The Mohorovičić discontinuity or the Moho

The Mohorovičić discontinuity, or simply the Moho, is the transitional boundary between the crust of the Earth and the underlying mantle located 5-10 km (3-6 mi) beneath the ocean floor and 20-90 km (10-60 mi) beneath the surface of continents. The Moho marks a transition from the basaltic rocks of the crust above it to the denser peridotitic and dunitic rocks below it. Also notably, seismic waves travelling through the Moho suddenly accelerate . Reaching the Moho has been high on the wish lists of geologists, geophysicists, and seismologists for many decades, but the difficulty of reaching such depths is immense. The most notable attempt to drill down to the Moho was the Soviet Union’s Kola Superdeep Borehole, and while it never quite reached the discontinuity, it did reveal plenty of secrets about the deeper portions of the Earth’s crust.