Question

The Mohorovicic Discontinuity separates which two layers of the Earth?

• A. Crust and Mantle
• B. Mantle and Outer Core
• C. Outer Core and Inner Core
• D. Lithosphere and Asthenosphere

Hint:

Important Earth interior discontinuities:

• \textbf{Mohorovičić Discontinuity (Moho)} $\rightarrow$ Crust and Mantle
• \textbf{Gutenberg Discontinuity} $\rightarrow$ Mantle and Outer Core
• \textbf{Lehmann Discontinuity} $\rightarrow$ Outer Core and Inner Core

Remember: \textbf{Moho = Crust–Mantle boundary}.

Answer 1

The Correct Option is A

Concept: The interior of the Earth is divided into several layers based on their composition and physical properties. The three major layers of the Earth are:

• Crust
• Mantle
• Core

Between these layers, there exist boundaries known as discontinuities, where the properties of seismic waves change abruptly. These discontinuities help scientists understand the structure of the Earth's interior. One of the most important boundaries is the Mohorovičić Discontinuity, commonly called the Moho. It marks the boundary between the Earth's crust and the mantle.
Step 1: Understanding the Mohorovičić Discontinuity.
The Mohorovičić Discontinuity was discovered in 1909 by the Croatian seismologist Andrija Mohorovičić. He observed that seismic waves from earthquakes suddenly increased in speed at a certain depth inside the Earth. This change in velocity indicated that the waves had entered a different layer of the Earth with different physical properties.
Step 2: Location of the Moho boundary.
The Moho lies at different depths depending on the region:

• About 5–10 km below the oceanic crust
• About 30–50 km below the continental crust

At this boundary, seismic waves travel faster because mantle rocks are denser and more rigid than crustal rocks.
Step 3: Evaluating the options.

• Crust and Mantle: Separated by the Mohorovičić Discontinuity. (Correct)
• Mantle and Outer Core: Separated by the Gutenberg Discontinuity.
• Outer Core and Inner Core: Separated by the Lehmann Discontinuity.
• Lithosphere and Asthenosphere: Separated by a mechanical boundary within the upper mantle, not the Moho.

Thus, the Mohorovičić Discontinuity separates the: \[ \text{Crust and Mantle} \]