���˿���

• The Earth has a layered structure made up of the core, the mantle and the crust.
• Different elements are present in different parts of the Earth’s structure.
• The crust is made from enormous plates which move very slowly due to movements of the mantle below.

The Earth is a planet and is roughly the shape of a sphere. There are three layers that make up the Earth’s structure.

The three layers, starting from the outside, are:

• the crust – the rocky outer layer
• the mantle – the semi-solid middle layer
• the core - the innermost layer which is divided into an inner core and outer core

The Earth and its atmosphere are the only sources of elements for use in everyday life.

Human activities use a wide range of elements, including:

• hydrogen (H) and oxygen (O) found in water
• iron (Fe) used for building materials and in car bodies

These elements can be found in the crust, the atmosphere and the oceans, which all form part of the Earth’s structure.

The crust is made of huge pieces of land called tectonic plates which fit together like a huge jigsaw. These plates move around because they are floating on the semi-solid mantle below them, and this moves very slowly. The tectonic plates only move a few centimetres each year.

In this diagram, the red lines represent the edges of the tectonic plates that make up the Earth's crust.

Tectonic plates are rocky and contain many elements.

Oxygen

Oxygen is the element that makes up the largest percentage of the crust. It is found in a variety of compounds, bonded to metal and non-metal elements. These compounds are called minerals and they make up different types of rocks.

Silicon

The second most common element is silicon, found as silicon dioxide in sand and rocks. Silicon is a very useful element used for semi-conductors in electronics as well as in glass and pottery.

Other elements

There are also significant amounts of aluminium, iron and calcium. These are all important metals used in manufacturing.

The crust is mined for the elements and compounds it contains. However, the resources on Earth are finite, meaning they will run out if not used in a sustainable way.

For example, iron is mined from the Earth's crust in quarries. It is a finite resource meaning it will eventually run out. This could take hundreds of years or be much quicker depending on how humans use resources.

The mantle is a semi-solid layer below the crust. There are no elements in this part of the Earth's structure that can be easily extracted.

The mantle is the thickest layer of the Earth and is made of semi-solid rock that moves very slowly, like a liquid. The tectonic plates float on top of the mantle, meaning the tectonic plates and the mantle move at the same time.

The core is made of iron, with a smaller amount of nickel. The inner core is solid and the outer core is liquid. Humans do not extract elements from the Earth's core.

The two metals in the core, iron and nickel, are both magnetic. This is what gives the Earth its magnetic field, including the north and south poles.

Did you know?

The movement of magnetic metals in the core causes the poles to move slightly each year. 780,000 years ago, the poles were completely opposite to what they are now.

Test your knowledge of the Earth's different layers in this quiz.

The structure of the Earth has been debated for many centuries and ideas on how the Earth is structured have changed over time.

• In the late 1500s, the Brabantian (now Belgium) cartographer Abraham Ortelius noticed that coastlines of some countries looked like they might fit together.

• Just over 300 years later, in 1912, the German geologist Alfred Wegener proposed a theory called continental drift. This was a was a revolutionary theory suggesting that continents shift position on the Earth's surface.
• Wegener also proposed that all the continents were once part of a super continent called Pangaea. Wegener could not correctly explain what caused the continents to move but his ideas eventually led to modern theories of plate tectonics.
• In modern times, equipment like seismometers (which measure earthquakes) have been used to give evidence about the Earth’s structure. Scientists now agree on the theory of plate tectonics.