Science Olympiad Dynamic Planet Practice Test

Which part of the mantle is involved in tectonic movement and isostatic adjustments?

1. Upper mantle

2. Asthenosphere

3. Lower mantle

4. Transition zone

The correct answer is: Asthenosphere

The asthenosphere is a region of the upper mantle that is crucial for tectonic movement and isostatic adjustments. It lies beneath the lithosphere (which includes the crust and the uppermost part of the mantle) and is characterized by its semi-fluid, malleable nature due to partial melting and high temperatures. This semi-fluid state allows the tectonic plates of the lithosphere to move over it. Tectonic movement involves the shifting of Earth's plates, driven by convection currents in the more fluid parts of the mantle. The asthenosphere is particularly important in this process, as its properties facilitate the movement of these plates. Isostatic adjustments occur when the weight of the overlying material, such as ice or sediment, changes. The asthenosphere responds to these changes, allowing the lithosphere to rise or sink to achieve a balance, a process known as isostasy. Therefore, the asthenosphere plays a critical role in both tectonic activity and the buoyancy of the lithosphere.