Lithosphere: from the Greek lithos (stone, rock) and sphaira (sphere). It is the Earth’s rigid and hard outer layer capable of generating earthquakes. It includes the Earth’s crust and the upper portion of the mantle down to a less rigid and more fluid layer called the asthenosphere, which is easily deformable and therefore does not produce earthquakes. The total thickness of the lithosphere varies from about 70–75 km beneath ocean basins to 110–113 km beneath continents. The lithosphere is further divided into the oceanic lithosphere, associated with the oceanic crust and about 100–150 km thick, and the continental lithosphere, associated with the continental crust, with thickness ranging from 40 to 200 km. The lithosphere is fragmented into a series of tectonic plates, along whose boundaries geological phenomena such as magmatism, volcanism, orogeny, and seismic activity occur.
