diameter or length of these domes can range from a few meters to many kilometers. They can take on my forms, including circular and flat-topped (Tortas), circular and spiney (Peleean), piston shaped (Upheaved Plugs), and sometimes they can even take on a hybrid form between lava flow and lava dome (Coulee) (Blake, 1999). The form that the dome takes is a function of many factors including strength and viscosity of the lava, as well as the slope of the land they are erupted onto.

 

Chao

Photo credit: Shan de Silva. 2009 picture of Chao, a very large lava dome in the Andes.

Note that the flow front you are seeing is as high as 700m in places and Chao itself is over 14km long!!

 


References

Blake, S., 1989, Viscoplastic models of lava domes, IAVCEI Proceddings in Volcanology, Vol.2. Lava flowsand domes, Springer Verlag, Heidelberg, 88-126.

de Silva, S.L., Self, S., Francis, P.W., Drake, R.E., Ramirez, C., 1994. Effusive silicic volcanism in the Central Andes: The Chao dacite and other young lavas of the Altiplano-Puna Volcanic Complex. Journal of Geophysical Research, 99, 17,805-17,825.

Where do Lava Domes Form?

 

Lava domes can form anywhere associated with volcanic activity. They are commonly found within the crater of large composite volcanoes, such as Mount St. Helens, but are not limited to this location. They also often occur on the flanks of volcanoes. Lava domes can also be completely isolated from other volcanic features, or they may also occur in chains. Ultimately what determines where a lava dome will form is the magmatic plumbing system that supplies them.

MSH Lava Domes

 

 

 

Photo credit: USGS.

The two Mount St. Helens lava domes are examples of lava domes which form in or on the flanks of large composite cones. Lava domes such as these will ultimately one day rebuild Mount St. Helens.

 

 

 

 

 

Chillahuita

 

 

 

 

 

Photo Credit: Casey Tierney.

Chillahuita is an example of an isolated lava dome which is, however , related to many other domes in the area.

 

 

 

 

 

 


References

Francis, P., Oppenheimer, C. 2004. Volcanoes. 2nd Ed. Oxford University Press, New York.

USGS. http://vulcan.wr.usgs.gov/Glossary/Domes/framework.html

How Does a Lava Dome Form?

 

Again, this varies from lava dome to lava dome. Domes can be single distinct events or they may form as the composite of many eruptions that build upon each other. They can grow by erupting on-top of previous dome material, or alternatively they can grow by filling from within; a sort of inflation.

The length of time it takes for a lava dome to form also varies greatly. Some lava domes grow in a matter of hours or day, while others may take years – some taking upwards of 100 years to reach their full extent.

The stages of development seen below, the Mount St. Helens 1980-1986 lava dome is an example of a composite lava dome that grew episodically.

MSH 198-1986 Lava Dome

MSH Lava Dome DevelopmentMSH Lava Dome Development

Photo and graphic credits: USGS. The top picture shows the 1980-1986 Mount St. Helens lava dome as it was growth. The bottom two images depict the devlopment through time of that lava dome. As you can see, it was built in many different events.


References

Francis, P., Oppenheimer, C. 2004. Volcanoes. 2nd Ed. Oxford University Press, New York

de Silva, S.L., Self, S., Francis, P.W., Drake, R.E., Ramirez, C., 1994. Effusive silicic volcanism in the Central Andes: The Chao dacite and other young lavas of the Altiplano-Puna Volcanic Complex. Journal of Geophysical Research, 99, 17,805-17,825.

USGS. http://vulcan.wr.usgs.gov/Glossary/Domes/framework.html

What Are Lava Domes Made Of?

 

The lava that forms the domes can have a very wide range of composition, anywhere from basalt to rhyolite. However, the lavas that most frequently form domes are generally lavas that are higher in Silica (SiO2) and are thus generally more viscous.  Lava domes take on a variety of textures, but are often blocky in nature.

Dacite Lava

 

 

Photo credit: Casey Tierney.

A block of dacite lava. Dacite lava can frequently be found creating lava domes due to its relatively viscous nature.

 

 

 

 

Occasionally, even obsidian (Rhyolite Glass) will be erupted and can form lava domes, such as Glass Mountain in California.

 

Obsidian

 

 

 

Photo credit: USGS.

A sample of black rhyolite glass known as Obsidian, sometimes seen forming lava domes such as Glass Mountain in California.

 

 

 

 


 

References

Francis, P., Oppenheimer, C. 2004. Volcanoes. 2nd Ed. Oxford University Press, New York.

Fink J. H., Anderson, S.W. 2000. Lava domes and Coulees, In: Sigurdsson et al., eds., Encyclopedia of Volcanoes, Academic Press, 307-319.

 

Features of Lava Domes

 

Lava domes demonstrate a large variety of textures and features, depending largely on composition and the ability of the lava dome to deform and flow. Listed below are a few of these features and breid descriptions of each.

Blocks

 

Lava domes are often seemingly just a pile of loose and sharp blocks divided by large cracks and spaces between the blocks. Indeed, due to the composition of the lavas that form the domes (typically viscous and high in silica), the lava tends to form and cool into large blocks, varying in size from less than a centimeter to well over 5m. And although blocks may appear randomly placed, their distribution probably reflects eruption dynamics (Fink and Anderson, 2000). These blocks are often unstable and form a field of talus surrounding the lava dome.

Blocks

 

 

 

Photo credit: Shan de Silva.

Large lava blocks near the edge of Chillahuita lava dome in the Andes.

 

 

 

 

 

 

 

Explosion Pits

In the distal regions of the lava dome, always from the primary vent, explosion pits are often found. These pits can be many meters deep and disrupt the surface of the lava dome. They are probably caused by high water content releasing and trapping steam beneath the surface of the lava dome. Eventually the pressure builds to high and a small explosion occurs (Fink and Anderson, 2000)

Pressure Ridges (Ogives)

Ogives are commonly found on lava flows, and often resemble the pahoehoe ropes sometimes seen on basaltic lava. These ridges can also be found on some lava domes known as coulées, sometimes found to as much as 30m high. The ridges are formed as a result of compressional forces, parallel to flow of the coulée. The outer surface of the coulée must have a viscosity that is higher than the interior but also must be able to deform in a ductile manner. The spacing and height of these features depends largely on composition.

Chao Sat

 

 

 

Chao, as seen in this satellite image, is an excellent example of a coulée. Note the large pressure ridges visible on the surface of the lava. The ridges on Chao can be over 30m high.

 

 

 

 

 

 

 

 

 

 

 

Crease Structures

Another common feature seen on lava domes and flows are crease structures. These features develop where lava is allowed to spread laterally as the outer part of the lava flow cools and lava from the interior is still plastic. The processes of creating larger cracks often occurs in multiple episodes of cooling and subsequent fracturing. Often, new extrusions of lava will emerge from these cracks. Size of the cracks can vary from less than a meter to almost 250m (Fink and Anderson, 2000)

 

Large Crease Structure

 

 

Photo credit: Shan de Silva.

Note volcanologist, Casey Tierney, for scale!  

This picture is of a large crease structure found in a lava flow in the Andes.  

 

 

 

 

 

 

 


 

References

Fink J. H., Anderson, S.W. 2000. Lava domes and Coulees, In: Sigurdsson et al., eds., Encyclopedia of Volcanoes, Academic Press, 307-319.

USGS. http://vulcan.wr.usgs.gov/Glossary/Domes/framework.html

Types of Lava Domes

 

Lava Dome Types

 

 

Lava domes can be divided based on their shape, texture and eruptive style.  For the purposes of this overview we have chosen to stick with the Blake (1999) classification of lava domes, based primarily on morphology.  See figure left.

The four major types are Low Lava Dome (or Torta), peléean, coulées, and upheaved Plug.

 

 

 

 

 

 

 

 

Tortas

Named after their striking resemblance to cake or “Torta”, these domes are common throughout the world, but especially so in the Andes mountains of South America.  This type of lava dome is generally erupted on mostly flat ground and as a result the lava is able to push outwards, but not far. They typically are flat-topped and roughly circular. The thickness and diameter of these domes can vary greatly from a few meters to nearly a kilometer in thickness and several kilometers in diameter. These domes grow by internal processes and lava fills in the center of the dome near the vent and pushes older layers outwards, forming an onion-like internal structure. 

 

 ChillahuitaChillahuita Sat.

 Photo credits: Casey Tierney (Left) and Google Maps (Right).

 Chillahuita is an excellent example of a torta. Note the steep sides and the flat top.

Peléean

Named after the iconic lava dome formed on Mt. Pelee in 1902 (which eventually collapsed resulting in the destruction of St. Pierre on Martinique), these lava domes are often the steepest sided of all lava domes. They are typically circular similar to Tortas, but rather than having a flat top, they show relatively smooth upper surfaces punctuated by tall vertical spines. These vertical spines give these domes a craggy appearance and also frequently collapse causing talus slopes to frequently surround these domes. This type of dome is most commonly found associated with larger composite volcanoes.

 

 Mount St. Helens 2004-2006 Lava Dome

 

 

 

Photo credit: USGS.

The large spine growing out of the 2004-2006 Mount St. Helens lava dome makes it an example of a Peléean lava dome.

 

 

 

 

 

 

Coulées

Coulées are a hybrid between a lava dome and a lava flow. In order to get the thick and sticky lava to flow, this type of dome is generally erupted on steep slopes which allow the lava to ooze slowly down the slope. Typically they do not flow more than a few kilometers, though some larger examples have traveled well over 10km.  As a neat feature of coulées, huge pressure ridges, known as Ogives, are often seen on the outer surface of the flow.

 

ChaoChao Sat.

Photo credit: Shan de Silva.  

Chao, located in the Andes, is an excellent example of a coulée. It was erupted on a very steep slope which allowed it to flow for nearly 14km downslope. The flow front is over 700m high. Note the distinct Ogives on the surface.

 

Upheaved Plugs

Upheaved Plugs are a rare and interesting type of lava dome. The erupting lava has a higher yield strength (thus is stronger) than the lavas that form other domes, and as a result this lava is pushed up like a piston. These piston like extrusions often travel high above the surface and sometimes carry country rock sediment along with them.

 

Upheaved Plug in Japan

 

 

 

 

Photo from Francis, P., Oppenheimer, C. 2004.

 

Shinzan dome in Japan.  Masao Momatsu recorded the stages of growth by drawing on his window overlooking the dome.

 

 

 

 

 

 

 

 

Cryptodomes

Related to lava domes is a volcanic feature known as a cryptodome. A cryptodome occurs when magma is brought very near the surface but does not breach to the surface. This shallow intrusion of magma forms a bulge on the surface, closely resembling a lava dome.

 


References

Francis, P., Oppenheimer, C. 2004. Volcanoes. 2nd Ed. Oxford University Press, New York.

Fink J. H., Anderson, S.W. 2000. Lava domes and Coulees, In: Sigurdsson et al., eds., Encyclopedia of Volcanoes, Academic Press, 307-319.

Blake, S., 1989, Viscoplastic models of lava domes, IAVCEI Proceddings in Volcanology, Vol.2. Lava flowsand domes, Springer Verlag, Heidelberg, 88-126.

de Silva, S.L., Self, S., Francis, P.W., Drake, R.E., Ramirez, C., 1994. Effusive silicic volcanism in the Central Andes: The Chao dacite and other young lavas of the Altiplano-Puna Volcanic Complex. Journal of Geophysical Research, 99, 17,805-17,825.

 

Dangers of Lava Domes

 

While one could easily outpace the eruption and growth of a lava dome, some extreme hazards do exist as the result of lava domes. When lava domes are growth rapidly and becoming unstable they will often collapse and spawn large and deadly pyroclastic density currents. In fact, pyroclastic flows due to lava dome collapse have been responsible for many of the largest volcanic disasters in history, including the 1902 destruction of St. Pierre on the island of Martinique. On May 8, 1902 the large and growing lava dome at Mount Pelée collapsed sending a large flow into the capital city of St. Pierre, killing all but two of the citizens.

This was scientists’ first experience with pyroclastic density currents, and while many lessons were learned that day, and have been learned since, people continue to be at risk from lava dome collapse spawned PDCs. Those especially at risk are scientists working near or on the volcano, and local community members whose homes could potentially be build on the flanks of an active volcano. It is imperative that we continue to try to understand lava dome dynamics so that we can better understand and work to mitigate the risk posed to people by lava dome collapse.

 


References

Francis, P., Oppenheimer, C. 2004. Volcanoes. 2nd Ed. Oxford University Press, New York.