The Lithosphere is the outermost layer of the Earth. The lithosphere is divided into two parts namely the crust and the uppermost part of the mantle.
Our planet has an outer solid, rocky layer which has all its plates moving on top of it continuously. They are called tectonic plates. They are located under the lithosphere and rest upon it.
Earth’s lithosphere, which constitutes the hard and rigid outer vertical layer of the Earth, includes the crust and the uppermost mantle.
The lithosphere is underlain by the asthenosphere which is the weaker, hotter, and deeper part of the upper mantle.
The Lithosphere-Asthenosphere boundary is defined by a difference in response to stress: the lithosphere remains rigid for very long periods of geologic time in which it deforms elastically and through brittle failure, while the asthenosphere deforms viscously and accommodates strain through plastic deformation.
The thickness of the lithosphere is thus considered to be the depth to the isotherm associated with the transition between brittle and viscous behavior.
The temperature at which olivine becomes ductile (~1000 °C) is often used to set this isotherm because olivine is generally the weakest mineral in the upper mantle.
The lithosphere is subdivided horizontally into tectonic plates, which often include terranes accreted from other plates.
