Earth's Layers

The Earth's Layers

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The structure of the earth is divided into four major components: the crust, the mantle, the outer core, and the inner core. Each layer has a unique chemical composition, physical state, and can impact life on Earth's surface.

Earth's Layers

Mantle

Inner C

Crust

Outer C

The remainder of the Earth is covered by oceanic crust. This type of crust is young — none older than 170 million years — and is only about 8 kilometers thick.

The Earth's crust is its lightest, most buoyant rock layer. Continental crust covers 41percent of the Earth's surface, though a quarter of that area is under the oceans. The continental crust is 20 to 80 kilometers thick. Its rocks hold four billion years of Earth history.

Crust

The temperature of the mantle varies greatly, from 1000°C (1832°F) near its boundary with the crust, to 3700°C (6692°F) near its boundary with the core.

The rocks that make up Earth’s mantle are mostly silicates—a wide variety of compounds that share a silicon and oxygen structure.

The mantle is the mostly solid bulk of Earth's interior. The mantle lies between Earth's dense, super-heated core and its thin outer layer, the crust. The mantle is about 2,900 kilometers (1,802 miles) thick, and makes up a whopping 84 percent of Earth’s total volume.

Mantle

The hottest part of the core is actually the Bullen discontinuity, where temperatures reach 6,000° Celsius (10,800° Fahrenheit)—as hot as the surface of the sun.

The liquid metal of the outer core has very low viscosity, meaning it is easily deformed and malleable. It is the site of violent convection. The churning metal of the outer core creates and sustains Earth’s magnetic field.

The outer core, about 2,200 kilometers (1,367 miles) thick, is mostly composed of liquid iron and nickel. The NiFe alloy of the outer core is very hot, between 4,500° and 5,500° Celsius (8,132° and 9,932° Fahrenheit).

Outer core

The liquid outer core separates the inner core from the rest of Earth, and as a result, the inner core rotates a little differently than the rest of the planet. It rotates eastward, like the surface, but it’s a little faster, making an extra rotation about every 1,000 years.

The temperature of the inner core is far above the melting point of iron. However, unlike the outer core, the inner core is not liquid or even molten. The inner core’s intense pressure—the entire rest of the planet and its atmosphere—prevents the iron from melting.

The inner core is a hot, dense ball of (mostly) iron. It has a radius of about 1,220 kilometers (758 miles). Temperature in the inner core is about 5,200° Celsius (9,392° Fahrenheit).

Inner Core