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23 Cards in this Set
- Front
- Back
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An example of a Constructive plate boundary? |
The Mid Atlantic Ridge (Mid Oceanic Ridge) |
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Where is the MAR? |
At the boundary between N-America and the Eurasian plate in the N-Atlantic and the S-American and African plate in the S-Atlanitc |
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Why has the MAR formed? |
The rising convection currents cause the ocean floor to uplift creating the MAR |
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What is a rift zone? |
A zone of hundreds of parallel fissures on the seafloor |
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What do rift zones form? |
Seamounts and pillow lavas |
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What is seafloor spreading? |
When the lave cools and solidifies to create new oceanic crust so the ocean basin gets wider |
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What are other features associated with constructive plate boundaries? |
Rift Valley, Shield Volcanoes, Seamounts, Pillow Lavas, Black Smokers, The Great African rift valley and Shallow Focus Earthquakes |
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What is a Rift Valley? |
A cleft in the middle of the ridge that is created by tension as the two plates pull apart |
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Example of a Rift Valley? |
Thingvellir, Iceland |
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What is a Shield Volcano? |
A volcano with gentle sides and frequent, gentle eruptions |
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How are Shield Volcanoes formed? |
As plates diverge, magma rises to fill any possible gaps along the plates, creating new oceanic crust |
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Why does the solid, hot mantle rocks turn to liquid? |
As they move us, the pressure drops meaning they can turn to liquid |
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What are Seamounts? |
Volcanoes that are fully submerged by sea, reaching 1000m |
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How are Seamounts formed? |
Submarine volcanoes that do not reach sea level |
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How are Seamounts formed? |
As the volcanoes drift away from the ridge, they lose their magma source and become extinct, gradually becoming eroded |
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What are Pillow Lavas? |
A lump of lava with a crust |
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How are Pillow Lavas formed? |
When molten lava breaks through on the ocean floor it is quickly cooled by the seawater and a crust forms around the lump. Pressure builds until lava breaks through the new crust and oozed out to form another pillow |
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What are Black Smokers? (Hydrothermal vent) |
Fissures on the floor of the sea out of which flows water that has been heated by underlying magma |
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What is the Great African Rift Valley? |
Where the African plate is splitting in to new plates. |
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What is it like? |
Magma has risen through the surface and created volcanoes such as Kilimanjaro |
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What are Shallow Focus Earthquakes? |
They are earthquakes that occur the length of the MOR |
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How do they occur? |
They are caused by the pulling apart of two plates, and so can occur along normal faults |
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How else can they form? |
Along the Transform faults, which occur at right angles to the ridge |
