Mohorovicic discontinuity

Seismic discontinuity, marked by a rapid increase in the speed of earthquake waves, that is taken to represent the boundary between the Earth's crust and mantle. It follows the variations in the thickness of the crust and is found approximately 35–40 km/22–25 mi below the continents and about 10 km/6 mi below the oceans. It is named after the Croatian geophysicist Andrija Mohorovicic, who suspected its presence after analysing seismic waves from the Kulpa Valley earthquake in 1909. The ‘Moho’ is as deep as 70 km/45 mi beneath high mountain ranges.