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2.16: Earth's Core

Difficulty Level: Basic Created by: CK-12
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Is this what the core looks like?

Yes! The outer core anyway. The outer core is liquid metal, like in this photo. Of course, the metal is under an incredible amount of pressure.

Core

The dense, iron core forms the center of the Earth. Scientists know that the core is metal. The inner core is solid and the outer core is molten. Here are some of the reasons they know this:

  • Metallic meteorites are thought to be from the same type of material that is found at the core (Figure below).

An iron meteorite is the closest thing to the Earth’s core that we can hold in our hands.

  • Scientists calculate Earth's density from the planet's rotation. To match the total density the inner layers must be denser than the outer layers. They must be as dense as metal.
  • Seismic waves show that the outer core is liquid. The inner core is solid.
  • For there to be a magnetic field, there must be liquid metal. The metal must be convecting. If the core did not have convecting metal, there would be no magnetic field.

Summary

  • Density calculations show that Earth's core is metal.
  • Seismic waves show that the inner core is solid and the outer core is liquid.
  • Metallic meteorites and the magnetic field are also clues about the makeup of the core.

Interactive Practice

Use this resource to answer the questions that follow.

100 Greatest Discoveries: The Core of the Earth at http://science.discovery.com/tv-shows/greatest-discoveries/videos/100-greatest-discoveries-the-core-of-the-earth.htm (2:36)

  1. Who was Richard Oldham?
  2. What did Oldham discover?
  3. Who was Inge Lehman?
  4. What did Lehman discover?
  5. Explain the structure of the core.
  6. How large is the core?
  7. How hot is the core?

Review

  1. What evidence is there that Earth's core is metal?
  2. What evidence is there that the outer core is molten?
  3. Why does Earth have a magnetic field?

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Difficulty Level:
Basic
Grades:
6 , 7
Date Created:
Jan 04, 2013
Last Modified:
Mar 23, 2016
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