The earth consists of four layers, the crust, mantle, outer core and inner core. The crust is the outermost layer, which is made of rock (Basalts and Granite). Under the continents the crust is around twenty-five miles thick and under the ocean it is three to five miles thick (five to forty km). The crust is much thinner than any of the other layers, and is made of calcium, sodium and aluminum. Being sort of cold, the crust is rocky and brittle so it can fracture very easily in earthquakes. The lithosphere or the crust and the upper part of the mantle are cool and rigid. Next you reach the mantle. The asthenosphere is hot, partially melted and very slow flowing, and is located at the upper part of the mantle. The mantle flows consistency of asphalt. The mantle (the thickest of the layers) is eighteen hundred miles thick (two thousand eight hundred and eighty-five km). Next you reach the outer core, which is fourteen hundred miles thick (twenty-two hundred mile thick). The outer core is made of iron and nickel in the liquid state. The inner core consists of iron and nickel in the solid state. The inner core is around eight hundred mile thick (one thousand two hundred and sixteen km). The core is mostly iron and is so hot that the outer core is molted, with about 10% sulfur. The inner core is under so much pressure that is solid. Most of the Earth’s mass is in the mantle, which is made of iron, magnesium, aluminum, silicon, and oxygen.