The Mohorovičić iscontinuity, usually referred to as the Moho, is the boundary between the Earth's crust and the mantle. The Moho serves to separate both oceanic crust and continental crust from underlying mantle. The Moho mostly lies entirely within the lithosphere; only beneath mid-ocean ridges does the Moho also define the lithosphere-asthenosphere boundary. The Mohorovičić discontinuity was first identified in 1909 by Andrija Mohorovičić, a Croatian seismologist, when he observed the abrupt increase in the velocity of earthquake waves (specifically P-waves) at this point. Ophiolites are sections of oceanic crust and possible mantle rock that have been obducted into the continental crust during plate collisions.