Greater Pacific Northwest—Three Types of Plate Boundaries and a Hotspot

The Yellowstone Hotspot track is superimposed on other tectonic provinces of the Pacific Northwest. The hotspot first surfaced 17 million years ago as massive outpourings of fluid basalt lava in the Columbia Plateau and Steens Basalt region. Surfacing of the hotspot was affected by subduction that is now manifest as the Cascadia Subduction Zone where the Juan de Fuca Plate descends beneath the edge of the continent. Since then the North American Plate has been moving west-southwest over the hotspot, so that a chain of explosive rhyolite volcanic centers (pink blobs) extends across the Snake River Plain to Yellowstone. This line of supervolcanoes is concurrent with continental rifting forming the Basin and Range Province.