Evaluate How Plate Tectonics Theory Helps Our Understanding of the Distribution of Seismic and Volcanic Events
‘Evaluate how plate tectonics theory helps our understanding of the distribution of seismic and volcanic events’
In 1912, Alfred Wegener published his theory that a single super continent named Pangaea once existed about 300 million years ago. He proposed that Pangaea then later split into two continents of Laurasia in the north and Gondwanaland in the south and that today’s continents were the result of further splitting of these two land masses. Where the plates split are known as plate boundaries. Wegener’s theory of continental drift was supported by both geological and biological evidence that these areas were once joined. The geological evidence included the rock sequences in Northern Scotland closely agreeing with those found in East Canada, indicating that they were laid down under the same conditions in one location as well as the obvious jig saw fitting appearance of today’s continents, in particular, the bulge of south America fitting into the indent below west Africa. The biological evidence comprised of fossil findings linking different continents. Fossil brachiopods found in Indian limestones were comparable with similar fossils in Australia and the fossil remains of Mesosaurus’ were found in both South America and southern Africa. It is unlikely that the same reptile could have developed in both areas or that it could have migrated across the Atlantic. Despite the evidence, Wegener’s theory was unable to explain how continental movement had occurred. However from the 1940’s additional evidence accumulated after the discovery of the mid-Atlantic ridge and huge oceanic trenches. Examination of the ocean crust either side of the mid-Atlantic ridge suggested that sea-floor spreading was occurring. Magnetic surveys of the ocean floor in the 1950’s, showed regular patterns of paleomagnetic striping surrounding the ridges. It was discovered that when lava erupts on the ocean floor, magnetic domains within iron rich minerals in the lava are aligned with the
In 1912, Alfred Wegener published his theory that a single super continent named Pangaea once existed about 300 million years ago. He proposed that Pangaea then later split into two continents of Laurasia in the north and Gondwanaland in the south and that today’s continents were the result of further splitting of these two land masses. Where the plates split are known as plate boundaries. Wegener’s theory of continental drift was supported by both geological and biological evidence that these areas were once joined. The geological evidence included the rock sequences in Northern Scotland closely agreeing with those found in East Canada, indicating that they were laid down under the same conditions in one location as well as the obvious jig saw fitting appearance of today’s continents, in particular, the bulge of south America fitting into the indent below west Africa. The biological evidence comprised of fossil findings linking different continents. Fossil brachiopods found in Indian limestones were comparable with similar fossils in Australia and the fossil remains of Mesosaurus’ were found in both South America and southern Africa. It is unlikely that the same reptile could have developed in both areas or that it could have migrated across the Atlantic. Despite the evidence, Wegener’s theory was unable to explain how continental movement had occurred. However from the 1940’s additional evidence accumulated after the discovery of the mid-Atlantic ridge and huge oceanic trenches. Examination of the ocean crust either side of the mid-Atlantic ridge suggested that sea-floor spreading was occurring. Magnetic surveys of the ocean floor in the 1950’s, showed regular patterns of paleomagnetic striping surrounding the ridges. It was discovered that when lava erupts on the ocean floor, magnetic domains within iron rich minerals in the lava are aligned with the