The Cascade Volcanoes were formed by the subduction of the Juan de Fuca, Explorer and the Gorda Plate (remnants of the much larger Farallon Plate) under the North American Plate along the Cascadia subduction zone. This is a long fault, running off the coast of the Pacific Northwest from northern California to Vancouver Island, British Columbia. The plates move at a relative rate of over 0.4 inches (10 mm) per year at a somewhat oblique angle to the subduction zone.