Relax. These supervolcanoes aren't active today, but 30 million years ago more than 5,500 cubic kilometers of magma erupted during a one-week period near a place called Wah Wah Springs.
By comparison, this eruption was about 5,000 times larger than the 1980 Mount St. Helens eruption.
Dinosaurs were already extinct during this time period, but what many people don't know is that 25-30 million years ago, North America was home to rhinos, camels, tortoises and even palm trees. Evidence of the ancient flora and fauna was preserved by volcanic deposits.
Scientists used radiometric dating, X-ray fluorescence spectrometry, and chemical analysis of the minerals to verify that the volcanic ash was all from the same ancient super-eruption.
They found that the Wah Wah Springs eruption buried a vast region extending from central Utah to central Nevada and from Fillmore on the north to Cedar City on the south. They even found traces of ash as far away as Nebraska.
But this wasn't an isolated event; the Brigham Young University geologists found evidence of fifteen super-eruptions and twenty large calderas.
Supervolcanoes are different from the more familiar stratovolcanoes -- like Mount St. Helens -- because they aren't as obvious to the naked eye and they affect enormous areas. They don't stand as high cones. At the heart of a supervolcano instead, is a large collapse.
Those collapses in supervolcanoes occur with the eruption and form enormous holes in the ground in plateaus, known as calderas.
Not many people know that there are still active supervolcanoes today. Yellowstone National Park in Wyoming is home to one roughly the same size as the Wah Wah Springs caldera, which was about 25 miles across and 3 miles deep when it first formed.
Source - http://www.sciencedaily.com/releases/2013/12/131211093945.htm
Four minute video by Bingham Young University scientist
and more info on the subject
http://news.byu.edu/archive13-dec-supervolcano.aspx
More volcano items on this blog - http://ottersandsciencenews.blogspot.ca/search/label/Volcanoes
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