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Discuss the Range of Available Evidence Which Supports the Theory of Plate Tectonics. (40 Marks)

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Wegener's theory Continental drift-In 1915, the German geologist and meteorologist Alfred Wegener first proposed the theory of continental drift, which states that parts of the Earth's crust slowly drift atop a liquid core. The fossil record supports and gives credence to the theories of continental drift and plate tectonics.

Pangea was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It formed approximately 300 million years ago and then began to break apart after about 100 million years. Unlike the present Earth, much of the land mass was in the Southern Hemisphere. Pangea was fully assembled by the Early Permian Period, some 270 million years ago. It began to break apart about 200 million years ago, during the Early Jurassic Period, eventually forming the modern continents and the Atlantic and Indian Oceans.The giant ocean that surrounded the continent is known as Panthalassa. The movement of Earth's tectonic plates formed Pangaea and ultimately broke it apart. Pangaea existed during the Permian and Triassic geological time periods, which were times of great change. This therefore shows that a certain extent of tectonic activity took place 200 million years ago to form our world that we know today. The idea of Pangea fitting together in a jigsaw fashion compared to how convection currents dictate the movement of the plate boundaries it can be seen as tangible that these pieces were to fit together very easily, however certain processes of biological and possibly chemical weathering as well as erosion has caused these ‘’pieces’’ to have perhaps lost their shape, meaning they will not fit together as well in this present day.

Also, another piece of evidence that would help to support Wegeners theory would be the fact that Earthworms were found in all Gondwanaland continents, meaning that they must have been transported to these places somehow. What supports this evidence is the fact that earthworms were not known for their swimming ability, meaning that they may have been transported to the Gondwanaland continents. These places consist of all of the countries in the Southern hemisphere eg. Antarctica, South America and also Australasia. Earthworms originally came from North America, therefore meaning that due to the North American plate and the African plate pulling away from each other, certain species of earthworms were therefore taken across the oceano on this plate, after that they died and their fossils have now been discovered, therefore helping to develop the theory of continental drift and plate boundaries. Also, another piece of evidence that could perhaps be used to back up Wegener's theory is the fact that the Appalachians and Caledonian mountain ranges located in North America and Scotland are thousands of miles away from each other yet match up almost perfectly. This could therefore suggest that North America and Scotland were once joined as one piece of land and therefore shared the same mountain range. This helps to back up the theory because had the African plate not been pulling away from the North American plate, it would have perhaps mean that Scotland and North America were perhaps still the same piece of land or country, meaning that these two mountain ranges were part of the same one large mountain range.

However, certain modern day examples would consist of the Mid Atlantic ridge shows that the North American, African and Eurasian plate are pulling away from each other causing a large U shape in the sea bed around Iceland. Due to it being located on a divergent plate boundary, it means that new land is always being formed during this process. This would therefore suggest that these plates are pulling away from each other at a very slow pace. This therefore means that magma is coming up through the gap and forming new land with rock called basalt. However, due to the plates pulling away from each other at such a slow rate, this means that a large U shaped valley is formed underwater, resulting in a 3 km deep ridge in the sea bed. The ridge has an average spreading rate of about 2.5 cm per year, meaning that it will constantly be widening, potentially moving other countries and displacing places like Iceland. However, also due to the vast amount of volcanic activity underneath Iceland, this has caused Iceland to grow in a rather fast pace. It has also lead to the creation of certain island around Iceland, an example of this would be Surtsey island located just off the south of Iceland. It is known as a volcanic island, meaning that it is again located on a divergent plate boundary. With the growth of this island being so quick in the last few years, it goes to show that certain island could have perhaps been formed elsewhere due to continental drift, resulting in new landforms but also a movement in nowadays continents.

Plagio Magnetism is a term used by scientists to determine the pattern of iron on the seabed due to the movement of tectonic plates. However, recent studies have shown that tectonic activity has caused these patterns of iron to have changed in recent times. This therefore means that due to the possible twisting of tectonic plates, it has caused these patterns to be slightly distorted or changed over the years. Again, this can help to back up Wegener's theory and suggest that tectonic activity has caused this to happen by the twisting and movement of tectonic plates. These iron marks are connected to tectonic activity because it shows which way the plates are moving with regards to each other, therefore meaning that because of the shape in which they have changed, it could suggest that the twisting and movement of plates due to convection currents has helped to cause this, therefore helping to support Wegener's theory of continental drift.

There is a large amount of seismic, volcanic, and geothermal activity along the conjectured plate boundaries. Therefore meaning that a large amount of tectonic activity is present along plate boundaries, resulting in the creation of new land or the destruction of land, however regardless of which it is, there is a large amount of available evidence to suggest that Wegener’s theory of plate tectonics and continental drift is correct or perhaps close to what could maybe be the truth.…...

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