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6.5: Reading- Characteristics of the Inner and Outer Core

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    Do you want to take a journey to the center of the earth?

    Molten metal being poured from an extremely hot container

    Jules Verne’s imagined core was fiery. But we know that the outer core is molten metal, as seen above. As hot as a journey to Verne’s center of the earth might have been, a visit to the real location would be worse.

    iron meteorite
    Figure 1. An iron meteorite is the closest thing to the Earth’s core that we can hold in our hands.

    At the planet’s center lies a dense metallic core. Scientists know that the core is metal because:

    1. The density of Earth’s surface layers is much less than the overall density of the planet, as calculated from the planet’s rotation. If the surface layers are less dense than average, then the interior must be denser than average. Calculations indicate that the core is about 85% iron metal with nickel metal making up much of the remaining 15%.
    2. Metallic meteorites are thought to be representative of the core. The 85% iron/15% nickel calculation above is also seen in metallic meteorites (Figure 1).

    If Earth’s core were not metal, the planet would not have a magnetic field. Metals such as iron are magnetic, but rock, which makes up the mantle and crust, is not.

    Scientists know that the outer core is liquid and the inner core is solid because:

    1. S-waves do not go through the outer core.
    2. The strong magnetic field is caused by convection in the liquid outer core. Convection currents in the outer core are due to heat from the even hotter inner core.

    The heat that keeps the outer core from solidifying is produced by the breakdown of radioactive elements in the inner core.

    Explore More

    Use this resource to answer the questions that follow.

    A link to an interactive elements can be found at the bottom of this page.
    1. What materials can P-waves travel through?
    2. What materials can S-waves travel through?
    3. How do we know the outer core is liquid?
    4. What happens to P-waves when they go through a liquid?
    5. What do P-waves tell about the inner core?

    Contributors and Attributions

    CC licensed content, Shared previously
    All rights reserved content
    • INGE LEHMANN : How Inge Lehmann used Earthquakes to discover the Earthu2019s inner core. Authored by: Chandresh S. Located at: https://youtu.be/ELZ3B4flqNk. License: All Rights Reserved. License Terms: Standard YouTube License

    This page titled 6.5: Reading- Characteristics of the Inner and Outer Core is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Lumen Learning via source content that was edited to the style and standards of the LibreTexts platform.