The last time the Yellowstone Caldera acted up was 640,000 years ago, not a million. It's blown about every 600,000 years, so it's overdue. Craters of the Moon National Monument and Preserve was created by vulcanism about 2,000 year back and the area was, at that time, inhabited by the ancestors of the modern Shoshone; the event is noted in Shoshone history.