Article
Article
Asthenosphere
Article By:
Rawlinson, Nick Research School of Earth Sciences, Australian National University, Canberra, Australia.
Last reviewed:October 2019
DOI:https://doi.org/10.1036/1097-8542.056750
A layer of variable thickness within the upper mantle of the Earth that is mechanically weaker (less rigid) than both the overlying lithosphere and the underlying mesosphere. The depth of transition from lithosphere to asthenosphere can be as little as 20 km (12 mi) in oceanic settings and as great as 250 km (155 mi) in continental settings. In both cases, the asthenosphere may extend in depth to over 300 km (186 mi) [Fig. 1]. The presence of a mechanically weak layer in the upper mantle can be attributed to the temperature and pressure conditions being such that the ratio between the temperature of mantle material and its melting point (solidus) is a maximum. See also: Earth's interior; Lithosphere
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