Correct Option
The correct option is (c) 1 and 3 only.
Explanation
The interior of the Earth is divided into three main layers: the crust, the mantle, and the core. The core is the innermost layer, distinguished by its high density, metallic composition, and extreme physical conditions.
Statement-wise Analysis
- Statement 1 is Correct: The core is the innermost layer of the Earth. It has a radius of approximately 3,500 km. It is separated from the mantle by the Gutenberg Discontinuity.
- Statement 2 is Incorrect: The core is primarily composed of heavy metals, specifically nickel and iron, and is often referred to as the nife layer. Silica and magnesium (sima) are the primary constituents of the oceanic crust, not the core.
- Statement 3 is Correct: The central core experiences extreme physical conditions. It is characterized by very high temperature and pressure due to the weight of the overlying layers and the radioactive decay of elements.
Key Takeaway: The Earth's core is the innermost layer (radius ~3,500 km), composed mainly of Nickel and Iron (nife), whereas Silica and Magnesium (sima) characterize the oceanic crust.