Plate Tectonics #3
Explain the main characteristics of plate tectonic theory?
Leaving Cert Geography
Global plate movement is the study of how the 7 major and 7 minor plates react with each other. Plates are large portions of the earth’s crust that float around the asthenosphere. One process of global plate movement is convection currents. These currents move in a circular motion. Hot magma rises towards the crust where they cool and fall again creating a circular motion. This endogenic or internal force is caused by the radioactive decay of isotopes or elements of rocks.
Continental drift is another process of global plate movement. It was first proposed by Alfred Wegener in 1912, however was only accepted in the 1960’s.He proposed the earth was originally one landmass called Pangaea. It separated into two landmasses known as Laurasia and Gondwanaland which were separated by the Tethys Sea. There are four proofs of continental drift which are as follows.
Continental fit is the theory that the continents look like they could fit together like a jigsaw e.g. South America and Africa look like they could be attached. Secondly mountains in different continents are of the same structure, rock type and age suggesting they may once have been the same mountain range e.g. The Appalachian Mountains, USA and the Caledonian Mountains, Ireland. Planetology is the study of prehistoric life. Fossils found in different continents of animals that couldn’t walk prove that countries must have once been joined together. Glacial deposits in countries such as Africa could not have formed in their equatorial location.
Sea floor spreading proposed by Harry Hess also suggests that plates are spreading to form features such as the Mid Atlantic Ridge. The Mid Atlantic ridge is an underwater mountain range that is 40,000km long.
Describe the causes and effects of an earthquake you have studied
I have studied the January 2010 Haiti earthquake. It occurred at a conservative plate boundary be...