Moho

The Moho, or Mohorovicic discontinuity, is the seismic boundary between the crust and the mantle, marked by a sharp rise in P-wave velocity from about 6.8 to 8.0 km/s. Andrija Mohorovicic identified it in 1909 from a 1909 Croatian earthquake whose waves split into two travel-time branches. It lies about 7 km below the seafloor under oceanic crust and roughly 35 km below the surface under typical continental crust, deepening to 50 to 70 km beneath mountain belts. The Moho separates low-density crustal rock from the denser peridotite of the upper mantle and anchors crustal-thickness estimates in marine seismic work.