. The Earth's lithosphere is broken into numerous plates. They move in the directions shown by the arrows at rates of a few tenths of a meter per year. The lithosphere dives into the underlying asthenosphere at zones of subduction. They are denoted by the thick line with triangles, forming the famous ring of fire around the edge of the Pacific and Nazca Plates. Most of the Earth's earthquake and continental volcanic activity is concentrated along the subduction zones.
Copyright 2010, Professor Kenneth R. Lang, Tufts University