Observed Distribution Of South American Relief Features

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most solids, it will deform if long-term stress is applied. Presently, there are more than fourteen plates in the Earth�s crust. Upwelling hot magma flows out from mid-ocean ridges and then cools down when exposed to the cooled environment outside; the layer of cooled magma forms the lithosphere. When magma flows out from the ridges, the crust is fractured and a new ocean floor is built spreading perpendicularly away from the ridge. Because of this constant upwelling, the ocean is relatively shallow in these areas. Sea floor spreading and continental drift are the products of this continual upwelling as you can see in the relief maps of South America.
The cooled magma will, in time, sink back down into the Earth in the deep ocean trenches. The mantle sinking down produces subduction zones or Benioff zones. The deepest part of the ocean resides in these areas. There are three types of boundaries where plates meet. They are Divergent boundaries�the upwelling of magma; convergent ...

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