Structure of the Earth

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Terrestrial planets are planets that are made up mostly of rock. Like all terrestrial planets, Earth is made up of different layers. Earth has four layers: the inner core, the outer core, the mantle, and the crust.

Each layer is a little different from the other, but they all can affect life on Earth.

Structure of the earth

The Inner Core

The inner core is at the very center of Earth. It is mostly a giant, dense ball of iron. The inner core has a radius of 758 miles.

The temperature of the inner core is 9,392 degrees Fahrenheit. That is about 6,000 times hotter than temperatures we experience on the surface!

The inner core is under an immense amount of pressure. The iron found at the inner core should be liquid because of the incredible temperature, but the pressure is so strong that the iron atoms cannot move from a solid state.

Inner Core

The Outer Core

The outer core separates the inner core from the mantle. It is made of mostly iron and nickel.

The outer core is also a little cooler than the inner core. It has a temperature of between 8,132 to 9,932 degrees Fahrenheit.

Like the Earth as a whole, the outer core rotates. The movement of the outer core creates the Earth’s magnetic field. The magnetism of the outer core is about 50 times stronger than that of the surface.

Without the Earth’s magnetic field, solar wind from the sun would destroy the planet’s ozone layer.

The Mantle

The mantle makes up most of Earth’s volume – a whopping 84%! The mantle is 1,802 miles thick.

The mantle is mostly solid. The rocks found in the mantle are compounds called silicates. An example of a silicate is garnet.

While the mantle is mostly solid, it can still move. Around tectonic plates there is a huge amount of pressure that causes the mantle to move over a very long time.

Mantle Convection

There are four separate areas of the mantle: the upper mantle, the transition zone, the lower mantle, and “D Double Prime.”

The upper mantle is the area closest to the crust. It is the coolest part of the mantle and is mostly solid.

The transition zone is the area found between the upper and lower mantle. It is between 255 and 410 miles beneath the Earth’s surface.

The lower mantle is found between 410 and 1,678 miles beneath the surface. It is hotter and denser than both the upper mantle and the transition zone.

“D Double Prime” is the area that separates the outer core from the lower mantle. In some places it is very thin, and in other areas it is thick with rock and iron.

The Crust

The thinnest layer of Earth is the crust. There are two parts to the crust: continental crust and oceanic crust.

Continental crust is where we live. It is between 5 and 40 miles thick. Most of the continental crust is made up of a rock called granite.

The oceanic crust is thinner than the continental crust. It is about 5 miles thick and made up of a rock called basalt.

Interesting Facts

  • Earth is older than the core
  • Some scientists consider the inner core to be plasma and not solid
  • The hottest part of the core is the Bullen discontinuity where temperatures exceed 10,800 degrees Fahrenheit
  • The geomagnetic poles of Earth flip every 200,000 to 300,000 years

Earth Science

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