"...what is the evidence for repeated super-volcnaos"? - blanknoone
The underlying "Yellowstone" structure began with a comet strike that punctured the upper and lower crust of the earth, causing lava flows that formed the Columbia River Plateau - in Washington State! Later, as the upper crust moved towards the Pacific, the punctured lower crust again allowed massive flows, forming the Snake River Plain - in Idaho. Now, Yellowstone, in Wyoming, has moved over that same weakened lower crust; it's blown in a big way there three times, so far. Repetition enough?
Got a link? That would be a good read.