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GEOL 101: Intro to Geology > Western Pacific and Indonesia > Flashcards

Flashcards in Western Pacific and Indonesia Deck (5)
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1

How does subduction initiate, evolve and move plates?

  • Initiate: 
    Subduction is the great plate eater. Over time, the crust cools and becomes more dense. At the convergent boundary, this dense plate will sink below the lighter plate.
  • Evolve:
    This sinking begins to pull the plate towards the boundary. This pulling effects all other plates. Sometimes the pull of one plate verses another can push, say, a convergent boundary over the top of a divergent boundary. This would make the divergent boundary extinct because it's existance depends on the less dense, weaker spot in the crust. This hot spot will no longer exist as the dense crust surrounding the convergent boundary moves over the top of it.
  • Move:
    The pulling of a subduction zone will change and effect the directional pull of all other plates. It could be compared to pulling the plug in a bathtub and watching the water and anything floating on the surface move toward the drain.

2

How does subduction cause earthquakes, explosive volcanoes and metamorphismStill need to answer?

  • Earthquakes:
    The pull of the subduction zone is kind of like dragging a book across a table with a rubberband. The friction of the book holds it in place for a time, but once enough pressure builds, then the tension is released and the book 'quakes'
    The subduction zone pulls very slowly over a long period of time, and then once enough pressure mounts, the crust moves. The main point of movement is at the plate boundary where the pulling is occuring. It happens when cool crust radically changes temperature and pressure and goes into the mantle. 
  • Explosive Volcanoes:
    As far as I can tell, subduction zones only happen on oceanic crust because continental crust is not dense enough to be subducted. Therefore, I will only discuss subduction near the ocean. The oceanic crust becomes saturated with water over time. As the crust reaches the subduction zone, cracks form, and more water seeps in. As the crust is pulled deeper into the earth, the water lowers the melting point and causes rock in the lithosphere to become magma. Because of the lowered melting point, this magma is less hot and more felsic. The gas has difficulty escaping and as soon as there is a weak point in the pressure, it will explode. Compare it to popping the quark on a champaign bottle.
  • Metamorphisism:

3

What are the hazards associated with subduction zonescheck?

  • Exploxive Volcanoes
  • Earthquakes
  • Tsunamis

4

Use the concept of stick-slip behavior along plate boundaries to predict where earthquakes are likely to happen within the next 50 years.

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5

  • How earthquakes cause tsunamis?
  • How do we prevent tsunami disasters?finish

  • When the ocean floor ripples, the ocean ripples. Earthquakes make the crust ripple and shake. This causes the water to do the same.
  • You can't prevent a tsunami, however, you can identify subduction zones and use the concept of slip-stick to guess who will be hit next. Then you can spend time preparing or evacuating the people. Japan is a good