Understanding Isostatic Compensation

Isostatic compensation refers to the geological principle where the Earth's crust "floats" on the denser, semi-fluid mantle at an elevation dependent on its thickness and density. It's a state of gravitational equilibrium.

Elevated Land Mass Adjustments

An elevated land mass experiences adjustments based on its state of compensation:

• Over-Compensation: This implies the land mass is elevated more than expected for its density, suggesting excess buoyancy. This excess buoyancy drives further uplift to regain equilibrium.
• Otherwise (Standard or Under-Compensation): In scenarios that are not over-compensated, the land mass either sits at a standard elevation or is less elevated than its density would suggest. If additional mass is added, or if adjustment requires lowering, it undergoes subsidence.

Conclusion on Compensation

Therefore, an elevated land mass attaining isostatic compensation behaves as follows:

• It is uplifted when in a state of over-compensation (excess buoyancy).
• It undergoes subsidence otherwise (standard or under-compensated states requiring adjustment downwards).

This corresponds to option C.