The North American Plate off the coast is bounded by four tectonic plates to thw est (Gorda, Juan de Fuca, Pacific, and Explorer. The plates boundaries are defined by the Cascadia Subduction Zone, the Gorda, Juan de Fuca and Explorer mid-mid ocean ridge spreading centers, and a series of transform faults (also known as fracture zones. Environments closer to shore include the shelf, slope and abyssal plain. A seamount chain marks the movement of the Pacific Plate over a "hot spot" on the Juan de Fuca Ridge, and includes the Cobb Seamount guyot. Credit: D. Kelley, University of Washington.