The
Snake River Plain began to form 17 million years ago after a meteor impact in what is now southeast Oregon. A weak spot in the crust and mantle formed and created a rhyolitic volcano. As the continental crust drifted to the south west the stationary hot spot, known as the Yellowstone Hotspot, it created new volcanoes. These volcanoes formed a wide swath of flat ground, eating through mountain ranges with violent eruptions. Today the hotspot lies under the geologically active Yellowstone area.
Your post #219 reminded me of a TV program, I saw a few months ago, about all the volcanic activity and this hotspot that you speak of, lying under the whole of the geologically active Yellowstone area...it was really quite scarey to watch this program, with the experts surmising what may happen to that area in the future....its truly a place to watch...