Which one of the following is found in the innermost part of the Earth

Which one of the following is found in the innermost part of the Earth ?

Conrad discontinuity
Moho discontinuity
Guttenberg discontinuity
Lehmann discontinuity
This question was previously asked in
UPSC NDA-1 – 2023
The correct answer is D) Lehmann discontinuity.
The Earth is structured in layers: crust, mantle, outer core, and inner core. Discontinuities are boundaries where seismic waves change speed due to changes in material properties. The Lehmann discontinuity is located at a depth of approximately 5150 km and separates the liquid outer core from the solid inner core. Since the inner core is the innermost part of the Earth, the Lehmann discontinuity is found at the boundary of this innermost region.
– The Conrad discontinuity is a theoretical or regional boundary within the continental crust.
– The Moho discontinuity (Mohorovičić discontinuity) is the boundary between the Earth’s crust and the mantle (around 35-70 km under continents, 5-10 km under oceans).
– The Guttenberg discontinuity (also known as the Wiechert–Gutenberg discontinuity or Core–mantle boundary) is the boundary between the Earth’s mantle and the outer core (around 2900 km depth).