The lithosphere, or the solid, outer part of Earth, is about 44 to 62 miles thick. It is 3,958 miles to the center of the Earth. Flowing rocks and molten minerals are a relatively short distance below the surface of oceans and landmasses.
The lithosphere includes the crust and the solid, uppermost mantle of the Earth. The rigid lithosphere floats on the non-rigid, warmer, partly liquid layer just beneath it, the asthenosphere. There, temperatures can reach 1,832 degrees Fahrenheit, rocks may flow and about 10 percent of the material is molten. Scientists believe the asthenosphere is in constant motion, causing earthquakes, volcanoes and continental drift.