Lithosphere

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Earth cutaway
The tectonic plates of the lithosphere.

The lithosphere[1] is the solid shell of the planet Earth. That means the crust and the part of the upper mantle that behaves elastically on time scales of thousands of years or greater.

Under the lithosphere there is the asthenosphere, the weaker, hotter, and deeper part of the upper mantle. This part can flow.

The lithosphere provides a conductive lid atop the convecting mantle; as such, it affects heat transport through the Earth.

Types of lithosphere[change | change source]

There are two types of lithosphere:

  1. Oceanic lithosphere, which is associated with oceanic crust and exists in the ocean basins. Oceanic lithosphere is typically about 50–100 km thick
  2. Continental lithosphere, which is associated with continental crust. Continental lithosphere has a range in thickness from about 40 km to perhaps 200 km, of which about 40 km is crust.

The lithosphere is divided into tectonic plates, which move gradually relative to one another.

Oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge. This thickening occurs by conductive cooling, which converts hot asthenosphere into lithospheric mantle, and causes the oceanic lithosphere to become increasingly dense with age. Oceanic lithosphere is less dense than asthenosphere for a few tens of millions of years, but after this becomes increasingly denser than asthenosphere.

When a continental plate comes together with an oceanic plate, at a subduction zones, the oceanic lithosphere always sinks beneath the continental.

New oceanic lithosphere is constantly being produced at mid-ocean ridges and is recycled back to the mantle at subduction zones. As a result, oceanic lithosphere is much younger than continental lithosphere: the oldest oceanic lithosphere is about 200 million years old, while parts of the continental lithosphere are billions of years old.

Another distinguishing characteristic of the lithosphere is its flow properties. Under the influence of the low-intensity, long-term stresses that drive tectonic motion, the lithosphere responds essentially as a rigid shell and thus deforms primarily through brittle failure, whereas the asthenosphere (the layer of the mantle below the lithosphere) is heat-softened and accommodates strain through plastic deformation.

Relevant pages[change | change source]

Other websites[change | change source]

Other sources[change | change source]

  • Earth's Crust, Lithosphere and Asthenosphere
  • Crust and Lithosphere
  • Barrell, J. 1914a The strength of the Earth's crust. Journal of Geology.22, 425-433.
  • Barrell, J. 1914b The strength of the Earth's crust. Journal of Geology 22, 441-468.
  • Barrell, J. 1914c The strength of the Earth's crust. Journal of Geology 22, 655-683.
  • Daly, R. 1940 Strength and structure of the Earth. New York: Prentice-Hall.
  • Stanley Chernicoff and Donna Whitney. Geology. An Introduction to Physical Geology, 4th ed., Pearson 2007

References[change | change source]

  1. IPA: lith'usfēr, from the Greek for "rocky" sphere