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Earth’s Inner Core

The inner core is a layer of the Earth at the very center of our planet. It is a solid ball made out of an iron-nickel alloy and other metals. It is the hottest layer of the Earth and has the highest pressure.

Inside of Earth.

Where is the Earth’s Inner Core?

The inner core is at the center of the Earth, below the outer core. It starts at the bottom of the outer core, which is 5,150 km from the crust. It ends at the very center of the planet, about 6,378 km from the surface of the Earth.

A slice of Earth.

Can you find the inner core? Look below the outer core!

Each year, part of the outer core freezes and becomes part of the solid inner core. So over time, the inner part of the core gets a little bit bigger while the outer core gets smaller.

Characteristics of the Earth’s Inner Core

Temperature – This inner core is the hottest layer of the Earth. The temperature is not the same throughout the entire layer. At the surface, it is about 5,430 degrees Celsius. This is about the same temperature as the surface of the Sun! That’s really hot!

Thickness – The inner core is the second thinnest layer of the Earth. It is a sphere with a radius of about 1,220 km.

A diagram of the inside of the Earth,

Fun Fact: The radius of the Earth’s inner core is about 70% the size of the Moon’s radius.

Composition – This layer is made of metals, like the outer core. It is mostly made up of an iron-nickel alloy. It also contains small amounts of other metals.

State: Unlike the outer core, this layer is in a solid state. This is because there is a lot of pressure so far below the Earth’s surface.

The Discovery

You might be wondering how scientists discovered the Earth’s core. It can be difficult for scientists to know about the inside of the Earth because they can’t actually look at it. Watch this video to learn how scientists discovered the Earth’s core. Hint: It has to do with seismic waves.

Other Great Resources

Brief Overview of the Earth’s Layers: http://gamediv1.weebly.com/inner-core.html

Science Magazine on the Core: http://www.sciencemag.org/news/2010/08/earths-moving-melting-core

The Core and the Structure of the Earth: https://www.dkfindout.com/us/earth/structure-earth/inner-core/

Written By: Leah Tolby.