The tiny Juan de Fuca plate is largely responsible for the volcanoes that dot the Pacific Northwest of the United States. The plates make up Earth's outer shell, called the lithosphere.

which all encircle the large Pacific Plate. The plates are constantly sliding past, colliding into, or moving above or below each other. This movement results in deep ocean trenches, volcanic ...

indicating upward fluid migration from sources along the subducting Pacific plate. The fluid-rich zones in the crust seem to coincide with some of the strike-slip faults of the region. Wannamaker ...