Moho

The Moho, or Mohorovičić discontinuity, is the boundary that separates Earth's crust from the underlying mantle. It is identified by a sudden increase in seismic wave speed, indicating a change in rock composition. Think of it as the "layer switch," marking the crust's end and the mantle's beginning. This boundary varies in depth—from about 5 to 70 kilometers beneath the surface—being shallow under ocean floors and deeper under continents. The Moho is essential for understanding Earth's internal structure, seismic activity, and the processes that shape our planet.