Surface plates of earth are made of

Options

A. Crust and solid part of upper mantle
B. Outer heterogeneous part of crust
C. Both outer heterogeneous and lower homogeneous crust.
D. Lower homogeneous part of crust

Answer

**Step-by-Step Solution:**

1. **Understanding Earth's Structure**: The Earth is composed of several layers, including the crust, mantle, outer core, and inner core. The surface plates we refer to are primarily located in the outermost layer.

2. **Identifying the Surface Plates**: The surface plates of the Earth are known as tectonic plates. These plates float on the semi-fluid layer beneath them, which is called the asthenosphere.

3. **Composition of the Surface Plates**: The surface plates are made up of two main components:
- The **crust**, which is the outermost layer of the Earth.
- The **solid part of the upper mantle**, which lies just below the crust.

4. **Evaluating the Options**:
- **Option A**: Crust and solid part of upper mantle - This is correct as it includes both the crust and the solid upper mantle.
- **Option B**: Outer heterogeneous part of a crust - This is incomplete as it does not mention the mantle.
- **Option C**: Both outer heterogeneous and the lower homogeneous crust - This is incorrect as it includes the lower crust, which is not part of the surface plates.
- **Option D**: Lower homogeneous part of the crust - This is incorrect as the surface plates do not include the lower crust.

5. **Conclusion**: Based on the evaluation of the options, the correct answer is **Option A**, which states that the surface plates of the Earth are made up of the crust and the solid part of the upper mantle.

**Final Answer**: A) Crust and solid part of upper mantle.

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