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Earthquakes , Volcanoes, and Tsunamis

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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 Earth s surface ... – PowerPoint PPT presentation

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Title: Earthquakes , Volcanoes, and Tsunamis


1
Earthquakes , Volcanoes, and Tsunamis
2
Earthquakes
3
Earthquakes
4
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

5
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

6
Earthquakes
7
Volcanoes
8
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

12
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

13
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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