Friday, November 9, 2007

Spotlight on the Yellowstone Super Volcano

Yellowstone National Park sits on top of 3 collapsed volcanic magma chambers or calderas. This geologic hotspot has been formed by some of the most powerful volcanic explosions in geologic history. The last major eruption, about 640,000 years ago, released 1,000 cubic kilometers of material, covering all of North America in up to two meters of debris. By comparison, Mount St. Helen's released 1.2 cubic kilometers of ejecta in 1980.

Recent activity, geologically speaking has included non-explosive eruptions of lava flows about 70,000 years ago, small steam explosions 13,000 years ago which formed the Mary Bay crater and the formation of Craters of the Moon National Monument between 11,000 and 2,000 years ago.

The magma chamber beneath the caldera's surface contains dissolved gases which are kept under pressure of magma and the overburden material. A geologic shift, such as an earthquake, could release some of the gasses causing the magma to expand. As the magma expands, more gasses are released and a chain reaction ensues. The rapid expansion may cause the crust to blow resulting in very large gas explosion.
Geologist are continually monitoring the movement of the ground. The maximum measured ground uplift over the past 36 months is about 17 cm. Yellow stone has experienced about 819 earthquakes in the past year.

Tune in to NPR's Talk of the Nation today for a discussion with Jacob B. Lowenstern, Ph.D. from the USGS.


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