1. Mohorovičić discontinuity (Moho): This is the boundary between the Earth's crust and the upper mantle. It is characterized by a sudden increase in seismic wave velocity, indicating a change in rock composition and density.
2. Gutenberg discontinuity: This boundary separates the mantle from the Earth's outer core. It is marked by a sharp decrease in seismic wave velocity, indicating a transition from solid rock to liquid iron and nickel.
3. Lehmann discontinuity: This marks the boundary between the Earth's outer core and its solid inner core. Seismic wave velocities increase again at this boundary, suggesting the transition from liquid to solid iron and nickel.
While some resources may mention only two discontinuities, the Lehmann discontinuity is also crucial for understanding Earth's structure and the behavior of seismic waves within it.
