"Plate Tectonics Give and Take" Discuss Essay

1551 Words Nov 6th, 2012 7 Pages
Plate tectonics give and take – Discuss
Plate movement is caused by convection currents in the asthenosphere which is the lower part of the mantle. Heat form radioactive hotspots decays near the core and this residual heat, heats up the surrounding magma causing it to rise. This forms the rising limb of the convection current. When the current reaches the lithosphere, made up of the crust and the upper part of the mantle, the convection currents diverge. As it diverges, it drags the lithosphere with it. The convection current cools and descends forming the descending limb of the convection current. This pulls with it the lithosphere in a process known as dragging. This is proved by the moving of continents as seen in Wegener’s theory. He
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This gives evidence for plate tectonics both giving and taking land away so the earth constantly stay the same size.
There are three different types of plate boundaries that give or take in movement, give new land and take old land and can give or pull away features of the moving plates. The first is a constructive or divergent boundary. This is a boundary between two plates that are moving apart or rifting. The rifting causes sea floor spreading that can be seen by the production of mid –oceanic ridges, rift valleys and fissure volcanoes. As the two plates pull away from each other they give room for basaltic magma to well up from the magma below. This rock solidifies to form the youngest part of the earth’s crust which is continually being created. At these boundaries we find mid oceanic ridges the most famous being the mid Atlantic ridge which extends the whole length of the Atlantic Ocean. The mid Atlantic ridge also provides evidence of plates moving apart from each other as the continents of north and South America and Africa are equidistant from either side of the ridge showing the sea floor is giving way to new crust which is moving the continents further away from each other. Volcanic activity also occurs along these ridges forming submarine volcanoes which sometimes raise above sea level to form islands for example Iceland. This

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