Science
What are the layers of the Earth?
Quick answer
Earth has four main layers: a thin rocky crust, a thick mantle of hot rock, a liquid outer core and a solid inner core. Each layer is hotter than the one above it.
In one sentence
The Earth is made of four layers, the crust, mantle, outer core and inner core, and it gets hotter as you go deeper.
Explained
Imagine a boiled egg. The thin shell is like Earth's crust, the white is like the mantle and the yolk is like the core. Earth is more complicated, but the layers do work like this, one inside another.
volcano
rock
globe
- Crust: the outside layer, made of solid rock. It is thin, only about 5 to 10 kilometres under the oceans and about 30 to 50 kilometres under the continents. We live on top of it.
- Mantle: a thick layer, about 2,900 kilometres deep, of hot rock. It is solid, but over millions of years it flows very slowly, like thick putty.
- Outer core: about 2,200 kilometres thick, made of melted iron and nickel. Its movement helps create Earth's magnetic field, which makes compasses point north.
- Inner core: a ball of solid iron and nickel in the centre. It is as hot as the surface of the Sun, around 5,000 to 6,000 degrees Celsius, but the enormous pressure keeps it solid.
From the surface to the centre is about 6,371 kilometres. Nobody has been anywhere near. The deepest hole ever drilled, in Russia, goes down only about 12 kilometres. Scientists learn about the deep layers from the waves made by earthquakes, which travel differently through solid and liquid.
The crust is broken into huge pieces called plates. They float on the mantle and move a few centimetres a year, which builds mountains and causes quakes and volcanoes. You can read about this in plate tectonics.
Examples
| Layer | Thickness (about) | State |
|---|---|---|
| Crust | 5 to 50 km | solid rock |
| Mantle | 2,900 km | hot, slowly flowing rock |
| Outer core | 2,200 km | liquid metal |
| Inner core | 1,220 km (radius) | solid metal |
Common mistakes
- "The middle of Earth is a pool of lava." Lava is melted rock on the surface. Most of the inside is solid except the outer core.
- "The crust is very thick." In proportion, it is about as thin as the skin of an apple.
- Mixing up magma and lava. Magma is underground; lava is on the surface.
Quick quiz
Layers of the Earth
Check what you know with 4 quick questions.
Question 1 of 4
Which layer do we live on?
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Related topics
Volcanoes
A volcano is an opening in Earth's crust where hot melted rock, gases and ash escape. Over time the cooled lava and ash can build a mountain.
Plate tectonics
Plate tectonics is the idea that Earth's outer shell is broken into huge slabs called plates that slowly move. Where they meet, mountains rise and earthquakes and volcanoes happen.
Earthquakes
An earthquake is a sudden shaking of the ground. It happens when rocks along a crack in Earth's crust, called a fault, suddenly slip past each other.
Adaptation
An adaptation is a feature or behaviour that helps a living thing survive where it lives. A polar bear's thick fur and a cactus's spines are adaptations.
Amphibians
Amphibians are cold-blooded animals with thin, moist skin that live part of their lives in water and part on land. Frogs, toads, newts and salamanders are amphibians.
Birds
Birds are warm-blooded animals with feathers, wings and a beak. They lay hard-shelled eggs, and most can fly. Penguins, ostriches and parrots are all birds.