12-28-2008, 08:23 PM
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Old broad
Join Date: Oct 2002
Location: Away
Posts: 13,933
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Quote:
Originally Posted by StuBradley
I don't know exactly how 'above normal' that is but there were only two earthquakes in the park the week previous to this spurt of activity. Hoping someone here can provide some further info.
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Quote:
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Yellowstone experiences thousands of small earthquakes every year, virtually all of which are undetectable to people. There have been six earthquakes with at least magnitude 6 or greater in historical times, including a 7.5 magnitude quake that struck just outside the northwest boundary of the park in 1959. This quake triggered a huge landslide, which caused a partial dam collapse on Hebgen Lake; immediately downstream, the sediment from the landslide dammed the river and created a new lake, known as Earthquake Lake. Twenty-eight people were killed, and property damage was extensive in the immediate region. The earthquake caused some geysers in the northwestern section of the park to erupt, large cracks in the ground formed and emitted steam, and some hot springs' normally clear water turned muddy.[29] A 6.1 magnitude earthquake struck inside the park on June 30, 1975, but damage was minimal. For three months in 1985, 3,000 minor earthquakes were detected in the northwestern section of the park, during what has been referred to as an earthquake swarm, and has been attributed to minor subsidence of the Yellowstone caldera.[32] Beginning on April 30, 2007, sixteen small earthquakes with magnitudes up to 2.7 occurred in the Yellowstone Caldera for several days. These swarms of earthquakes are common, and there have been 70 such swarms between 1983 and 2006.[44] Seismic activity in Yellowstone National Park continues and is reported hourly by the Earthquake Hazards Program of the U.S. Geological Survey.[45]
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http://en.wikipedia.org/wiki/Yellowstone |
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