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Ch1L2
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What causes subduction?
Cool, dense oceanic crust collides with less dense continental crust. The oceanic crust sinks because it is more dense.
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What is subduction?
The process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle again
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What is sonar?
A device that uses sound waves to measure the distance to an object
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What happens to an ocean surrounded by many trenches?
It shrinks because subduction occurs in more places.
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What forms the longest mountain chains on Earth?
Mid-ocean ridges
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What is a mid-ocean ridge?
Long chains of mountains that rise up from the ocean floor
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What is a deep-ocean trench?
Underwater canyons where subduction occurs
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Where does subduction occur?
Deep-ocean trenches
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How often is the ocean floor renewed?
Every 200 million years
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What is sea-floor spreading?
The process that adds more crust to the ocean floor by continually adding new material
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Where does sea-floor spreading happen?
Mid-ocean trenches
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What happens to older strips of rock as new material is added to the ocean floor?
They move outward from either side of the mid-ocean ridge
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What may happen to an ocean with very few trenches?
It may grow larger because subduction occurs in fewer places.
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What are two processes that can change the shape and size of the oceans?
Sea-floor spreading and subduction
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