2/2/09

We exist on a thin crust of solid rock which overlies the churning cauldron of Earth's interior.  When molten rock extrudes onto the surface, we call it a volcano, and these can take a huge variety of forms.  Today I will focus on three volcanoes which have shown recent signs of life:  one which may be about to blow, one which is probably not going to go off any time soon but could cause a global disaster when it does, and one which has been recently and intermittently active, causing an entire town to make the painful decision to relocate.

The Redoubt Volcano is showing alarming signs of activity, and volcanolgists are warning that there could be a large eruption any day now!  This volcano is only 100 miles southwest of Anchorage. When it erupted 20 years ago it shot a plume of ash 40,000 feet into the air.  A passenger jet approaching Anchorage sucked in enough ash to shut the engines down.  The  cloud of ash also etched the windshield glass so severly that the pilots could barely see.  Some skillful flying averted disaster.  Now the volcano is rumbling to life again and people in Anchorage are stocking up on emergency supplies. Seismic activity has been far above normal background levels, and small vapor plumes have been observed, but as of this writing (6 PM Mountain 2/2/09) there has been no eruption.

The Alaska Volcano Observatory site is a good place to stay abreast of seismic measurements, maps, webcams and warnings.

A much more devestating, and fortunately much more unlikely event would be the eruption of the Yellowstone supervolcano.  Yellowstone park in Wyoming is not only a beautiful wonderland of geysers and hot springs.  It lies above an ancient hot spot in the Earth where molten mantle rock rises near the surface, forming one of the largest supervolcanos in the world.  Several times in the past fantastically violent eruptions have buried the western part of North America in ash.   The last full scale eruption was 640,000 years ago.  You wouldn't have wanted to be anywhere in Wyoming or any of the neighboring states when this occurred.  It blasted about 240 cubic miles of rock and ash into the air!  If this happened today it would not only devastate thousands of square miles in the Western U.S. but it could also cause a climate disaster as the ash and dust  traveled around the globe on the winds, blocking sunlight and cooling the surface for a few years - long enough to seriously disrupt several growing seasons.   Although such an eruption is unlikely any time soon, knowing what I know about what has happened there in the past and probably will again someday, it did get my attention when I saw, this last December, that a new swarm of hundreds of small Earthquakes was being reported.  As magma rises in a chamber below the ground, it often causes such earthquake swarms.  This kind of activity at Yellowstone is not that unusual, but the swarm in December and early January was unusually large, consisting of over 800 earthquakes. This was the second largest of these swarms ever observed.  It strikes me that when "the big one" does come to Yellowstone, the early signs may be similar to what occurred there late last year!

The United States Geological Survey maintains a map of current earthquake activity at Yellowstone here.  When I saw the swarm in December I did e-mail a friend who lives in those parts and say "Dude, I hope you have your supervolcano insurance paid up!".  But things have quieted down and chances are he is safe for another several hundred thousand years.  And of course all that ash ultimately adds nutrients to the soil, so after it wipes out forests and agriculture for hundreds of miles in every direction, it will eventually help new things to grow.  Apreciating geology does require a certain level of detachment, or at least taking a very long view of things that can seem a little nihlistic...

And meanwhile in Chile, the Chaiten Volcano, which erupted in May, 2008 after staying dormant for 9000 years, continues to spew steam and ash.  Check out these fantastic satellite images on the NASA Earth Observatory site.  Recently the Chilean government announced that they would relocate the entire town of Chaiten, which was largely buried by the eruption last year.  Life in a subduction zone, where one of Earth's tectonic plates dives beneath another causing frequent volcanic eruptions, as along the West Coast of South America, is often not easy.

Some related news links:

Redoubt Volcano:

http://www.sciam.com/blog/60-second-science/post.cfm?id=life-on-the-ring-of-fire-earthquake-2009-01-30

http://www.cnn.com/2009/TECH/science/01/30/alaska.volcano/

http://www.google.com/hostednews/ap/article/ALeqM5hcWJaxwgurm_TV9AVcObQBWbS25QD961D1MO0

Yellowstone earthquake swarm:

http://www.denverpost.com/news/ci_11610449

Chaitén Volcano:

http://www.patagoniatimes.cl/index.php/20090129736/News/Health-Sience/CHILES-CHAITEN-TO-BE-RELOCATED.html