# Core of the Earth: Facts, Composition, Layers & Temperature

Coming up next: Earth's Mantle: Definition & Facts

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• 0:05 Chemical Layers
• 1:15 The Core of the Earth
• 2:21 Magnetic Field
• 3:14 Other Kinds of Layering
• 3:32 Lesson Summary
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Lesson Transcript
Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

This lesson will discuss the layers of the Earth, focusing particularly on the Earth's core, including its chemical composition, temperature, and how the core creates the Earth's magnetic field. A short quiz will follow.

## Chemical Layers

You might say the Earth is like a gigantic layer cake, with colorful angel cake layers, cream fillings, and a spread of icing on the top. Now that I've made you desperately hungry, let's take a closer look at two of those layers: the inner and outer core.

After Isaac Newton released his laws of motion, Edmund Halley was the first person to use those laws to try to figure out the structure of the Earth. He proposed a hollow model for the Earth -- it seemed like the Earth couldn't possibly be solid. Based on his calculations, he thought the Earth must be made of a series of hollow shells. Though Newton's laws were actually correct, his calculations about the density of the Earth and Moon relative to each other were quite wrong. Thus, Halley's supposition about the Earth being hollow was wrong as well.

The most common way of layering the Earth is based on chemical composition, based on the elements present in different parts of the Earth. When you do that you end up with four main layers: the crust, the mantle, the outer core and the inner core.

The crust is like the icing on the cake, and the mantle is the layers of angel cake. But let's take a closer look at the core of the Earth.

## The Core of the Earth

Below the mantle of the Earth is the core, which is the very center of the Earth, made mostly of heavy metals, especially iron. The outer core is in the liquid state, and so this is like the Earth-cake's cream filling. The inner core on the other hand is solid and contains at least 90% iron. The inner core can be thought of as a final layer of dense pound cake.

The outer core goes from a depth of 2550 km, down to 4750 km, and the inner core continues to the center of the Earth at a total depth of 6470 km.

The temperature as the outer edge of the core is 4500 degrees Celsius, just under the boiling point of copper. From there the temperature gradually increases to a toasty 5400 degrees Celsius at the very center of the Earth, hotter than the boiling point of iron and gold. The only reason the iron in the core doesn't boil away is due to the incredibly high pressures, holding it together as a solid.

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