 Adams is made of several overlapping cones that together form an 18-mile (29 km) diameter base which is elongated in its north-south axis and covers an area of 250 square miles (650 km2). The volcano has a volume of 85 cubic miles (350 km3) placing it second only to Mount Shasta in that category among the Cascade stratovolcanoes. Mount Adams was created by the subduction of the Juan de Fuca plate, which is located just off the coast of the Pacific Northwest.
