1Four layers
The Earth has four layers: the rocky crust, the mantle, the liquid outer core and the solid inner core.
crustmantleouter coreinner core
Lesson 26.1 notes
The Earth
The layers of the Earth, how we know about them, and what the crust is made of.
2A thin skin
If the Earth were an apple, the crust would be about as thin as its skin. The crust is 5 to 70 km thick; the Earth is about 12,700 km across.
3Hotter and hotter
The deeper you go, the hotter it gets and the greater the pressure. The centre is over 5,000 °C, about as hot as the surface of the Sun.
4The mantle flows
The mantle is solid rock, but it is so hot that it flows very slowly. These slow currents move the plates of the crust a few centimetres a year.
plates
5An iron core
The core is mostly iron and nickel. Liquid iron moving in the outer core makes the Earth's magnetic field, which turns a compass needle.
ironnickel
6Rocks and minerals
The crust is made of rocks, and rocks are mixtures of minerals: natural solids with their own chemical make-up, usually compounds, like the quartz in granite.
mineral
7What the crust is made of
Almost half the crust's mass is oxygen, joined to other elements in minerals. Next come silicon, aluminium and iron.
oxygensilicon
Explore: Journey to the centre
Slide a probe from the surface to the centre of the Earth. Watch the temperature and pressure rise, and see which layer you are in.
Common mistake: The mantle is not a sea of lava
The mantle is mostly solid rock. It is so hot that it can flow very slowly, a few centimetres a year. Only small pockets near the top of the mantle melt to make magma.
Remember
- The Earth has four layers: a thin rocky crust, the mantle (hot rock that flows slowly), the liquid outer core and the solid inner core.
- The core is mostly iron and nickel. Liquid iron moving in the outer core makes the Earth's magnetic field.
- The crust is mostly oxygen and silicon, then aluminium and iron. Rocks are mixtures of minerals.
Going further at GCSE