Moving Continents

By Chas Parker

Around 200 million years ago, the Earth contained a single land mass named Pangaea. Some 20 million years later Pangaea had split into two pieces, Lauraisa, and Gondwanaland. The former comprised the areas which would eventually become North America, Europe, and most of Asia, whilst the latter comprised the future South America, Africa, Australia, Antarctica and India.

During the course of the following 40-80 million years, India split away from Gondwanaland, moving slowly north to eventually collide with Asia, the resulting force throwing up the Himalayan mountains, and Australia parted company with Antarctica, also by now a separate entity. The continents of 40 million years ago have recognisable shapes, with the ever-widening Atlantic ocean pushing the Americas and Africa and Europe further apart until they assume the positions they occupy today.

The continents are still moving at a few centimetres every year. The Atlantic continues to widen while the Pacific is slowly shrinking. The Mediterranean will eventually close up and it is predicted that in another 60 million years, Australia will have moved north as far as the equator. 

The German meteorologist and polar explorer Alfred Wegener was the first to propose the notion of continental drift in his book, Die Entstehung der Kontinente und Ozeane (The Origin of the Continents and Oceans) published in 1915. Wegener had noticed the similarity between opposing coastlines of the Atlantic ocean as early as 1910 but it was only after reading a report the following year which stated that fossil evidence supported the idea of a land-bridge once uniting Brazil and Africa, that the concept of entire continents moving across the surface of the Earth occurred to him. He proposed that the land masses had once been joined together in the supercontinent Pangaea, which at some time had broken apart, the pieces moving away from one another.

Wegener cited the fact that rock formations found in eastern Brazil matched those in Western Africa in terms of age, type and structure. In addition, the distribution of plants and animals, together with the matching fossils on the two continents, gave strength to his argument.

His ideas were not well-received by geologists and it took until the 1960s before they were fully embraced. By then detailed studies of the residual magnetism contained within rocks, which could pinpoint where on the Earth's surface they had formed, together with the study of plate tectonics which showed that the ocean floors were themselves moving and, in effect, pushing the continents along, proved conclusively that Wegener's theory was correct.