Earth

1
Earths Structure
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The layers of Earth

• Earth is divided into 3 layers based on chemical
  composition.
• Core Dense metallic center, made up of mainly
  metal iron.
• Mantle Liquid middle layer made up of silicon,
  oxygen and magnesium.
• Crust The solid outer layer made up of silicon,
  oxygen and aluminum.

3
Continental and Oceanic Crust

• There are two types of crust
• Continental Is thicker
• Oceanic is thinner and heavier.
• Compared to the other layers, both types of crust
  are rocky, thin and fractured.

4
The Physical Structure of Earth

• Earth is divided into five layers based on
  physical properties.
• Lithosphere
• Asthenosphere
• Mesosphere
• Outer core
• Inner core

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Lithosphere

• Lithosphere
• cool rigid layer, made up of the crust and upper
  layer of the mantle.
• Lithosphere is divided into pieces called
  tectonic plates.

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Asthenosphere

• 2. Asthenosphere
• Below the lithosphere.
• Made up of slow flowing solid rock.
• The moving rock allow for tectonic plates to move.

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Physical Structure continued

• 3. Mesosphere Slow flowing layer beneath the
  Asthenosphere
• 4. Outer core Layer of liquid Iron and Nickel.
• 5. Inner core Solid iron and nickel, temperature
  is estimated to be between 4000ºC to 5000ºC

8
Mapping Earths Interior

• How can we know so much about Earths interior if
  no one has ever drilled through the crust?
• Earthquakes produce seismic waves, and travel
  thru materials at different speeds.
• Science uses these waves to determine the density
  of each of Earth's layers

9
Continental Drift

• In the 1900s,Scientist Alfred Wagner, viewed the
  continents as puzzle pieces.
• Had a hypothesis that our continents used to be
  one large continent.
• He named his hypothesis the Continental drift
  theory.

10
Evidence for Continental Drift

• Fossils of same plant can be found on continents
  that are from each other.
• Location of mountain ranges with similar rock
  show a pattern.

11
The Breakup of Pangaea

• A single continent Pangaea (250 million years
  ago).
• Split into two continents Laurasia and Gondwana
  (135 ,million years ago).
• Split into today's continents.
• Continents sometimes collided, forming mountain
  ranges and volcanoes.

12
Sea-Floor spreading.

• When Wagner introduced his hypothesis, many
  scientists did not accept it because the strength
  needed to move Earths crust seemed impossible.
• In the 1960s Scientist studying the ocean floor
  discovered identical patterns of magnetism on
  both sides of the mid ocean ridge.
• This was proof that continental drift was
  possible.

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Sea-Floor spreading Continued.

• At a mid-ocean ridge, magma rises through
  fractures in the sea floor.
• As the magma cools it forms new sea floor.
• As this continues to happen, new floor is made
  and older floor is pushed away from the fracture.
• Sea-floor spreading was proven to cause
  continents to move.

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