Inside the Earth

Artwork showing Earth's internal layers

Geologists study how earthquake waves travel through the planet to understand its inner structure. They are still refining their interpretations, but the evidence suggests the following:

Earth has a solid, dense, iron-rich inner core surrounded by a fluid outer core, also mainly iron.

The next layer out, the mantle, is split into the lower and upper mantle. Though it is solid rock, parts of the mantle slowly deform. Hotter rock rises and cooler rock sinks through convection, driving the movement of the Earth's plates.

Above the mantle lies the crust upon which we live. The lithosphere incorporates the crust and part of the upper mantle.

Image: Artwork showing the Earth's internal layers (credit: Jose Antonio Peñas/SPL)


Artwork showing Earth's internal layers Inside the Earth

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Inside the Earth

The interior structure of the Earth is layered in spherical shells, like an onion. These layers can be defined by their chemical and their rheological properties. Earth has an outer silicate solid crust, a highly viscous mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core. Scientific understanding of the internal structure of the Earth is based on observations of topography and bathymetry, observations of rock in outcrop, samples brought to the surface from greater depths by volcanoes or volcanic activity, analysis of the seismic waves that pass through the Earth, measurements of the gravitational and magnetic fields of the Earth, and experiments with crystalline solids at pressures and temperatures characteristic of the Earth's deep interior.

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