Asthenosphere From Wikipedia, the free encyclopedia Jump to navigationJump to search The asthenosphere shown at a subduction boundary The asthenosphere (from Greek ἀσθενής asthenḗs 'weak' + "sphere") is the highly viscous, mechanically weak[1] and ductile region of the upper mantle of the Earth. It lies below the lithosphere, at depths between approximately 80 and 200 km (50 and 120 miles) below the surface. The lithosphere–asthenosphere boundary is usually referred to as LAB.[2][3] The asthenosphere is almost solid, although some of its regions could be molten (e.g., below mid-ocean ridges). The lower boundary of the asthenosphere is not well defined. The thickness of the asthenosphere dep…
