Map of the Pacific, showing the 'Ring of Fire,' which follows the contours of the tectonic plates (in red). About 90% of the world's earthquakes and 81% of the world's largest earthquakes occur along the Ring of Fire, which is also home to over 75% of the world's active and dormant volcanoes. This intense seismic and volcanic activity is caused by the movement of tectonic plates in the Earth's crust under the ocean moving against those under the land.