Structure of Earth

Key Stage 3

The structure of Earth is what the Earth is made from, underneath the surface.


A diagram showing the layers of the Earth.

Crust: The top layer of the Earth is called the Crust. It is made of rocks but two thirds is covered in a layer of water.
Mantle: The layer under the Crust is called the Mantle. It is made of rock that is under such a high pressure that it behaves plastically.
Outer Core: The Outer Core is a liquid layer below the Mantle.
Inner Core: Underneath the Outer Core is the Inner Core at the very centre of Earth. It is a solid sphere.

The structure of Earth is what the Earth is made from, underneath the surface.

The structure of Earth has been discovered by observing seismic waves.

Both P-waves and S-waves are refracted as they move through the Earth which gives information about the density underneath the surface of Earth.

S-waves do not travel through liquids, as they are absorbed, so this can show where there is liquid underneath the surface of Earth.

	This diagram shows the path of seismic waves through the Earth. P-waves are refracted gradually as they pass deeper into the Earth because the rock becomes more dense the deeper down. P-waves are refracted at the interface between the Mantle and the Outer Core. This causes some P-waves to change direction and results in a 'shadow zone' between 100° and 145°, from their source, where P-waves do not reach seismic detectors. S-waves do not pass through liquids and are not detected beyond 100° from their source. This shows that the core of the Earth must be a liquid.

Crust: The top layer of the Earth is called the Crust. It is made of rocks but two thirds is covered in a layer of water.
Mantle: The layer under the Crust is called the Mantle. It is made of rock that is under such a high pressure that it behaves plastically.
Outer Core: The Outer Core is a liquid layer below the Mantle.
Inner Core: Underneath the Outer Core is the Inner Core at the very centre of Earth. It is a solid sphere.