Surface plates of earth are able to move with respect to one another because

Options

A. The lie over semi-molten asthenosphere
B. Centrifugal force generated due to spinning of earth
C. Orbital movement of earth
D. Gravitational pull of Sun and Moon.

Answer

To solve the question "Surface plates of earth are able to move with respect to one another because," we will analyze the options provided and arrive at the correct answer step by step.

### Step-by-Step Solution:

1. **Understanding Earth's Layers**: The Earth's structure is divided into several layers. The two most relevant layers for this question are the lithosphere and the asthenosphere.
- **Lithosphere**: This is the outer layer of the Earth, which is hard and consists of the crust and upper mantle. It is relatively thin compared to the layers below it.
- **Asthenosphere**: Located beneath the lithosphere, the asthenosphere is semi-molten and behaves like a viscous fluid. This layer is crucial for the movement of tectonic plates.

2. **Identifying the Movement of Plates**: The question asks why the surface plates (tectonic plates) can move relative to one another. The movement is primarily due to the underlying layer they rest upon.
- The lithosphere (the tectonic plates) floats on the asthenosphere, which is in a semi-molten state. This semi-fluid nature allows the lithosphere to move.

3. **Evaluating the Options**:
- **Option A**: They lie over semi-molten asthenosphere. (This is correct as explained above.)
- **Option B**: Centrifugal force generated due to spinning of Earth. (This does not directly cause the movement of tectonic plates.)
- **Option C**: Orbital movement of Earth. (This is not related to the movement of tectonic plates.)
- **Option D**: Due to gravitational pull of sun and moon. (While this affects tides, it does not directly cause tectonic plate movement.)

4. **Conclusion**: The correct answer is **Option A**: "They lie over semi-molten asthenosphere." This explains the reason for the movement of tectonic plates.

### Final Answer:
The surface plates of Earth are able to move with respect to one another because they lie over the semi-molten asthenosphere.

---