Question

What does the concept of isostasy primarily describe?

• A. Hydrostatic equilibrium of the Earth's crust floating on a denser substrate
• B. Movement of tectonic plates due to convection
• C. Formation of mountains due to compression
• D. Cooling of the Earth's mantle

Hint:

Remember: \[ \boxed{ \text{Isostasy} = \text{Floating equilibrium of the lithosphere on the asthenosphere} } \] It explains crustal uplift and subsidence due to loading and unloading.

Answer 1

The Correct Option is A

Concept: Isostasy is the state of gravitational equilibrium in which the Earth's lithosphere floats on the denser and more plastic asthenosphere. It is analogous to an iceberg floating on water.

Step 1: Understand isostatic equilibrium. The Earth's crust adjusts vertically so that the pressure at a certain depth remains nearly equal. When additional load is added or removed,
• Mountains sink under added load.
• Uplift occurs after erosion or melting of glaciers.

Step 2: Identify the correct description. Thus, \[ \boxed{\text{Isostasy describes the hydrostatic equilibrium of the Earth's crust floating on a denser substrate}.} \] Therefore, the correct option is \[ \boxed{(A).} \]