Structure of the Earth

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Structure of the Earth

• Earths Interior is divided into 3 layers that
  have very different properties

• Crust
• Mantle
• Core

• Our knowledge of these layers has come mainly
  from the study of earthquake waves.

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The Crust

• The crust is the outer-most layer of the Earth.

• It is between 5 and 100 kilometers thick.

• It is the thinnest of the Earths layers.

• It is where we live.

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The Crust

• The crust is made up mostly of oxygen, silicon
  aluminum.

• There are two types of crust
• Oceanic crust
• Continental crust

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Types of Crust

• Oceanic crust is the crust that lies below the
  Earths oceans.
• It consists mostly of basalt a dark, dense
  igneous rock with a fine-grained texture.

• Continental crust forms the continents and
  consists mostly of granite - a less dense
  igneous rock with larger crystals that is usually
  light in color.

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The Mantle

• The next layer after the crust is the mantle.

• It lies from about 40 to 2,900 kilometers below
  the surface.

• It is much thicker than the crust.

• It contains about 67 of the Earths mass.

• It is a layer of hot rock.

• The mantle is denser than the crust.

• It consists of a number of zones.

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L I T H O S P H E R E
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• The crust and the uppermost part of the mantle
  are very similar. They are both rigid.

• Together they are called the lithosphere.

• Litho means stone.

• The lithosphere is about 100 kilometers thick.

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The Mantle

• As you go deeper into the mantle, heat and
  pressure increase.

• This makes the rock less rigid.

• It has the consistency
• of tar and can bend much like plastic (semi
  molten).

• This plastic-like layer of the mantle is called
  the asthenosphere.

• The lithosphere floats on top of the
  asthenosphere.

• Beneath the asthenosphere solid mantle material
  extends all the way to Earths core.

• This lower solid part of the mantle is called the
  mesosphere.

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The Core

• The layer of the Earth that extends below the
  mantle to the center of the Earth is the core.

• The core makes up about 1/3 of the Earths mass.

• It has two layers
• A liquid outer core
• A solid inner core

• Both are made of iron and nickel.

• Despite enormous pressure, the molten metal of
  the outer core behaves like a thick liquid.

• The inner core is a dense ball of solid metal.

• The pressure is so great that the iron atoms
  cannot spread out and become a liquid.

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Earths Magnetic Field

• Currents in the liquid outer core cause the solid
  inner core to spin.

• The inner core spins at a slightly faster rate
  than the rest of the planet.

• This movement creates the Earths magnetic field,
  which causes the entire Earth to act like a giant
  bar magnet.

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Review

• The Earth is made of three basic layers.

• The crust and the top, rigid part of the mantle
  make up the lithosphere.

• The plastic-like layer of the mantle is called
  the asthenosphere.

• The innermost rigid part of the mantle is called
  the mesosphere.

• The core has two parts.

• The outer core is liquid.

• The inner core is solid.