Earth: the home planet

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Earth the home planet
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Earths Interior
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Earths Layered Structure

• Earths interior consists of layers
• Layers are arranged according to density
• Most dense material is at the center core
• Density decreases outward
• Density layering includes the hydrosphere
  (oceans) and atmosphere

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Thickness and Composition of Earths Layers
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Earths Temperature Structure
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How Do We Know?
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Refraction of Seismic Waves
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Seismic Waves

• Refraction change in speed and direction when
  passing through a material of different density.

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Other Evidence

• Refraction of seismic waves
• Density of the entire planet
• Gravity (mass) of entire planet
• Composition of meteorites
• Existence of magnetic field

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Earths Magnetic Dynamo
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Earths Magnetic Field
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Was it always this way?

• Accretion of the protoplanet
• Homogeneous structure
• Density differentiation

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Density Differentiation

• Gravitational effects vary with density of
  material
• Materials must be free to move
• Requires plastic flow or fluid flow
• Requires heat

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Earth The Unfinished Planet

• Earth continues to lose heat
• Volcanism brings material to Earths surface
• Other processes (subduction) return more dense
  material to interior
• Conclusion
  Earth is still under construction!

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Implications of anUnfinished Planet

• Volcanism
• Earthquakes
• Atmospheric and climate change
• Effects on life

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Theory of Plate Tectonics

• Earths lithosphere (crust uppermost mantle) is
  divided into plates
• Plates move as a result of heat inside the Earth
• Plates interact to cause
• Earthquakes
• Volcanos
• Mountain systems

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What makes the plates move?

• Uneven distribution of heat in the upper mantle
  (Asthenosphere) causes heat to rise in some
  places
• Differences in density cause colder, more dense
  Lithosphere to sink back into the asthenosphere
• This Convection drives the motion of the plates

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Interactions between Plates cause

• Earthquakes
• Volcanos
• Formation of mountains
• Formation of ocean basins
• Increase amount of continental lithosphere