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2.15: Earth's Mantle

Difficulty Level: Basic Created by: CK-12
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What does mantle rock look like?

You can't go to the mantle but small pieces of the mantle can come to you. Kimberlite forms deep in the mantle and is erupted violently into the crust. Kimberlite can contain diamonds. Most kimberlites reached the surface much earlier in Earth history.

Mantle

Beneath the crust is the mantle. The mantle is made of hot, solid rock. They know this because of seismic waves, meteorites and the heat that comes from inside the planet. Mantle rock is mostly peridotite, which is rich in iron and magnesium (See Figure below). Peridotite is rare at Earth's surface.

The rock of the mantle is mostly peridotite. Peridotite is formed of crystals of olivine (green) and pyroxene (black).

Heat Flow

Through the process of conduction, heat flows from warmer objects to cooler objects (Figure below). The lower mantle is heated directly by conduction from the core. In conduction, heat is transferred as atoms collide.

In the process of conduction, heat flows from warmer objects to cooler objects.

Hot lower mantle material rises upwards (Figure below). As it rises, it cools. At the top of the mantle it moves horizontally. Over time it becomes cool and dense enough that it sinks. Back at the bottom of the mantle, it travels horizontally. Eventually the material gets to the location where warm mantle material is rising. The rising and sinking of warm and cooler material is called convection.

The rising and sinking of mantle material of different temperatures and densities creates a convection cell.

Vocabulary

  • conduction: The process in which energy moves from a location of higher temperature to a location of lower temperature as heat. The material does not move, just the heat.
  • convection: The movement of material due to differences in temperature.
  • peridotite: Dense, dark igneous rock that makes up the mantle.

Summary

  • The mantle is composed of solid peridotite.
  • Conduction from the core heats the lower mantle.
  • Mantle convection bring hot material up toward the surface. It brings cooler material down toward the core.

Practice

Use these resources to answer the questions that follow.

http://www.universetoday.com/26717/earths-mantle/

  1. What is the mantle?
  2. How far does the mantle extend?
  3. Where can the mantle be seen?
  4. What is the composition of the mantle?
  5. Why does the mantle flow?

Review

  1. How do scientists know what the mantle is made of?
  2. What is conduction?
  3. How does convection work in the mantle?

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    Vocabulary

    conduction

    Process in which energy moves from a location of higher temperature to a location of lower temperature as heat; only the heat moves, not the material.

    convection

    Movement of material due to differences in temperature.

    peridotite

    Dense, dark igneous rock that makes up the mantle.

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    Difficulty Level:
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    Grades:
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    Date Created:
    Jan 04, 2013
    Last Modified:
    Aug 31, 2016
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