The theory was proposed by Alfred Wegner in 1912 but it came into light only after 1920. Basically Wegner was a Meteorologist and proposed this theory to explain the climatic changes during pre-historic times.
Also Read: Rejuvenation and Polycyclic Landforms
Evidence in Favour of the Theory
- Zig-Saw fit of far -away Continents and countries - south America and Africa can be refitted again or juxta-positioned.
Jig-saw fitting (juxtaposition) of South America and Africa - Similarly in Geological features at the coastal margins of Atlantic Ocean - The Caledonian and Hercynian mountain at the Western and Eastern coastal margins of Atlantic Ocean. Similarly Applachians in Eastern Coast of North-Eastern region of North America are similar to mountains in Wales, British Isles, Ireland and Western Europe. Note:- Du Toit done a comprehensive research and proved that the geological feature of both the coastal margins of the Atlantic Ocean are very much similar.
Geological Similarity on the Eastern coast of South America and the Western coast of Africa - Fossil Evidences - The Glossopteris flora present at Falkland, S. Africa, Peninsular India, Australia and Antarctica are similar which proves that al these places are united sometimes ago.
- Palaeo climatic Evidences - The Carboniferous Glaciation of Brazil, S. Africa, Falkland, Peninsular India, Australia, Antarctica are of same Carboniferous period. Which proves that all these places were united in Carboniferous period.
- Besides above one important observation is seen in Scandanavia where a small animal, Lemmings are seen to moe towards West their population increased very much but they foundered in Norwegian Sea water because absence of any land. This observation proves that sometimes ago when Angaraland/Lauratia was united these Lemmings used to move towards the West. Greenland is constantly moving at the rate of 20 cm/year Westwards (Geologically proved fact) which also supports the theory.
The Process of the Theory
1. Breaking of Pangaea and it's Movement - According Wegner before Mesozoic Era all present continents were United which is as named as Pangaea and there was a huge Ocean called 'Panthalasa'. According to Wegner the earth is made up of only three types of materials i.e. upper layer is formed of 'SiAl' (Silica and Aluminium) and then second layer ws formed of Silica and Magnesium i.e. 'SiMa' and Third layer was formed of iron and Nickel I.e. 'NiFe'. He considered the surface between SiMa and SiAl frictionless and he further said that the Pangaea broke down in Mid-Mesozoic Era and moved in two directions: -
I. Towards Equator - Under influence of differential gravitational force and force of buoyancy (resultant of both). Lead to formation of Lauratia and Gondwana land.
II. Towards West - Under influence of Tidal forces of Sun and Moon which attracted Lauratia and Gondwanaland Westwards. Leading to breakdown of both and lead to formation of both and lead to formation of two Americas (North and South).
2. Formation of Mountains - The mountain of Rockies and Andes in two Americas were Form,ed due to Westward movement of both continents due to Crumbling and Consequent folding of continental Rocks of Pacific Ocean. Here He mistaken and contradicted.
3. Formation of Island Arcs - These were also formed due to Westward Movement of Pangaea.The Island Arcs such as Japan and Philippines etc did not keep with the Westward Movement of Angara land and hence they were separated .
Similarly West Indies and Antells etc. in Atlantic were formed because of differential rate of West-ward Movement of Americas.
Criticism of the Theory
- If tidal forces were responsible for the Westward Movement than it would must be at least 10,000 million times more powerful than what it is now. Suc a force is not possible because it will stop Earth rotation.
- If gravitational forces and force of Buoyancy (resultant of both) were such powerful to lead to Equator-ward movement than every continent must located near equator and come at one place.
- In initial part of the theory he said that there was friction between 'SiMa' and 'SiAl' but in the later part of his theory he contradicted himself when he say that rockies and Andes were formed due to crumbling of oceanic and Continental Crust.
Conclusion
- Although Wegner's theory was almost rejected by modern Geographers but one can surely say that his theory of Horizontal Movement still has significance, which laid the foundation stone of Plate Tectonics Theory (1960).
- Besides above He can also be appreciated because he was first, who dare to do research and produced a theory on such complex subject matter.