I was talking about the Yellowstone series of eruptions with students the other day. Along those lines, this news item from Michael Reilly is interesting:

If you thought the geysers and overblown threat of a supervolcanic eruption in Yellowstone National Park were dramatic, you ain't seen nothing: deep beneath Earth's surface, the hot spot that feeds the park has torn an entire tectonic plate in half.

It’s the Juan de Fuca plate. The Yellowstone hotspot was highly active across the Early and Middle Miocene, the current seismic mapping study concludes that the interaction of the hotspot and subduction zone in the Pacific Northwest may have caused some unusual activity.