The correct option is 1 and 3 only.
Explanation
The internal structure of the Earth is divided into three concentric layers based on chemical and physical properties: the crust, the mantle, and the core. These layers are separated by distinct discontinuities.
Statement 1 is Correct:
The crust is the outermost solid part of the Earth. It is brittle in nature. Its thickness varies significantly, being thinner under the oceans (approximately 5 km) and thicker under the continents (approximately 30 km), reaching up to 70 km in major mountain systems.
Statement 2 is Incorrect:
The mantle extends from Moho’s discontinuity (the boundary between the crust and the mantle) to a depth of 2,900 km. The statement incorrectly limits the depth to 500 km. While the upper portion of the mantle (asthenosphere) extends up to roughly 400 km, the mantle as a whole continues much deeper to the Gutenberg discontinuity (core-mantle boundary).
Statement 3 is Correct:
The core is the innermost layer, extending from 2,900 km to the centre of the Earth (approximately 6,370 km). It is composed of very heavy material, primarily constituted by nickel and iron, and is often referred to as the NIFE layer.
Key Takeaway:
The Earth's mantle extends from the Moho discontinuity to a depth of 2,900 km, whereas the core is a dense layer composed chiefly of Nickel and Iron (NIFE).