Asthenosphere

Highly viscous, ductile, and mechanically weak region of Earth's mantle

The asthenosphere (from Ancient Greek ἀσθενός (asthenós) 'without strength') is the mechanically weak and ductile region of the upper mantle of Earth. It lies below the lithosphere, at a depth between c. 80 and 200 km (50 and 120 mi) below the surface, and extends as deep as 700 km (430 mi).

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