Alfred Wegner was a German Meteorologist in the early 1900s who studied ancient climates. Like most people, the jigsaw puzzle appearance of the Atlantic continental margins caught his attention. He put together the evidence of ancient glaciations and the distribution of fossil to formulate a theory that the continents have moved over the surface of the Earth, sometimes forming large supercontinents and other times forming separate continental masses. He proposed that prior to about 200 million years ago all of the continents formed one large land mass that he called Pangea .
According to Alfred Wegener, the entire landmass of the globe was together about 280 million years ago. It was termed as Pangea, a super continent. The huge water body surrounding the Pangea was known as Panthalasa. From 80 to 150 million years ago, Pangea was broken latitudinally into northern and southern parts known as Laurasia (Angaraland) and Gondwanaland, respectively. Both of them drifted away and in between a shallow sea emerged by filling up the water from Panthalasa. It was known as Tethys sea. Later on Laurasia and Gondwanaland rifted and finally drifted to form the present day distribution of land and water on the earth .
Wegener’s explanation of continental drift in 1912 was that drifting occurred because of the earth’s rotation. Fossil records from separate continents, particularly on the outskirts of continents show the same species.
The evidence which gave rise to the theory of continental drift includes the following:
- The coasts of the continents surrounding the Atlantic ocean could, if the continents were moved closer, fit together like a jigsaw puzzle.
- Living animals in widely separated lands are similar. For example India and Madagascar have similar mammals, which are quite different from those in Africa, even though it is now near to Madagascar.
- Fossil plants in India, South Africa, Australia, Antarctica and South America are similar to each other. This so-called Glossopteris flora is quite different from plants found in other parts of the world at the same time.
- There are numerous geological similarities between eastern South America and western Africa.
- Apparent Polar Wandering: Paleomagnetism tells us how far from the poles rocks were when they formed, by looking at the angle of their magnetic field. The story told by different continents is contradictory, and can only be explained if we assume the continents have moved over time.There are ridges in the floors of the main oceans.Paleomagnetism shows that the sea floor has spread away from these ridges. Distinct patterns of stripes can be seen in the magnetism of rocks on either side of the ridges.
- BPCS 2020 Mains (65th Mains) Tests and Notes Program
- BPCS Prelims Exam 2020 (66th Prelims)- Test Series and Notes Program
- BPCS Prelims and Mains 2020 Tests Series and Notes Program
- BPCS Detailed Complete Prelims Notes