The Lehmann discontinuity forms boundary between :

Question

Accepted Answer

The Lehmann discontinuity marks a significant change in seismic wave velocities within the Earth's interior. This boundary is specifically located within the Earth's core. The Earth's core is divided into two distinct layers: the solid inner core and the liquid outer core. The Lehmann discontinuity is the boundary that separates these two layers. Seismic waves, particularly P-waves, exhibit a noticeable increase in velocity as they pass from the liquid outer core into the solid inner core. This velocity change is what defines the Lehmann discontinuity.

Now, let's examine why the other options are incorrect:

*   **Option 1: Crust and Mantle:** The boundary between the crust and the mantle is known as the Mohorovičić discontinuity (often shortened to Moho). The Lehmann discontinuity is much deeper within the Earth.

*   **Option 2: Mantle and Core:** The boundary between the mantle and the core is known as the Gutenberg discontinuity. This is a major boundary where seismic waves are significantly refracted and slowed down. The Lehmann discontinuity is located within the core itself, not at its boundary with the mantle.

*   **Option 3: Inner Mantle and Outer Mantle:** While the mantle does have compositional and physical variations, there isn't a universally recognized "inner mantle" and "outer mantle" division with a distinct discontinuity named after Lehmann. The Lehmann discontinuity is specifically associated with the core.