The correct option is (b).
Explanation
The interior of the Earth is divided into three main concentric layers based on chemical composition and physical properties: the Crust, the Mantle, and the Core. These layers vary significantly in thickness, density, and composition.
Statement-wise Analysis:
- Statement 1 is Incorrect.
The crust is the thinnest layer of the Earth, constituting less than 1% of the Earth's volume. Its thickness ranges from roughly 5 km to 70 km. In contrast, the mantle is the thickest layer by volume (approximately 84%) and mass (approximately 67%), extending to a depth of 2,900 km. - Statement 2 is Correct.
The oceanic crust is significantly thinner than the continental crust. The mean thickness of the oceanic crust is approximately 5 km, whereas the continental crust has a mean thickness of around 30 km, reaching up to 70 km in major mountain systems like the Himalayas. - Statement 3 is Incorrect.
The mantle extends from the Mohorovicic discontinuity (the base of the crust) to a depth of 2,900 km (the Gutenberg discontinuity). The depth of 100 km generally corresponds to the approximate thickness of the Lithosphere (which includes the crust and the uppermost solid mantle), not the full extent of the mantle.
Key Takeaway:
The Crust is the outermost and thinnest layer (5–70 km), with oceanic crust being thinner and denser than continental crust. The Mantle is the most voluminous layer, extending from the base of the crust down to the Core-Mantle boundary at 2,900 km.