https://phys.org/news/2018-07-yellowstone-super-volcano-history-previously-thought.html

"In this research, there was no evidence of heat coming directly up from the Earth's core to power the surface volcano at Yellowstone," Zhou said. "Instead, the underground images we captured suggest that Yellowstone volcanoes were produced by a gigantic ancient oceanic plate that dove under the Western United States about 30 million years ago. This ancient oceanic plate broke into pieces, resulting in perturbations of unusual rocks in the mantle which led to volcanic eruptions in the past 16 million years."

The eruptions were very explosive, Zhou added. A theoretical seismologist, Zhou created X-ray-like images of the Earth's deep interior from USArray—part of the Earthscope project funded by the National Science Foundation—and discovered an anomalous underground structure at a depth of about 250 to 400 miles right beneath the line of volcanoes.