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​​​​​​​ Plate tectonics and continental drifts the theory of plate tectonics had enabled us to explain how the contents drift and why there are mountains, earthquakes, volcanoes and so much more.

From our video: The Structure of the Earth, you would have learned that the Earth's thin solid crust lies over the mantle of hot rocks which those solid are able to flow like ice of the place. This movement is caused by convection currents- the currents in the cooler mantle near the surface is more dense so sinks towards the iron core driving hotter, less dense mantle towards the surface. The Earth's crust rides on these slow-moving convection currents.

Over the whole Earth, there are several convection currents which divide the Earth into a number of plates. It's at the boundaries of these plates that interesting things has happened. Notice that the shape of the plates is not the same as the shape of the continents. They are simply carried about floating at the top of the plates because they are made of lighter rocks than the ocean crust. At the boundary of two plates and where the convection current is moving upwards like this. The plates move apart and the new magma, which is molten rock erupts to fill the gap forming new oceanic crust made of basalt, an igneous rock and this is called: the divergent boundary.

A hundren million years ago when dinosaurs roamed the Earth, Europe and America were joined and there was no Atlantic Ocean. These convection currents pulled the two continents apart. First, a Rift Valley formed got flooded with seawater and the new Atlantic Ocean was born. Even today the Atlantic Ocean is spreading about as fastest as your fingernails grow and down the middle, our underwater volcanoes, were strange life forms grow among the so called: black smokers.

If the ocean is spreading in some places it must being consumed in others and this is where two plates are moving towards each other, the so called: convergent boundaries.

Continental rocks get eroded and form a sediment on the ocean floor. As the ocean is carrying down called :subduction, the sediments get carried down or subjected and melt but being less dense that the basalt rock of the ocean crust, get pushed up forming volcanoes along the mountain chain.

Sometimes, the plate simply slide alongside each other as they do in the famous San Andreas Fault in California. The relative movements, in the so called: transform boundary, cased major earthquakes. This would also mean the Los Angeles will come alongside San Francisco in about 20 million years time. Sometimes a convection current in the mantle is upwelling, causing what is so called: a hot spot.

As the plate moves over the hot spot, a series of islands form as we see in Hawaii. Gradually, the older islands get eroded and disappear beneath the ocean.

Oceanic crust is never more than a few million years old because it is constantly being created at mid-oceaning ridges and consumed of sub-ducted at convergent boundaries. However, continental crust has simply been carried around, broken apart and brought together ever since the formation of the earth 450.000 million years go.

So, to the big picture, watch now as we look back in Earth history 250 million years when all the continents were bundle together in what is called: Pangaea. Plate movements broke this up. Here we are, 65 million years ago when the dinosaurs vanished, watch now as the Atlantic Ocean opens up and India crushes into Asia- the world we see today.


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