The boundary in the Earth’s interior between the crust and the upper mantle, marking a change in rock density from 3.3 (crust) to 4.7 (mantle). Clague and Straley (1977) Geology 5, 3 see the oceanic Moho as the boundary separating partially serpentinized ultramafic rocks, above, and fresh tectonized ultramafic rocks below.

The Moho occurs at about 35 km below the continents (but can be depressed to nearly 50 km depth; see Fuis et al. (2008) Geology 36, 3), and at around 10 km beneath the oceans.