what is a asthenosphere in geology
The asthenosphere is a part of the upper mantle just below the lithosphere that is involved in plate tectonic movement and isostatic adjustments.n the old oceanic mantle the transition from the lithosphere to the asthenosphere, the so-called lithosphere-asthenosphere boundary (LAB) is shallow (about 60 km in some regions) with a sharp and large velocity drop (5-10%).