Thursday, June 28, 2012

Continental Drift

The movements of the plates in the crust make the continents move in past times continents have been located in other parts of the earth, sometimes far apart, sometimes close together and sometimes even colliding, all as a result of currents in the Mantle. This theory was formed by German climatologist, Alfred wegener in the beginning of this century.
His strongest evidence was that the coastlines of Africa and South America nearly fit together and that the same kind of fossils were found in each. However this theory was not generally accepted until the 1960's. 
1,Permian/Triassic 230 million years ago
2,Jurassic/Cretaceous 140 million years ago
3,Tertiary 65 million years ago
4,Quaternary Present Day
In the Permian and Triassic Era, about 230 million years ago, all the continents moved towards each other and formed a super continent which Wegener named 'Pangaea'. Later by the time of Dinosaurs, about 140 million years ago, the super continent split up into what was to become todays continents. The south Atlantic opened up, While India, Which infact is a continent of its own moved northwards and collided with Asia forming the Himalayas, Australia and the Antartic were attached for a longer time.


Structure of Earth


Built up in layers. The main part of the earth is fluid Mantle, consisting of silicates. In volcanic eruptions this viscous material is recognized as Magma. The core is mainly made up of iron, and despite the higher temperature (about 5000 degree Celsius) it is solid due to the high pressure about 3-5 million atmospheres. The surface layer is called Crust and is only some 5-15 km, 3-9 miles thick. It consists of rigid plates that move because of the currents in the mantle.