Theories Of Plate Tectonics

The theory of plate tectonics was formulated in the 1960’s, to provide a realistic and complete idea of the processes that produce the Earth’s surface. These plates make up the Earth’s strong outer layer, the lithosphere. “This layer is about 100km thick, which includes the crust and the uppermost part of the mantle.” (Rafferty, 2010) Before the late 1960’s, geologists held the perspective that all the continents and ocean basins were in fixed positions. However this view was quickly dismissed, as scientists discovered that in fact the Earth’s continents were not static; but instead they glide across the globe. This movement of continents causes land material to collide, distorting the crust and therefore creating some of Earths greatest mountain

Volcanoes are formed when there is an “opening in the earth’s lithosphere that allows lava, volcanic ash, and gases to escape” (Governemnt of Canada, 2016). Thereby, the connection between volcanism and plate tectonics is that “plate motions provide the mechanisms by which mantle rocks undergo partial melting to generate magma” (Condle, 2015). Volcanism is prominent at two types of plate boundaries, convergent and divergent. At convergent plate boundaries, two plates move towards each other, causing a slab of oceanic crust to descend below the continental plate into the mantle (Subduction), which will create a deep ocean trench. As shown in figure 2.1, this slab of crust drives deeper into the mantle, there will be an increase in temperature and pressure causing the material (water and carbon dioxide) within the slab to reach melting point. After a high enough quantity of the rock has melted, buoyant magma chambers will be formed that will slowly move upwards. If these magma chambers reach the surface of the crust without solidifying, the magma will burst through in the form of a volcanic

However, volcanic eruptions can also impact the atmosphere of earth. When volcanoes erupt, they expose the earth to a wide range of gases and particles that could possible affect the earth’s surface and its climate. “Some of the particles that are released from volcanoes cool the planet by shading the incoming solar radiation” (Centre For Science Education, 2012). Small ash particles generate a heavy and dark cloud in the troposphere, which is the cause of the cooling in the atmosphere. Most of the particles within this dark cloud will fall out of the atmosphere and convert into rain within a few hours. Although, some of the smallest particles travel into the stratosphere, spreading over the earth and cause cooling over large areas for some months.

Volcanoes have also made a contribution towards global warming over the last millions of years. This is due to the amount of carbon dioxide and water vapour that is emitted each time there is an eruption, which negatively impacts the atmosphere. Additionally, volcanoes can shape the landforms around us. They build land far from there original source (vents) through the petrification of the magma and other types of material. The fissure created by the eruption, forms basalts, which can build lava plains that cover hundreds of