Volcanic & Seismic events are major factors towards proving that the plate tectonics theory is valid. Discuss

Volcanic events and their distribution also shows tell tale signs of the presence of plates and are often found at destructive plate margins, where in many cases the oceanic crust is forced below the continental crust, as the lithosphere descends slides below, large amounts of friction is created and in turn heat leading to melting of the crust. At these margins deep-sea trenches can be found, further proving the movement of plates, for example the Mariana trench near Indonesia. This melting of the crust leads to rising less dense basaltic magma that attempts to rise through the harder rock above it through fissures until reaching the surface, resulting in an eruption. It is the location of these eruptions often nearby to many others, linked with the nearby deep sea trench as well as the basaltic lava erupted once from the ocean floor that prove the plate tectonics theory further. Volcanic events can also occur at constructive margins, and rather than crust being destroyed, the spreading ridge forms a crack in the crust where two plates are moving apart creates new crust. These are known as fissure eruptions, where basaltic lava flows take place, an example of this taking place today is the Mid-Atlantic ridge, where brand new crust continues to be made, as the plates diverge the heat created in the upper mantle escapes through the broken crust forming new land through a fissure eruption. These eruptions thus prove the validity of the plate tectonics theory, the constructive margins especially, not only showing that land is being destroyed, but also created while these plates diverge.

As a geographer, this range of volcanic and seismic events help to prove the movement of plates on the earths surface, however the real task was to prove it was on going and at one point there had been a super-continent as explained Wegener. Also as a geographer, further evidence was required in order to help explain the movement of plates, meaning the volcanic and seismic events could not be the only factors towards proving Wegener's theory.

Some of the first evidence towards proving the theory valid was the spreading of the Mid-Atlantic ridge, helping Wegener to explain the process of continental drift. The discovery of Palaeomagnetism showed that the Mid Atlantic ridge (a submerged mountain range) was spreading, giving an explanation to how continents could move over the earth's surface. Surveys of the ocean floor surrounding the mid Atlantic ridge showed that as you moved away from ridge the polarity of the rock changed in regular strips that fitted with records of the geomagnetic reversal, meaning the metal content within the cooled lava followed the magnetic field of the earth at the time it was created. This mean that the rock further away from the ridge was much older, and had been created through a fissure eruption millions of years ago, proving that the spreading ridge was continuous and continues to move today. Thus, giving a much clearer explanation of how the plates could move, rather than just stating they did.

Chain islands such as the volcanic Hawaiian Islands are also living proof that continental drift is taking place. This string of islands, all very similar in composition are neither near a destructive or constructive plate margin and are instead produced through a single hot spot. It is believed that the abnormally hot area of the mantle (the hot spot), produces rising plutons of magma that eventually breaks through the crust forming basaltic shield volcanoes that eventually forms an island, as seen in Hawaii. As the island becomes part of the plate, the on-going continental drift moves the newly formed island away from the hotspot, in turn deeming the volcano dead and the next volcano is formed as the plate moves. The high mineral composition of the cooled lava on Hawaii and other similar islands make it extremely inhabitable, and as a result have been inhabited. It is this movement that not only proves the theory of continental drift, but also helping to explain the make up of the earth below the crust that can explain the movement, such as the semi-molten mantle allowing convection currents to take place.

Further patterns across the earth provide evidence towards proving Wegener's super-continent theory true. The first being continental fit, that when seen on a map would show some continents such as Africa and South America appearing to fit together, it is this particular evidence that links with other biological and geological evidence. Similar fossil formations for example are found in both South America and Africa from the same reptile. As well as fossilised plants are found in both India and Antarctica. Evidence of similar climates can also be seen across a whole host of continents such as North America, Antarctica and the UK, as deposits of coal have been found that can only be produced in tropical conditions, suggesting they over time they have drifted apart.

To conclude, although I believe volcanic and seismic events provide a major factor in helping to prove the plate tectonics theory correct, they do not provide as much of a role as some other unquestionable evidence towards explaining how the movement of plates take place. The seismic waves for example from earthquakes show proof of the earth's inner structure, as only certain waves can travel through solids and liquids, with the liquid structure facilitating convection currents. The volcanic and seismic events are therefore simply effects of the movement of plates, whereas other evidence can prove Wegener's supercontinent theory. So although major factors, there are others that must be included when validating the theory.