It descends 500 miles below the town of Wisdom, Montana. travels an inch a year to the northeast, and possibly reaches all the way to the Earth’s core.
It’s tilted because the Earth’s mantle is moving. Like smoke in the wind, the hot material is caught in an eastward mantle “breeze” that moves two inches a year.
Yellowstone blows about every 650,000 years. There’s been three giant eruptions – two million years, 1.3 million and 640,000 years ago – plus many eruptions much bigger than Mount St. Helens. The next event would bury much of the West in ash.
Interview: Professor Robert Smith at NPR.
Abstract: “Geodynamics of the Yellowstone hotspot and mantle plume: Seismic and GPS imaging, kinematics, and mantle flow”