Layers of the Earth Diagram

If you could dig straight down, you would pass through the thin rocky crust, thousands of kilometres of hot, slowly flowing mantle, a liquid iron outer core and finally a solid iron inner core hotter than the surface of the Sun. This interactive diagram shows each layer; click one to learn about it, drag the depth probe to any depth, or switch to true scale to see how thin the crust really is.

The layers at a glance

The deep values come from seismology — the study of how earthquake waves travel through the planet — and from laboratory experiments on rocks and metals at high pressure. Published estimates vary, especially for temperatures in the core.

How scientists know what’s inside

The deepest hole ever drilled, the Kola Superdeep Borehole in Russia, reached about 12 km — less than 0.2% of the way to the centre. Everything deeper is known indirectly. Earthquake waves speed up, slow down and bend as they pass through materials of different density and stiffness. Shear waves (S-waves) cannot travel through liquid, and they disappear on the far side of the Earth from large earthquakes — the shadow zone that revealed the liquid outer core. Meteorites, which formed from the same material as the early Earth, give clues to the core’s iron–nickel composition.

Crust and lithosphere

The crust is the thin outer skin: about 7 km thick under the oceans and 30–50 km under the continents, reaching 70 km beneath high mountain ranges. The crust and the rigid top part of the mantle together form the lithosphere, which is broken into tectonic plates. These plates move a few centimetres a year over the hotter, softer asthenosphere, causing earthquakes, volcanoes and mountain building at their edges.

The mantle

The mantle makes up about 84% of Earth’s volume. It is solid rock, but over millions of years it flows like extremely thick toffee. Heat from the core and from radioactive decay drives slow convection currents in the mantle, which help move the plates above. A transition zone between about 410 and 660 km marks changes in the mineral structure as pressure increases.

The core

The core begins about 2,900 km down. The outer core is liquid iron and nickel, and its churning motion generates Earth’s magnetic field, which protects the atmosphere from the solar wind and makes compasses work. The inner core, starting about 5,150 km down, is solid despite temperatures around 5,000–6,000 °C, because the enormous pressure — over three million times atmospheric pressure — keeps the metal from melting.

How to use the interactive diagram

1. Click any layer to see its depth, state, temperature and density.
2. Drag the depth probe to see which layer lies at that depth, with approximate temperature and pressure.
3. Switch to true scale to see how thin the crust really is compared with the rest of the planet.
4. Use Numbered mode or the quiz to test yourself, and print a labeled or blank diagram.

Worked example: a journey to the centre

Set the probe to 30 km: you are still in continental crust at around 450 °C. At 100 km you reach the bottom of the lithosphere, near 1,300 °C and over 3 GPa of pressure. At 2,891 km the probe crosses into the liquid outer core, where the temperature jumps to roughly 3,700–4,000 °C and the pressure is about 136 GPa — some 1.3 million times the pressure of the air at sea level. At 6,371 km, the centre, estimates put the temperature around 5,500 °C and the pressure above 360 GPa.

Memory aid

From the outside in: Crust, Mantle, Outer core, Inner core — “Can Mice Organise Ice?” The core is about the size of Mars, the inner core about 70% of the Moon’s diameter, and the crust is thinner, relative to the Earth, than the skin of an apple.