| Forces acting on plates |
There are many forces acting on the plates.
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| Above: Forces acting on the plates (Cox and Hart, 1986) | |
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| This force is a sort of traction
that comes from the contact between the asthenosphere and the
lithosphere. It acts on the bottom of the plate and is proportional
to the plate area and velocity.
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| Mid-ocean ridges rise above the
ocean floor creating a gravitational potential energy, which is
responsible for this force. The resulting effect is that the
lithosphere slides down and away from the ridge along the
lithosphere-asthenosphere boundary.
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| Slab pull is caused by
subduction. A subducting part of the lithosphere is more dense than
the underlying asthenosphere, so it will sink down. Slab drag comes
from the "viscous drag" as the slab sinks.
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| These two forces are frictional
forces. They are generated along plate boundaries as plates try to
move past each other or bump into one another.
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| It is possible that suction is
responsible for a continental plate moving toward a trench. A
likely cause of this suction is eddies produced by the plate
subduncting down the trench causing the asthenosphere to swirl up under
the continental plate. Another cause could be that the trenches are
moving toward the basin center. As the trench is migrating the
subducting slab is plowing through the asthenosphere. This causes a
displacement of asthenosphere on the continent side of the trench.
The continent is therefore sucked toward the trench.
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