<P> The Mohorovičić discontinuity (Croatian pronunciation: (moxorôʋiːt͡ʃit͡ɕ)), usually referred to as the Moho, is the boundary between the Earth's crust and the mantle . Named after the pioneering Croatian seismologist Andrija Mohorovičić, the Moho separates both the oceanic crust and continental crust from underlying mantle . The Moho lies almost entirely within the lithosphere; only beneath mid-ocean ridges does it define the lithosphere--asthenosphere boundary . The Mohorovičić discontinuity was first identified in 1909 by Mohorovičić, when he observed that seismograms from shallow - focus earthquakes had two sets of P - waves and S - waves, one that followed a direct path near the Earth's surface and the other refracted by a high - velocity medium . </P> <P> The Mohorovičić discontinuity is 5 to 10 kilometres (3--6 mi) below the ocean floor, and 20 to 90 kilometres (10--60 mi) beneath typical continental crusts, with an average of 35 kilometres (22 mi). </P>

The boundary that separates the crust from the mantle is the