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Earth's Mantle

Earth's mantle is made of dense, dark, hot minerals; heat moves within and from it.

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Earth's Mantle

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 (Figure below). Peridotite is rare at Earth's surface.

Peridotite is formed of crystals of olivine and pyroxene

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

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

Hot lower mantle material rises upward (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.

 

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.

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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