What is the Moho?

The Moho is the Mohorovicic Discontinuity. A seismic discontinuity is a boundary between 2 layers with different properties. The Mohorovicic discontinuity (Moho) is the crust - mantle boundary (within the lithosphere) representing a sudden compositional change (e.g. gabbro changes to peridotite at the oceanic Moho).