Moho zone separates the crust and mantle. It is one of the discontinuity layers in the earth's interior. It is defined by the distinct change in velocity of seismological waves as they pass through changing densities of rock. It is 5 to 10km below the ocean floor, and 20 to 90km beneath typical continental crusts, with an average of 35km. This layer has been named after Andrija Mohorovicic.