Correct Option
The correct option is A-3, B-1, C-4, D-2
Explanation
The internal structure of the Earth is stratified into three main concentric layers based on chemical composition and physical characteristics: the Crust, the Mantle, and the Core. Each layer possesses distinct properties regarding thickness, depth, and mineral composition (SIAL, SIMA, NIFE).
Statement-wise Analysis
- A. Crust - 3. Thinnest layer: The crust is the outermost solid part of the Earth and is brittle in nature. It is the thinnest layer, with a thickness ranging from approximately 5 km under the oceans (Oceanic Crust) to 30 km under the continents (Continental Crust), reaching up to 70 km under major mountain systems like the Himalayas.
- B. Mantle - 1. Extends up to 2900 km depth: The mantle lies beneath the crust, separated by the Mohorovicic (Moho) discontinuity. It extends from the base of the crust down to a depth of 2,900 km. This layer contains the asthenosphere, which is the primary source of magma.
- C. Core - 4. Made of nickel and iron: The core is the innermost layer, beginning at a depth of 2,900 km (Gutenberg discontinuity). It is composed of very heavy materials, primarily Nickel and Iron, leading to the acronym NIFE. It has the highest density among the layers.
- D. SIAL - 2. Silica and Alumina: The characteristic "Silica and Alumina" describes the composition of the continental crust. This layer is historically referred to as SIAL (Si - Silica, Al - Alumina). In contrast, the oceanic crust is referred to as SIMA (Silica and Magnesium).
Key Takeaway
The Earth's interior is organized by density: the Crust is the thinnest and lightest (SIAL/SIMA), the Mantle extends to 2,900 km, and the Core is the densest layer composed of Nickel and Iron (NIFE).