Earthquakes , Volcanoes, and Tsunamis

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Earthquakes , Volcanoes, and Tsunamis
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Earthquakes
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Earthquakes
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Earthquakes

• Plate movements cause large forces
• The rock breaks, and this break can sometimes be
  tens of kilometers long
• Faults are fractures in the Earths surface
• When the rocks break, the rocks on either side of
  the fracture plane slide past one another, until
  the forces are relieved
• Strong vibrations are produced and these are felt
  as an earthquake

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Earthquakes

• Lots of the biggest earthquakes are along
  subduction zones (where the plate is sliding
  downwards)
• A transform fault is found at a transform
  boundary
• If the fault is locked for a long time, and
  suddenly slips, a major earthquake happens
• If the fault slips all the time, there are lots
  of minor earthquakes
• San Andreas Fault, in California, is a long
  transform fault it is locked around San
  Francisco and around Los Angeles

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Earthquakes
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Volcanoes
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Volcanoes

• a volcano is a place where molten rock, and also
  solid volcanic fragments and volcanic gases are
  erupted as the Earths surface
• Sometimes rock that is deep in the Earth is
  melted, to form magma
• Magma rises upward because it is less dense than
  the surrounding rock
• It does not always reach the surface before it
  turns to rock again
• If it does reach the surface, it forms a volcano

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Volcanoes

• Volcanoes erupt for different reasons
• How much gas is in the magma will effect its
  eruption
• As magma gets close to the surface, the pressure
  decreases, and gas bubbles out of the magma
• Magma with low gas content does not have violent
  explosions, unlike that with high gas content
• Large, explosive volcanoes are the most dangerous

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Volcanoes

• Most big volcanoes occur along subduction zones
• Hot spot volcanoes are caused by a hot spot in
  the mantle that will continue to generate magma
  for a long time
• Hot spots dont move, so a line of volcanoes will
  form as the plate moves. The way the volcanoes
  form shows the direction and speed that the plate
  moved
• Eg. Hawaiian Islands are hot spot volcanoes

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Subduction Zones

• There are plenty of major earthquakes and
  volcanoes
• Most of the Pacific Oceans has subduction zones,
  and so we see the Ring of Fire

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Subduction Zone
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Tsunami

•  tsunami  is a series of water waves caused by
  the displacement of a large volume of a body of
  water
• approximately 195 have been recorded in Japan
• immense volumes of water and energy are involved,
  so tsunamis can devastate coastal regions.
• Casualties can be high because the waves move
  faster than humans can run.
• Earthquakes, volcanic eruptions and other large
  distubances can cause tsunamis

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