The discontinuity separating the Earth's mantle from the core is located at a depth of:

The correct option is It is located at a depth of 2,900 km..

Explanation

The interior of the Earth is differentiated into concentric layers-crust, mantle, and core-based on chemical composition and physical properties. These layers are separated by distinct boundaries called discontinuities, where seismic wave velocities change abruptly due to variations in density and material state.

Detailed Analysis:

• Depth of 2,900 km (Correct): The discontinuity separating the mantle from the core is known as the Gutenberg Discontinuity (or the Core-Mantle Boundary). It is located at a depth of approximately 2,900 km. At this boundary, the density increases sharply, and seismic S-waves stop propagating, indicating the transition from the solid lower mantle to the liquid outer core.
• Depth of 200 km: This depth lies within the asthenosphere, a semi-molten layer in the upper mantle responsible for plate tectonic movements.
• Depth of 400 km: This depth corresponds to a transition zone within the mantle where mineral phase changes occur (e.g., olivine to wadsleyite), but it does not separate the mantle from the core.
• Depth of 6,378 km: This figure represents the approximate equatorial radius of the Earth, marking the center of the planet rather than an internal boundary.

Key Takeaway: The Gutenberg Discontinuity is the boundary located at 2,900 km depth that separates the solid silicate mantle from the liquid metallic outer core.