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What occurs at plate boundaries that are associated with seafloor spreading?
Question Date: 2008-09-25
Answer 1:

There are three types of boundaries that can occur if you consider the relative movement of two spherical caps on a sphere:

1. Converging where one plate dives beneath the other. An example is what happens off the coast of Japan where the pacific plate dives underneath the Asian plate
2. Diverging boundary: two plates move away from each other. In this case, material from below rushes up to fill the crack. This is how NEW CRUST forms
3. Strike slip boundary. This is where the two plates slide past each other --an example is the san Andras fault. It represents the boundary between the North American and pacific plates. If we hold the pacific plate fixed, the NA plate is moving NNW at about 3 inches per year. In about 40 million years LA will be in the Aleutian Islands and will dive underneath back into the earth interior.

Answer 2:

Oceanic crust is very dense compared with continental crust, so it sinks beneath continental crust. Ocean crust can be pulled in two opposite directions because this sinking of oceanic crust beneath continental crust. When this happens, the two plates of oceanic crust being pulled in opposite directions move apart, leaving a void at the plate boundary. Magma fills the void where it cools to create new oceanic crust. It is a continual process. The new oceanic crust continues to be pulled away from the plate boundary because of the sinking of oceanic crust beneath continental crust, and new magma continues to fill the void created by spreading of the sea floor.

Answer 3:

As ocean plates are pulled apart from each-other, faulting occurs resulting in extremely thin ocean crust. The extremely thin crust allows the Earth's mantle to ooze in underneath. Partial melting of the upper mantle occurs underneath the divide due to the reduction in pressure by the thinned crust. The magma that results from this comes up through swarms of dikes that sometimes but not always breaks the surface, filling in the cracks created by the stressed crust, and forming new crust at the boundary.

Answer 4:

At plate boundaries associated with seafloor spreading (divergent plant boundaries) the Earth's crust is very thin and is pulled apart at a slow rate. As the plates separate, magma that is buoyant and just below the crust 'bubbles' up and is instantly cooled by the ocean. This now cooled crust is attached to the plate and as the plate moves apart this happens over and over again.

Here is a link to a great website that shows this in action:


Answer 5:

Seafloor spreading accounts for roughly 80% of the world's volcanism.At spreading centers, new plates (continental crust) are created. Where plates spread apart from each other, earth material (called basalt) rises up to fill the void. The basalt wells up as molten magma extruding through effusive (non-explosive) volcanic vents submersed on the sea floor. Underwater, this molten materiel moves out, and then cools to create the most common rock on the earth, basalt. Basalt is a heavy (dense), black rock formed of the minerals plagioclase-feldspar and olivine, and it is derived directly from the earth's mantle. Two-thirds of the earth is covered by ocean, and oceanic plates are made up of basaltic oceanic crust.

When spreading centers initiate on continental crust (above land), these regions can be called continental rift zones. Eventually the two continental plates will move far apart and the ocean will flood the basaltic crusts low-lying land.

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