Mohorovičić discontinuity, the seismic discontinuity that separates the Earth’s crust and mantle. Situated 25 to 40 km below the continents, 5 to 8 km below the ocean floor, and 50 to 60 km below certain mountain ranges. Characterized by a fairly abrupt increase of P-wave velocity from 6.5–7.2 to 7.8–8.5 km/s, an increase of S-wave velocity from 3.7–3.8 to 4.8 km/s, and an increase in density from approximately 2.9– 3.3 g/cm3. Continental Moho is probably different from oceanic Moho. The Moho is not the asthenosphere boundary. The Moho head wave is designated Pn. See Figure E-1. Named for Andrija Mohorovičić (1847–1936), Croatian seismologist.