The belt of volcanoes bordering the Pacific Ocean is often called the “Circle of Fire” or the “Ring of Fire.” Earth’s crust is composed of 15 pieces, called plates, which “float” on the partially molten layer below them. Most volcanoes, earthquakes, and mountain-building occur along the unstable plate boundaries. The Circle of Fire marks the boundary between the plate underlying the Pacific Ocean and the surrounding plates. It runs up the west coast of the Americas from Chile to Alaska (through the Andes Mountains, Central America, Mexico, California, the Cascade Mountains, and the Aleutian Islands) then down the east coast of Asia from Siberia to New Zealand (through Kamchatka, the Kurile Islands, Japan, the Philippines, Celebes, New Guinea, the Solomon Islands, New Caledonia, and New Zealand). Of the 850 active volcanoes in the world, over 75 percent of them are part of the Circle of Fire.