Earth's Layers
From the surface to the core: a cross-section of our planet
Summary
The Earth's interior in cross-section: a hard crust on the outside, a slowly flowing mantle beneath it, then the molten outer core and, at the centre, the solid inner core. Rotate and zoom the model to explore its nested layers.
In depth
We learn about the Earth's interior from seismic waves: earthquake waves travel through different layers at different speeds and bend at the boundaries. The outer crust (30–70 km under continents, 5–10 km under oceans), the mantle beneath it (2,900 km of plastic rock), the outer core (liquid iron-nickel, 2,300 km thick) and the inner core (solid iron-nickel, 1,220 km in radius). Convection currents in the liquid outer core generate the Earth's magnetic field, the invisible shield that protects us from the solar wind. The inner core is at about 5,200°C (about as hot as the surface of the Sun!), yet it stays solid because it is under a pressure of 360 GPa. Mantle convection drives plate tectonics: the continents move 2–7 cm a year, and the Atlantic Ocean is still widening. Digging a tunnel through the centre of the Earth to the other side is physically impossible; but mathematically, a free fall through it would take 42 minutes (assuming gravity weakens as you go and there is no air resistance).
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