| More likely in Yellowstone than a
large explosive caldera-forming eruption is eruption of a lava flow, which
would be far less devastating. Since Yellowstone’s last caldera-forming
eruption 640,000 years ago, about 30 eruptions of rhyolitic lava flows have
nearly filled the Yellowstone Caldera. Other flows of rhyolite and basalt (a
more fluid variety of lava) also have been extruded outside the caldera.
Each day, visitors to the park drive and hike across the lavas that fill the
caldera, most of which were erupted since 160,000 years ago, some as
recently as about 70,000 years ago. These extensive rhyolite lavas are very
large and thick, and some cover as much as 130 square miles (340 km2),
twice the area of Washington, D.C. During eruption, these flows oozed slowly
over the surface, moving at most a few hundred feet per day for several
months to several years, destroying everything in their paths.
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Text from the United States Geological Survey website.
Yellowstone Net is
Produced by
Bruce Gourley,
Russ Finley,
&
Tim Gourley. © 1997-2007 Bruce Gourley |
