Climatology for Kerala PSC: Structure of the Atmosphere May 28, 2022
Climatology for Kerala PSC: Structure of the Atmosphere
- In 1912, Alfred Wegener in a book ‘The Origin of Continents and Oceans’ put forward the idea of lateral movement of continents or continental drift.
- In this theory he claimed that the changes in the appearance of the Earth were largely due to the shifting of continents.
- About 250 million years ago, there was only one super-continent called Pangaea which was surrounded by the super-ocean named Panthalassa.
- About 200 million years ago, the Pangaea began to break up and drift away from one another. One of the parts started floating Northward and another Westward.
- The Northern part was known as Angaraland (Laurasia) and the Southern as Gondwanaland.
- The intervening space between these two giant continental blocks was filled up with a narrow and shallow water body known as Tethys sea.
- Angaraland consisted of present North America and Greenland and Eurasia (without India and Arabia).
- Gondwanaland contained Africa with Arabia attached with South America, Australia, Antarctica and India. South Pole was located near Durban, near Natal in South Africa.
- The Northward movement was caused by gravitational forces, i.e. because of intense gravitational pull of the poles. Whereas the Westward movement was thought to be caused by pull of moon or tidal forces.
- Later on, the further disruption of the Gondwanaland occurred during Jurassic period.
- The Northward movement of Indo-Australian plate and Africa caused the sediments deposited in the Tethys to be crushed and deformed.
- Thus, the Alpine and Himalayan mountain ranges were formed. The Westward movement of America led to the formation of Andes and Rockies and the Caribbean Island arcs.
- It also created opening and widening of Atlantic Ocean.
Evidence of Continental Drift Theory
- The Evidences in support of the theory are
- Jigsaw Fit of continents: It refers to the similarities between the coastlines of South America and Africa, suggest that these were once joined together.
- Structural similarities: The continuity of tectonic trends of the block of these countries across their present boundaries.
- Fossil similarities: The distribution of the fossil plants in Argentina, South Africa, India, Western Australia and Antarctica
- Glacial evidence
- Mountain ranges
- Coal deposits
- Evidence of glacial striation
Criticism of Continental Drift Theory
- The responsible forces for the whole process of the continental drift were not sufficient enough.
- But still the evidences provided by the Continental Drift Theory provided a platform for future work.