Earth's tectonic plates (in blue) with areas (in red) of the most earthquake activity. The Earth's surface is divided up into several major plates. These are rocky slabs that float and move on the more fluid layer beneath them. The boundaries between plates are geologically active areas, where the majority of the world's volcanoes and earthquakes occur. This map shows, in red dots, the approximate areas on earth of the most earthquakes. About 90% of the world's earthquakes and 81% of the world's largest earthquakes occur along the Pacific 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.