What Causes Earthquakes and Volcanoes

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Unit D Chapter 1 Lesson 3

• What Causes Earthquakes and Volcanoes?

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Plate Movements Cause Earthquakes

• Earthquake
• Release of energy as vibrations that results from
  a move in the tectonic plates or volcanic
  activity.
• Focus
• The point in Earths crust where the first major
  movement along the fault occurs.
• Epicenter
• The point on the Earths surface directly above
  the focus of an earthquake.

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Earthquake waves

• Seismic waves
• The waves of energy caused by the sudden breaking
  of rock within the earth or an explosion. They
  are the energy that travels through the earth and
  is recorded on seismographs.
• P wave
• Primary Waves or Push-pull waves that cause
  back-and forth vibrations in the same direction
  as the waves move.

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Earthquake waves continued

• S wave
• Secondary Wave is the second wave you feel in
  an earthquake. An S wave is slower than a P wave
  and can only move through solid rock. This wave
  moves rock up and down, or side-to-side.

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Earthquake waves continued

• Surface Waves
• Waves that travel only at eh surface and move
  less quickly than P and S waves.
• Love Waves
• The first kind of surface wave is called a Love
  wave, named after A.E.H. Love, a British
  mathematician who worked out the mathematical
  model for this kind of wave in 1911. It's the
  fastest surface wave and moves the ground from
  side-to-side.

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Earthquake waves continued

• Rayleigh Waves
• The other kind of surface wave is the Rayleigh
  wave, named for John William Strutt, Lord
  Rayleigh, who mathematically predicted the
  existence of this kind of wave in 1885. A
  Rayleigh wave rolls along the ground just like a
  wave rolls across a lake or an ocean. Because it
  rolls, it moves the ground up and down, and
  side-to-side in the same direction that the wave
  is moving. Most of the shaking felt from an
  earthquake is due to the Rayleigh wave, which can
  be much larger than the other waves.

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Earthquake waves continued

• Seismograph
• An instrument that detects earthquake waves.
• Seismogram
• The paper that has the recorded waves from an
  earthquake on it.

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Earthquake Safety

• Richter scale
• This is a scale that measures the amount of
  energy released during and earthquake.
• Mercalli scale
• Measures the amount of damage that an earthquake
  causes.

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