[jpsb]

"The underlying "Yellowstone" structure began with a comet strike that punctured the upper and lower crust of the earth"

Got a link? That would be a good read.

[mdefranc]

I haven't searched for online geology texts. A non-technical paperback that details catastophic earth events, including Yellowstone, is "Agents of Chaos" by Stephen L. Harris, 1990, Mountain View Press. It explains how plate tectonics drive earthquakes and volcanoes, studying in detail various geological disasters in the American West.