SME
Grade 12 Science · Problem type
How plates build mountains
Use this for “Why are there volcanic mountains along a coast where an ocean plate sinks?” and “What happens as a rift valley widens?”
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The dense ocean plate sinks under the continent.
Water squeezed out of it melts the mantle above.
The magma rises to build a volcanic arc and coastal mountains, like the Andes.
Assumptions
•
Mantle convection and the pull of sinking slabs move the plates.
•
Where plates push together the crust thickens into mountains; where they pull apart it thins and sinks.
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