The earth has four layers :the crust, mantle,inner core and outercore. The lithosphere is the crust and the upper part of a mantle. The lithosphere is a about 5 to 30 miles deep.the mantle is about 1800 miles thick. The outercore is about 1300 miles thick and the inner core is about 800 miles to the center of earth. The inner core is a solid layer.Earthquakes start at the lithosphere. The crust is a thin rocky skin. The thinnest part of a crust is under the ocean. The ocean floor is heavy, dense rock and the land is lighter, lense dense rock. The upper part of mantle is cooler than the deep mantle. The deep mantle is very hot because it rides on top of the extremely hot outer core and therefore it causes the mantle and crust to slowly move .The mantle is made of manny different rocky materials