The asthenosphere is the layer of Earth that lies at a depth 60–150 mi (100–250 km) beneath Earth's surface. It was first named in 1914 by the British geologist J. Barrell, who divided Earth's overall structure into three...

The asthenosphere (from an invented Greek ἀσθενός a + ''sthenos "without strength") is the region of the Earth between 100 and 200 km below the surface — but perhaps extending as deep as 400 km — that is the weak or "soft" zone in...