Sea Floor Spreading Flashcards
Explain the process of sea floor speeding (4 stages)
- ocean floor is spreading away from the MOR (like a conveyor belt)
- as this happens new crust is made in the central Rift Valley in the MOR
- Solid mantle peridotite creeps to the surface as a part of giant convection currents which force the ocean apart
- Pressure is released in the mantle meaning it partially melts generating magma. Some cools at the base of crust making gabbro, some rides into the crack forming dole rite dykes, some escapes to create basalt pillow lavas
How does the axial Rift Valley show evidence?
We know from observations of rift valley on land they are pulling apart
How does volcanic activity show evidence?
Volcanic activity on East African rift-same occurs on MOR: 2 forms
Hydrothermo vents/black smokers - sea water penetrates through rock towards magma chamber, hot rocks heat water so it rises, as it rises it melts minerals and when it hit the cold sea water minerals precipitate due to temp change so cloud + chimney
Fissure eruptions- along the crack, pillow lavas
How does seismic activity show evidence?
Shallow focus earthquakes occur along the transform faults which cut across the MOR
How does the age of the oceanic crust show evidence?
Age increases as you move away from the MOR (shown by drilling cores)
How does thickness of sediment show evidence?
Older Rock has more time to collect sediment than newer rock so further away the thicker it is
How does palaeomagnetism show evidence?
Earth magnetic field has flipped many times, symmetrical stripes of the way the rocks formed on either side of the MOR show that the floor is spreading
How do hotspots show evidence?
As the sea floor moves over a STATIONARY mantel plume lines of volcanic islands appear
How do satellite observation show evidence?
We can now record the spreading in Iceland which is part of the MOR
What does sea floor spreading explain?
Continental drift
