The odds of a catastrophic eruption at Yellowstone are 1 in 730,000 or 0.00014% (better than the lottery).

http://pubs.usgs.gov/fs/2005/3024/

Although it is possible, scientists are not convinced that there will ever be another catastrophic eruption at Yellowstone. Given Yellowstone's past history, the yearly probability of another caldera—forming eruption could be calculated as 1 in 730,000 or 0.00014%. However, this number is based simply on averaging the two intervals between the three major past eruptions at Yellowstone — this is hardly enough to make a critical judgement. This probability is roughly similar to that of a large (1 kilometer) asteroid hitting the Earth. Moreover, catastrophic geologic events are neither regular nor predictable.

http://volcanoes.usgs.gov/yvo/2005/docudrama.html


>Terry, I thought that the whole Las Palmas issue was revised to be a very unlikely occurence. As to to the mega-caldera in Yellowstone, there would have to be a lot of signs a long time before that happened and there are few, if any, signs that anything is happening there.
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>If you want to look at potential surprises, the New Madrid fault in the US Mid-West could provide one. Could annihilate Memphis or any number of Mississippi cities.
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>Gamma ray bursts, asteroids....anything can happen.
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>>>http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2008/04/14/BAGC104TGE.DTL&feed=rss.bayarea
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>>When half of Las Palmas slides into the sea, causing a tsunami that'll engulf the whole eastern seaboard, the Yellowstone Park mega caldera erupts (due any day now), etc. I don't think you'll need worry about a mere earthquake.