Internal Structure of the Earth
“The Earth’s internal structure consists of several concentric layers, each with unique physical and chemical properties.”
Definition
- Internal Structure of the Earth: The Earth is made up of three main layers — the Crust, Mantle, and Core — arranged in concentric shells, each differing in composition, temperature, and state of matter.
Main Layers of the Earth
- 1. Crust: The outermost solid layer; it is brittle and composed mostly of silicates.
- 2. Mantle: Lies beneath the crust; semi-solid and extends to 2,900 km depth. Composed of silicate rocks rich in iron and magnesium.
- 3. Core: Divided into the Outer Core (liquid) and Inner Core (solid). Composed mainly of iron and nickel.
Detailed Composition of Layers
| Layer |
Thickness |
Composition |
State |
| Crust |
5-70 km |
Silicon, Aluminum, Oxygen (SIAL) |
Solid |
| Mantle |
~2,900 km |
Silicon, Magnesium, Iron (SIMA) |
Semi-solid |
| Outer Core |
~2,200 km |
Iron, Nickel |
Liquid |
| Inner Core |
~1,200 km |
Iron, Nickel |
Solid |
Interesting Facts
- The inner core is as hot as the surface of the Sun (~6000°C).
- Seismic waves help us understand Earth's internal structure.
- The crust is thinnest under oceans and thickest under mountains.
- Earthquakes and volcanic eruptions are linked to mantle activity.
Previous Year Questions
- SSC CGL 2019: What is the outermost layer of Earth?
- The Crust
- RRB NTPC 2020: Which layer of the Earth is made of liquid metal?
- Outer Core
- HSSC CET 2022: Name the heaviest part of the Earth.
- Core
- SSC MTS 2018: What is the composition of the mantle?
- Silicates of iron and magnesium
- RRB Group D 2019: What causes the Earth's magnetic field?
- Movements in the liquid outer core
- SSC JE 2017: Which method is used to study Earth's interior?
- Seismic wave analysis
- HSSC JE 2019: Name the layer between the crust and core.
- Mantle
- SSC CHSL 2017: Why is the inner core solid?
- Due to immense pressure