where the plates are pulled apart because of magma which rises through the asthenopsphere creating a gap in the crust where magma rises through.
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mid-ocean ridges
divergent boundaries are mostly found at mid ocean ridges. this is where magma rises through the asthenosphere and to the earths surface. PILLOW LAVES are formed when magma solidifies and forms domes of basaltic rock.
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rift valleys
rift valleys are formed when pillow laves of basaltic rock build up... magma continues to rise cause stresses in the litheoshpere (formng a dome)... eventually the stresses build up causing parallel faults in the dome... this forms RIFT VALLEYS.
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black smokers
these happen at mid ocean ridges where water seeps into a rift valley... the water is then SUPER-HEATED which changes the chemical composition of the basaltic rock... jets of water are created which contain mental sulphides... found on the sea bed.
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rift zones
rift zones are breaks in the crust... these can also happen on LAND (not just underwater) this can cause the continents to break up. (eg rift stretching from Red Sea towards Turkey)
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graben
grabens are sunken rift valley under the water... they are formed because of rift zones where the crust is stretched and faulting happens, then the crust sinks forming this sunken valley. magma continuing to rise causes new boundaries.
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Other cards in this set
Card 2
Front
divergent boundaries are mostly found at mid ocean ridges. this is where magma rises through the asthenosphere and to the earths surface. PILLOW LAVES are formed when magma solidifies and forms domes of basaltic rock.
Back
mid-ocean ridges
Card 3
Front
rift valleys are formed when pillow laves of basaltic rock build up... magma continues to rise cause stresses in the litheoshpere (formng a dome)... eventually the stresses build up causing parallel faults in the dome... this forms RIFT VALLEYS.
Back
Card 4
Front
these happen at mid ocean ridges where water seeps into a rift valley... the water is then SUPER-HEATED which changes the chemical composition of the basaltic rock... jets of water are created which contain mental sulphides... found on the sea bed.
Back
Card 5
Front
rift zones are breaks in the crust... these can also happen on LAND (not just underwater) this can cause the continents to break up. (eg rift stretching from Red Sea towards Turkey)
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