UNDERSTANDING THE EARTH'S LITHOSPHERE AND PLATE TECTONICS The lithosphere is the solid, outermost shell of the Earth, consisting of the crust and the upper part of the mantle. It varies in thickness, about 50 km beneath the oceans and 70 to100 km beneath continents. This rigid layer is not continuous, it’s broken into tectonic plates that float atop the asthenosphere, a hot, semi-fluid layer of the upper mantle. These tectonic plates move, and their interactions are responsible for earthquakes,

The solid outermost shell of the Earth is called the lithosphere. It includes the crust and the upper, solid part of the mantle. On average, the lithosphere is about 50 kilometers thick beneath the oceans and 70 to 100 kilometers thick under the continents. The continental lithosphere and the oceanic lithosphere differ in composition and behavior. The continental crust floats on the asthenosphere, the viscous upper part of the mantle that lies beneath the lithosphere. The movement of the lithosp