Plate tectonics
Plate tectonics model The theory of which has revolutionized modern geology. A vast amount of scientific evidence supports the central theme of the theory that the earth's outer rock layer (lithosphere) is fractured into large pieces (plates) which move around the globe, carrying overlying oceans and continents with them. The theory has correctly predicted the distribution of earthquakes, volcanoes and mountain chains, greatly improving our understanding of geology. However, not all aspects of the theory are fully explained - the driving force behind plate motion is the subject of several competing hypotheses: . The Convection Cell Model: large convection cells in the earth's partially molten mantle exert a drag on the overlying plates, carrying them along like objects on a giant conveyor belt. Ridge push" and "slab pull" are both ways that gravity can act to keep a plate in motion. Note that arrows on convection cells and overlying plate are going in the same direction. 2. The Push-Pull Model: the creation of new oceanic plate at spreading centers pushes the plates away on either side and, at the same time, colder, denser plate material sinks at subduction zones pulling the plates along behind them. The electromagnetic field applies both pushes and pulls to bodies in the field. This is accomplished via photons and photon "holes" in the field traveling both forward and
Plate Tectonics
Jai Mehta 11AY ) 2) a) Plates "float" or move very slowly (a few mm per year) on the molten material of the mantle. Convection currents in the mantle cause this movement. b) Plates meet at plate boundaries or margins. c) Plates that move apart are known as diverging and are constructive, as new features are formed e.g. submarine volcanoes in the Mid Atlantic plate margin. d) Plates that move towards each other are converging and destructive - Fold Mountains, earthquakes, and volcanoes are common. e) Plates which move sideways against each other are conservative margins - material isn't gained or lost, volcanoes are rare and earthquakes are common e.g. San Andreas Fault. f) Pangaea was a single landmass; made up of all the present continents, believed to have existed between 300 and 200 million years ago the rest of the Earth was covered by the Panthalassa Ocean. Pangaea split into two landmasses Laurasia in the north and Gondwanaland in the south, which subsequently broke up into several continents. These then moved slowly to their present positions, due to plate tectonics. Jai Mehta 11AY 3) A Map Showing The Location Of The Worlds Plate Boundaries. Jai Mehta 11AY 4) Volcanoes can be found where Earthquakes are found, at plate margins/ boundaries. The map below shows a good example of this; you can see where the pacific plate meets surrounding plates and many
Why do LEDC's Suffer Greater Damage From Earthquakes Than MEDC's
Why do LEDC's Suffer Greater Damage From Earthquakes Than MEDC's A MEDC is a more economically developed country; therefore it can afford to spend money on improving the countries stability and helping to decrease the damage from an earthquake. An example of a MEDC is Kobe, in Tokyo, where in January 1995; an earthquake that measured 7.5 on the Richter scale hit the city. A LEDC is a less economically developed country and therefore cannot afford to spend money to protect the country from earthquakes. An example of an LEDC is Armenia, in Columbia, where on the 25th January 1999; an earthquake measuring 6.3 on the Richter scale was the worst earthquake the country had experienced since 1983. As MEDC's have more money to spend on prediction methods, I would expect there to be less deaths and damage in MEDC's than in LEDC's. This is due to a number of reasons. Firstly, because MEDC's are more economically developed, they can afford to spend money on prediction methods, such as GPS satellite, which is when data is sent from satellites to computers with information such as plate movement and changes in the earth's surface. This prediction method is very accurate; however, a disadvantage is that if the computers fail then all of the data will be lost. Also, the fact that MEDC's have more money would also mean that they can spend more money on preparing the country for an
Why did so many people die in the Kobe earthquake?
Why did so many people die in the Kobe earthquake? On the 15th of January 1995 at 5.46am a horrendous earthquake reaching 7.2 on the Richter scale, the worst in half a century struck the large Industrial town of Kobe. Over 5000 people were killed as a result of this earthquake. The tension built up between the Pacific and Eurasian plates and caused the earthquake, as the focus was at such a shallow point, the waves of the earthquake were very powerful. The epicenter was on Awaji Island within 20km of Kobe, so there wasn't enough space between the epicenter and Kobe for the waves to be absorbed. The earthquake first made the ground shake vertically then sideways. Hundreds of shock waves after the earthquake caused most tall buildings to collapse. As one aftershock got to the top of a building then bounced down again it would be hit by another aftershock working its way up the building, making the middle of it collapse. Houses collapsed trapping many people in their beds, immediately fires started and burnt out of control, trains were thrown off their tracks, water and gas mains collapsed. It was announced a state of emergency and army troops were sent to help. Very few people died due to the actual earthquake, most people died because of the primary or secondary effects. Primary effects such as damaged buildings or broken water or gas pipes lead to the secondary effects,
