Movements within this layer of semi-solid material drive the movement of the crustal plates. a. Lithosphere b. Lower mantle c. Asthenosphere d. Moho
The correct answer and explanation is :
The correct answer is:
c. Asthenosphere
Explanation:
The asthenosphere is a crucial layer of the Earth’s interior that plays a significant role in the movement of tectonic plates. It is a semi-solid, ductile region of the upper mantle located beneath the lithosphere, typically extending from about 100 km to 250 km below Earth’s surface. The asthenosphere is composed of partially molten rock, making it mechanically weaker and more deformable than the rigid lithosphere above it.
How Does the Asthenosphere Drive Plate Movement?
- Convection Currents:
- The asthenosphere is heated by the intense temperatures from the Earth’s core. This heat causes convection currents—hot material rises towards the surface, cools down, and then sinks back.
- These circulating currents generate a slow but continuous movement, which acts as a conveyor belt for the lithospheric plates resting above.
- Plasticity and Flow:
- Unlike the rigid lithosphere, the asthenosphere has plasticity, meaning it can flow very slowly over long periods.
- This allows the rigid plates of the lithosphere to slide, pull apart, or collide, leading to plate tectonics.
- Effects on Earth’s Surface:
- Movement within the asthenosphere is responsible for major geological activities, including earthquakes, volcanic eruptions, and mountain formation.
- It also contributes to seafloor spreading at mid-ocean ridges and subduction at deep ocean trenches.
Why Not the Other Options?
- Lithosphere (a): Rigid, not responsible for plate movement.
- Lower Mantle (b): Too deep and solid, not directly involved.
- Moho (d): A boundary, not a layer that moves plates.
Thus, the asthenosphere is the driving force behind the movement of crustal plates.