Anatomy
The Earth, layer by layer
From the solid iron heart at the centre to the edge of space — every shell of our planet, what it is made of, and what it does.
See the cut on the globeInterior
Inner core
- Where
- 5,150–6,371 km deep
- Made of
- Solid iron and nickel
- Temperature
- about 5,400 °C — as hot as the Sun's surface
- What it does
- Immense pressure keeps it solid despite the heat. As it slowly grows it releases the energy that keeps the liquid core above it churning.
Interior
Outer core
- Where
- 2,890–5,150 km deep
- Made of
- Liquid iron and nickel
- Temperature
- 4,000–5,400 °C
- What it does
- A swirling ocean of molten metal. Its motion works like a dynamo and generates Earth's magnetic field — the invisible shield that deflects the solar wind and lets life persist.
Interior
Mantle
- Where
- 35–2,890 km deep
- Made of
- Solid silicate rock, rich in magnesium and iron
- Temperature
- 500 °C near the top to 4,000 °C at the base
- What it does
- By far the thickest layer — most of Earth's volume. Though solid, it creeps over millions of years, and that slow churning drags the plates that raise mountains, open oceans and shake the ground.
Interior
Crust
- Where
- 0–70 km deep
- Made of
- Basalt under the oceans, lighter granite under the continents
- Temperature
- from the surface up to about 400 °C at its base
- What it does
- The thin, brittle skin we live on — only a few kilometres thick under the sea, up to ~70 km under the highest mountains. Everything we build and grow sits on it.
Atmosphere
Troposphere
- Where
- 0–12 km up
- Made of
- 78% nitrogen, 21% oxygen, plus water vapour
- Temperature
- +15 °C at the ground down to −55 °C at the top
- What it does
- The air we breathe. Almost all of the atmosphere's mass and all of its weather — clouds, rain, storms — live here.
Atmosphere
Stratosphere
- Where
- 12–50 km up
- Made of
- Thin, dry air; the ozone layer sits near its top
- Temperature
- −55 °C at the bottom rising to about 0 °C
- What it does
- Its ozone soaks up the Sun's harmful ultraviolet, warming the layer and shielding life below. Airliners cruise just inside its calm base.
Atmosphere
Mesosphere
- Where
- 50–85 km up
- Made of
- Very thin air, too high to breathe
- Temperature
- 0 °C falling to about −90 °C
- What it does
- The coldest layer of all — and the one where most meteors burn up, leaving the bright streaks we call shooting stars.
Atmosphere
Thermosphere
- Where
- 85–600 km up
- Made of
- Sparse gas, torn into charged ions by the Sun
- Temperature
- up to 2,000 °C
- What it does
- The auroras glow here and the Space Station orbits within it. The gas is so thin that its great heat would not feel hot to the touch.
Atmosphere
Exosphere
- Where
- 600–10,000 km up
- Made of
- Stray atoms of hydrogen and helium
- Temperature
- no meaningful temperature — the air is barely there
- What it does
- The atmosphere's faint outer fringe, thinning until atoms drift off into space. Many distant satellites orbit through it.
Space
Space
- Where
- beyond ~100 km (the Kármán line)
- Made of
- Near-vacuum, dotted with the odd particle
- Temperature
- −270 °C in shadow, searing in direct sunlight
- What it does
- By convention space begins at the Kármán line, 100 km up — the height where the air is too thin to fly through and only orbit will keep you up.
The layersPick a layer to read about it.
Interior
Atmosphere
Space