The Changing World

Structure of the Earth

The Earth’s Structure

Bristol

New York

Barcelona

If you start on the Earth’s surface how far down would you go if you travelled the same distance as the distance between London and:

Paris

Bristol = 200 km

New York = 5586 km

Barcelona = 1183 km

The distance from London to:

Paris = 343 km

Structure of the Earth

• Deepest mines in the world = 3 500 m• Deepest geological survey = 12 000 m• The Earth is 12 800 000 m in diameter

– 1000 x deeper than our deepest hole• The Earth is made of many layers• Formed millions of years ago

– Heavy matter sank to middle– Lighter matter floated on top

The Earth’s Structure

Beneath the atmosphere the Earth consists of 3 main layers:

The core

The temperature is high and the outer core is molten.. Towards the centre high pressure makes the inner core solid..

Intense heat is generated in the inner core by decay of radioactive elements like uranium.

5500 C

1110 km

3000 km

1300 km

Outer coreInner core

The core extends to about half the radius of the Earth.

It is made mostly from iron and nickel and is where the Earth’s magnetic field comes from.

It is very dense.

• How many parts make up the Earths core? What are they?

• Challenge: Why is the hotter part of the core solid, while the cooler part is liquid?

The mantle

The mantle extends outwards from the core to the crust: a distance of about 2,900 km.

It is mostly a semi-molten liquid upon which the Earth’s crust floats.

The heat coming from the core generates convection currents in the viscous mantle that cause the crust above to move.

Mantle

2900km

• What is the layer of our planet surrounding the core called?

• Challenge: This layer is not a liquid, but is often described as ‘syrupy’. Why is this?

The crust

The crust is the thin layer of rock at the surface upon which we live. Eight elements make up over 98% of the Earth’s Crust – although they are virtually entirely in the form of compounds.

Crust

20-60 km

05

101520253035404550

O Si Al Fe Ca Na K Mg

%

• What is the outer layer of the Earth known as?

• Challenge: Why do scientists think that the core is made of much denser material than the crust?

How do we know?

• By studying earthquakes– Seismic waves travel through the Earth

• The way the waves travel tells us what they’re travelling through

• Features on the surface– Cooling of the crust – cracking– Actually movement of plates

Layer Crust Mantle Core

Location Outer surface of planet

Below the crust

Centre of the planet

Thickness 6 km (ocean)35 km (land)

3000 km below surface

3500 km radius

Description ‘Skin’ of the planet

Behaves like a solid, is actually slow flowing liquid

Nickel and Iron, outer is liquid, centre is solid

• I am dense, very hot, made mostly of solid iron and nickel.

• I’m iron and nickel too, but I’m liquid.

• I’m really very thin and am mostly silicon, oxygen and aluminium

• I’m a viscous semi-solid with convection currents circulating in me.

• I just hang around on the outside. Atmosphere

Outer core

Crust

Mantle

Inner core

What am I?

Atmosphere

Outer core

Crust

Mantle

Inner core

Attach labels to the correct part of the diagram.