Evaluate How Plate Tectonics Theory Helps Our Understanding of the Distribution of Seismic and Volcanic Events

The theory of plate tectonics was first developed by Alfred Wegener. He concluded that the continents seem to have a similar shape and could potentially fit together. This suggested that they were at one time joined together as part of 2 super continents called Gondwanaland and Laurasia was in the north. This theory was said to be proven by the discovery of fossilised remains of a mesosaurus that were found on the coasts of Brazil and Gabon. Sea floor spreading is another theory that supports the idea of plate tectonics; this theory discovered that rock is being formed under the ocean as a new sea floor. Sea floor spreading was shown in the Atlantic, where it is believed the Eurasian and North American plates are moving apart on a constructive plate boundary. This occurs via magma rising through a rift and cooling rapidly on the surface creating new sea floor and a ridge of volcanoes called the mid-Atlantic ridge. The eruption of Surtsey in 1963 created a new island which further proved that land and plate were being constructed along this margin. More modern technology has been developed to help prove this theory. One way is carbon dating of the oceanic crust, this has shown that the crust nearer to the UK is far older than crust along the mid-Atlantic ridge. Deep sea exploration has discovered palaeomagnetism. Palaeomagnetism is where metallic elements in the crust are aligned in opposing layers. Every so often the poles flip; This means that each band of the opposing aligned elements in the crust represent several hundred thousand years of crust that was created in that time period.

Many earthquakes and volcanoes are found along the Pacific Ring of Fire. Running close by parallel to these boundaries were very deep ocean trenches eg the Marianas trench, which were the deepest parts of the ocean. Scientists realised that the ocean trenches showed that some plates are sub ducted; This was once again proven by deep sea exploration. Here an oceanic plate which is denser would subduct a continental plate, the plate would melt inside the mantle creating a pool of magma which would rise through the cracks in the rock forming a volcano. It was later discovered that there must be different types of plate boundaries according to the natural hazards that occur. For example earthquakes are distributed along the Eurasian - Australian plate boundary where there are no volcanoes. The theory of plate tectonics explains that oceanic plates, because they are

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