Continents and Ocean Basins | Geography

In this article we will discuss about the introduction and distributional patterns of the continents and ocean basins.

Introduction to Continents and Ocean Basins:

Continents and ocean basins being fundamental relief features of the globe are considered as ‘relief features of the first order’. It is, therefore, desirable to inquire into their mode of possible origin and evolu­tion. Different views, concepts, hypotheses and theo­ries regarding the origin of the continents and ocean basins have been put forth by the scientists from time to time.

Before examining these views about their origin we should know the characteristic features of the distributional patterns and arrangement of the con­tinents and ocean basins as seen at present. About 70.8 per cent of the total surface area of the globe is represented by the oceans whereas remaining 29.2 per cent is represented by the continents.

Even the distri­bution of different continents and oceans in both the hemispheres is not uniform.

Distributional Patterns of the Continents and Ocean Basins:

The following character­istic features of the distributional pattern of the conti­nents and ocean basins may be highlighted:

(1) There is overwhelming dominance of land areas in the northern hemisphere. More than 75 per cent of the total land area of the globe is situated to the north of the equator (i.e., in the northern hemisphere). Contrary to this water bodies dominate in the southern hemisphere.

If we divide the globe in two such hemispheres where the north pole stands located in the English Channel and the south pole near New Zealand, then the northern hemisphere would be ‘land hemi­sphere’ while the southern hemisphere as ‘water hemi­sphere’. Thus, the land hemisphere would represent 83 per cent of the total land area of the globe while the water hemisphere would carry 90.6 per cent of the total oceanic areas of the globe.

(2) Continents are arranged in roughly triangu­lar shape. Most of the continents have their bases (of triangle) in the north while their apices are pointed towards south. If we take North and South Americas together, they represent equilateral triangles, the base of which would be along the arctic sea while the apex would be represented by Cape Horn. If we take these two continents separately, again they form two separate triangles.

Similarly, Eurasia also assumes the form of a triangle the base of which is along the arctic sea while its apex is near East Indies. The base of African triangle is towards north while its apex is the Cape of Good Hope. Australia and Antarctica are the exceptions to this rule.

(3) Roughly, the oceans are also triangular in shape. Contrary to the continents the bases of oceans are in the south while their apices are in the north. The base of the Atlantic Ocean extends between Cape Horn and Cape of Good Hope while its apex is located to the east of Greenland. The base of the Indian Ocean is in the south but its two apices are located in the Bay of Bengal and Arabian Sea. The apex of the Pacific Ocean is near Aleutian Islands while its base lies in the south.

(4) The North Pole is surrounded by oceanic water while south pole is surrounded by land area (of the Antarctic continent).

(5) There is antipodal arrangement (situation) of the continents and oceans. Only 44.6 per cent oceans are situated opposite to oceans and 1.4 per cent of the total land area of the globe is opposite to land area. More than 95 per cent of the total land area is situated diametrically opposite to water bodies.

There are only two cases of exceptions to this general rule i.e.:

(i) Patagonia is situated diametrically opposite to a part of north China, and

(ii) New Zealand is situated opposite to Portugal and Spain (the Iberian Peninsula).

(6) The great Pacific Ocean basin occupies almost one-third of the entire surface area of the globe.

The validity and authenticity of any hypothesis or theory dealing with the origin and evolution of the continents and the ocean basins would be determined in the light of aforesaid characteristics of the distribu­tional pattern of the continents and ocean basins.

The presence of the great Pacific Ocean basin and island arcs and festoons of the Pacific Ocean is teething problem before scientists who venture in the precari­ous field of the postulation of the relevant theory of the origin of the continents and ocean basins.

Keeping the above facts in mind Lowthian Green postulated his ‘Tetrahedral Hypothesis’ to explain the intricate prob­lems of the origin of the continents and oceans and characteristic features of their distributional pattern.

Besides, Lord Kelvin, Sollas, Love etc. have also attempted to explain the origin of the continents and ocean basins but their views are not discussed here because they are based on discarded and obsolete arguments and assumptions.

In fact, all the previous hypotheses and theories dealing with the origin of the continents and ocean basins have faded away after the posulation of plate tectonic theory. We will examine here only the concepts of Lowthian Green, F.B. Taylor, A.G. Wegener and of course plate tectonic theory.