“What goes up must come down”

Volcanoes are exceptional in the fact that they grow. Each time they erupt lavas or tephras, they build themselves taller and wider. These volcanic materials are often loose or heavily fractured. Consequently, the higher the volcano grows, the more unstable they become. To put it simply: what goes up must come down.

Mt St Helens before (left) and after (right) the 1980 eruption and associated collapse (Harry Glicken, USGS)

Elevation model of Mt. St Helens before (top) and after (bottom) the 1980 eruption and associated collapse (USGS, http://pubs.usgs.gov/circular/c1050/century.htm)

When they do come down, the landslide is so large and so fast that the results can be catastrophic. In the past 400 years, it is estimated that 20,000 people have died in these events (Siebert, 1987).

The frequency of these events in volcanic settings and the potential for devastation makes volcanic collapse a ‘Big Idea‘ in volcanology. By understanding collapses, we can understand more about volcanic processes and be better able to reduce the risks for humans who live near volcanoes.An excellent and newly published overview of volcanic collapses and their hazards can be found here.

We can discuss this phenomena in the following sub-topics:

9.1  Volcanic collapse is a common evolution of volcanoes

9.2  Collapses come in many forms

9.3  Volcanoes are inherently unstable

9.4  Volcanic collapses can produce many hazards

9.5  Volcanic landslides are larger and more devastating than non-volcanic collapses

9.6  Volcanic collapses leave evidence

9.7  The causes of any given collapse are different and poorly understood

9.8  Every volcano can collapse

9.9  Our understanding of volcanic collapse is improving all the time, but they are still difficult to predict

Comments are open on each page. Please feel free to discuss any of the topics, or come up with one of your own! Make sure to browse the misconceptions on the topic and people who are involved in current and past research. References on each page are cited in full here.