Subduction of the "Juan de Fuca" under the pacific northwest is responsible for the "cascade" volcanoes.
The Cascade Volcanoes are various volcanoes in a volcanic circular segment in western North America, reaching out from southwestern British Columbia through Washington and Oregon to Northern California, a separation of well more than 700 miles (1,100 km).
The Cascade Volcanoes were framed by the subduction of the Juan de Fuca, Explorer and the Gorda Plate (leftovers of the a lot bigger Farallon Plate) under the North American Plate along the Cascadia subduction zone. This is a 680-mile (1,090 km) long blame, running 50 miles (80 km) off the shore of the Pacific Northwest from northern California to Vancouver Island, British Columbia. The plates move at an overall rate of over 0.4 inches (10 mm) every year at a to some degree slanted point to the subduction zone.