7 December 2010

Let it snow! But maybe not on that volcano…

Posted by Jessica Ball

In honor of the snow (finally) reaching the north of Buffalo, I thought I’d write a post about volcanoes with chilly tops – i.e., ones covered in snow or glaciers. Although we tend to think of volcanoes as ‘hot’ geologic features, it’s fairly common for a volcano to be snow- or glacier-topped. More so for stratovolcanoes (like Rainier in the Cascades, or Fuji in Japan, or pretty much any volcano in Alaska), but it can happen at shield volcanoes too (such as Mauna Kea and Mauna Loa in Hawaii).

Mount St. Helens and Mount Rainier, 1981. Photo by Lyn Topinka, USGS Photo Library

But my main concern in choosing this topic was how ice and snow can cause or intensify volcanic hazards. As I’ve written before, water and volcanoes don’t mix well. A wet volcano is one that’s more likely to experience edifice-weakening hydrothermal alteration, may experience collapses due to extreme water inputs, and can produce deadly lahars if summit snow and ice melt (either because of seasonal temperature change or during an eruption). One excellent example of this occurred at Nevado del Ruiz in Columbia, where a relatively small eruption in 1985 melted snow and ice on the summit of the volcano and created devastating lahars that killed more than 23,000 people. Water also interacts explosively when it encounters magma, and meltwater from snow and ice can create phreatic or phreatomagmatic eruptions, which are quite violent.

Nevado del Ruiz, Columbia, 2010. NASA Earth Observatory.

Hydrothermal alteration – a hallmark of a ‘wet’ volcano – basically ‘rots’ rocks until they’re composed mainly of weak minerals like clay. Alteration on volcanoes makes them prone to debris collapses of all sizes, and the added weight of glaciers certainly doesn’t help. Glaciers can also erode parts of a volcanic edifice all on their own, changing the stress field within the volcano and making parts of its slopes more susceptible to failure. In addition, glaciers on a volcano can form ice dams which may contain lakes; when these dams fail, the lakes can cause lahars without any volcanic activity at all (this occurred at Mount Ruapehu in New Zeleand in 1953).

The topic of snow-covered volcanoes is being explored next week at several sessions of the AGU fall meeting in San Francisco. I may or may not be able to go, but here are a few titles that caught my eye:

  • 8:00 AM-12:20 PM, NH11B-1124. Glacier Destruction and Lahar Generation during the 2009 Eruption of Redoubt Volcano, Alaska C. F. Waythomas (Poster)
  • 8:00 AM-12:20 PM, NH11B-1130. Snow-ice-tephra-lava interactions during the 2010 Fimmvorduhals eruption J. Haklar; B. R. Edwards; M. T. Gudmundsson (Poster)
  • 8:00 AM-12:20 PM, C33C-0530. Ground penetrating radar survey of the ice-filled active crater of Mount Baker, Washington M. Park; D. H. Clark; J. Caplan-Auerbach (Poster)
  • 2:10 PM-2:25 PM, NH13C-03. Erosion and entrainment of snow and ice by pyroclastic density currents: some outstanding questions (Invited) J. S. Walder
  • 2:25 PM-2:40 PM, NH13C-04. Preparing for the next eruption in the Cascades: Unexpected outcomes from the 2004 – 2008 eruption of Mount St. Helens, Washington (Invited) S. P. Schilling

Because I’m preparing for the upcoming AGU meeting, I don’t have time to go as in detail as I’d like with this post, but if you’re interested in reading more about the topic of snow- and glacier-capped volcanoes, here are a few great sources: