Drifitng Of Plate Tectonics Flashcards
Discuss the continental drift theory of Wegener.
Professor Alfred Wegener first introduced the drift theory in 1912 and then revised it in 1924. He proclaimed that the climatic changes on such a large scale could possibly only be because of drifting of continents. He was impressed by the jig-saw fit of the eastern and western coastlines of the atlantic ocean and also Australia could easily fit into the Bay of Bengal. Such outstanding similarities in the coastline, especially that of the jig-saw fit by wegener. Considering the above facts wegener gave these theories:-
▪︎ Wegener supposed that several continental landmass were closely aggregated and formed one supercontinent in the upper carboniferous age. The supercontinejt was called Pangea by wegener.
▪︎ pages was surrounded by a vast ocean called the pathalas.
▪︎ The northern part of the Pangea included - north america, Europe and asia and was called Laurasia.
▪︎ The southern part of the pangea included - South America, Africa, Peninsular India, Australia and Antartica and was known as ‘Gondwanaland’ .
▪︎ both laurasia and gondwanaland was seperated by a sea known as the tethys sea.
▪︎ This process started in the upper carboniferous age - 250-300 million years ago.
▪︎ Laurasia and gondwanaland came nearer to each other
▪︎ peninsular india started drifting towards north east.
▪︎ the size of the Tethys sea had become smaller.
▪︎ the sediment deposition in tethys sea suffered golding and himalayas and alps were formed.
▪︎ about 180 million years ago, in the mid jurassic age, atlantic ocean became 100km wide due to westward drift of the America’s.
▪︎ Resulted in the wrinling of their western age and rockies and Andes were formed
What are the three stages of continental drift
1] Upper carboniferous age [300 million years ago]
2] Eocene [ 50 million years ago]
3] early quaternary [1 million years ago]
Define sea floor spreading
The ridges down the middle of the ocean floors have been emitting lava actively. These mid oceanic ridges are Cracks on the floor of the ocean where molten rocks rush up to form new crust. The crust spreads away from the ridge and the ocean basin widens. This phenomenon is known as sea floor spreading.
