Learn at a Glance: Layers of Earth

The Earth is made of several layers, one inside another, each with different materials and properties. Understanding these layers helps us know why earthquakes and volcanoes happen, where minerals come from, and how the surface we live on is supported. Read the sections below to learn about the structure of the Earth simply and clearly.

What are the main layers of the Earth?

The Earth has three main layers arranged like the layers of an onion. These are the crust, the mantle, and the core. Each layer differs in composition, thickness and temperature.

1. The Crust

• The crust is the outermost thin layer where we live. It contains soil, rocks, mountains and the oceans.
• There are two types of crust: continental crust (under continents) and oceanic crust (under the oceans).
• The continental crust is thicker (about 30-70 km) and made mainly of lighter rocks such as granite.
• The oceanic crust is thinner (about 5-10 km) and made mainly of denser rocks such as basalt.
• The crust is broken into large pieces called tectonic plates. The movement of these plates causes earthquakes and forms mountains.

2. The Mantle

• The mantle lies below the crust and is the thickest layer of the Earth, extending to a depth of about 2,900 km.
• The mantle is made of hot, solid rock that can slowly flow like very thick syrup; parts of it are partially molten.
• Heat inside the mantle causes convection currents. These currents slowly move the tectonic plates on the crust.
• The uppermost part of the mantle together with the crust forms the lithosphere, a rigid layer that makes up tectonic plates.
• Just below the lithosphere is the asthenosphere, a weaker and slightly softer layer that allows plates to move.

3. The Core

• The core is at the centre of the Earth and is made mainly of iron and nickel.
• The core has two parts: the outer core and the inner core.
• The outer core is liquid and lies beneath the mantle; its movement helps create the Earth's magnetic field.
• The inner core is solid because the pressure there is extremely high, even though temperatures are very hot.
• The temperature increases with depth and can reach several thousand degrees Celsius in the core.

Diagram of the Earth's layers

How do scientists know about the layers?

• Scientists study how earthquake waves (seismic waves) travel through the Earth. Different layers change the speed and direction of these waves.
• Some waves cannot pass through liquids; using this, scientists discovered the outer core is liquid while the inner core is solid.
• Studies of volcanic rocks and meteorites also give clues about the materials that make up the Earth.

Why the layers matter - examples and everyday effects

• Movement of the mantle (convection currents) causes tectonic plates to move, which leads to earthquakes, volcanoes and the formation of mountains.
• The crust supplies soil and rocks used for building and farming, and holds mineral resources like coal, iron, copper and gemstones.
• The Earth's magnetic field, produced by the outer core, protects living things from harmful solar radiation.

Key terms

• Crust - the thin, outermost layer of the Earth where life exists.
• Mantle - the thick layer of hot rock below the crust; it moves slowly and drives plate motion.
• Core - the central part of the Earth made mainly of iron and nickel; includes outer (liquid) and inner (solid) core.
• Lithosphere - the rigid outer shell made of crust plus the uppermost mantle; it forms tectonic plates.
• Asthenosphere - the softer layer of the upper mantle below the lithosphere that allows plate movement.
• Seismic waves - vibrations produced by earthquakes; used by scientists to study Earth's interior.