Lithosphere

A lithosphere (from Ancient Greek λίθος (líthos) 'rocky' and σφαίρα (sphaíra) 'sphere') is the rigid,[1] outermost rocky shell of a terrestrial planet or natural satellite.

[citation needed] The thickness of the lithosphere is thus considered to be the depth to the isotherm associated with the transition between brittle and viscous behavior.

[citation needed] The concept of the lithosphere as Earth's strong outer layer was described by the English mathematician A. E. H. Love in his 1911 monograph "Some problems of Geodynamics" and further developed by the American geologist Joseph Barrell, who wrote a series of papers about the concept and introduced the term "lithosphere".

These ideas were expanded by the Canadian geologist Reginald Aldworth Daly in 1940 with his seminal work "Strength and Structure of the Earth.

These concepts of a strong lithosphere resting on a weak asthenosphere are essential to the theory of plate tectonics.

The thickness of the mantle part of the oceanic lithosphere can be approximated as a thermal boundary layer that thickens as the square root of time.

The age is often equal to L/V, where L is the distance from the spreading centre of mid-ocean ridge, and V is velocity of the lithospheric plate.

New oceanic lithosphere is constantly being produced at mid-ocean ridges and is recycled back to the mantle at subduction zones.

[15][16] Yet others stick down into the mantle as far as 400 kilometres (250 mi) but remain "attached" to the continental plate above,[13] similar to the extent of the old concept of "tectosphere" revisited by Jordan in 1988.

[17] Subducting lithosphere remains rigid (as demonstrated by deep earthquakes along Wadati–Benioff zone) to a depth of about 600 kilometres (370 mi).

The crust is distinguished from the upper mantle by the change in chemical composition that takes place at the Moho discontinuity.

[22] The upper part of the lithosphere is a large habitat for microorganisms, with some found more than 4.8 km (3 mi) below Earth's surface.