The Earth's structure

This lesson covers: 

1. The Earth’s layers
2. The properties of the crust, mantle and core
3. How the crust consists of moving tectonic plates

The Earth's internal structure

The Earth can be divided into distinct layers. It has:

1. A thin, solid outer layer called the crust.
2. An inner layer known as the mantle.
3. A dense central region called the core.

The crust

• The crust is the outermost layer of the Earth.
• It is made up of solid rock and is relatively thin compared to the other layers.
• Life exists on top of the crust, as it provides a surface for plants, animals and humans to live on.

The mantle

• The mantle lies between the crust and core, and makes up the largest section of the Earth.
• It is made up of very hot, slowly flowing rock that acts a bit like a liquid.
• The rock is able to flow as the temperature and pressure increases deeper into the mantle.

The core

• At the centre of the Earth lies the core, the Earth's innermost layer.
• Scientists believe the core is composed chiefly of iron and nickel.
• It is much hotter than the overlying mantle due to immense pressure.

Tectonic plates

The crust and upper mantle are divided into rigid pieces called tectonic plates:

• Tectonic plates are huge slab-like segments of the crust and upper mantle.
• They fit together like pieces of a jigsaw puzzle, with oceans and continents atop them.
• Plates slowly move across the mantle in different directions, at speeds of a few centimetres a year.
• Their motion can cause earthquakes and volcanic activity at plate boundaries.