“Volcanic and seismic events are major pieces of evidence towards proving that plate tectonics theory is valid’ Discuss the extent to which you agree with this statement (40 marks)
The plate tectonics theory was made by a German named Alfred Wegener. He stated that a single continent existed about 300 million years ago named Pangaea and that it split into two continents of Laurasia in the north and Gondwanaland in the south. Today’s continents were formed by further splitting of the two masses.
Evidence to support this theory is that there is that there have been fossils found on both sides of the Atlantic Ocean of land animals which gives us the idea that they must have been together originally. There is also climate evidence for this as there is coal deposits and fern fossils in the Antarctica which shows it used to be more equatorial. There are also glacial deposits in India, South America and Australia which are too hot for glaciers today. Another piece of evidence is Structural trends as if the continents are fitted together then all the mountain ranges line up, suggesting that they have been split. Continents also partially fit together but not totally due to erosion. However each continent has a shelf 150ft below the surface which all fit together perfectly as have not been eroded.
This theory was shown to be maybe correct when the mid-Atlantic ridge was discovered and a similar feature was discovered in the Pacific Ocean. After investigating it was suggested that sea floor spreading was occurring. Evidence for this was from alternating polarity of the rocks that form the ocean crust. Sea floor spreading implies that the Earth’s crust must be getting bigger. As we know this isn’t the case then the plates must be being destroyed somewhere to accommodate the increase in their size at mid oceanic ridges. Evidence was found with the discovery of huge oceanic trenches where large areas of ocean floor were being pulled downwards.
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