Continental Drift

The Atlantic Ocean’s coastlines are strikingly symmetrical. Look at the bulge of Brazil and the notch of the Gulf of Guinea on the opposite shore — they seem made for each other. This visual match led many thinkers to suspect that the Americas, Europe, and Africa were once a single landmass. The first person to formally propose this, as far as recorded history goes, was Abraham Ortelius, a Dutch map maker, in 1596. Later, Antonio Pellegrini drew a map showing the three continents joined together. But the idea found its most complete expression in 1912, when Alfred Wegener, a German meteorologist, put forward the continental drift theory to explain the distribution of oceans and continents.

Wegener’s central claim was that all the continents once formed a single continental mass, surrounded by one vast ocean. He named the supercontinent Pangaea, meaning “all earth,” and the mega-ocean Panthalassa, meaning “all water.” Around 200 million years ago, Pangaea began to split. It first broke into two large masses: Laurasia in the north and Gondwanaland in the south. These two then continued to break apart into the smaller continents we see today. Wegener did not stop at the claim — he offered a range of evidence to support it.

Evidence in Support of the Continental Drift

The Matching of Continents (Jig-Saw-Fit)

The shorelines of Africa and South America facing each other show a remarkable and unmistakable match. In 1964, Bullard used a computer programme to find the best fit of the Atlantic margins, and the result proved quite perfect. Importantly, the match was tried at the 1,000-fathom line — the edge of the continental shelf — rather than the present-day shoreline. This deeper contour fits far better than the coastline itself, because shorelines have been altered by erosion and sea-level changes over time.

Rocks of Same Age Across the Oceans

Radiometric dating methods, developed in recent times, made it possible to correlate rock formations across vast oceans. The belt of ancient rocks about 2,000 million years old from the Brazil coast matches with rocks of the same age in western Africa. Further, the earliest marine deposits along the coastlines of South America and Africa are of the Jurassic age. This suggests that the Atlantic Ocean did not exist before that time — the two continents must have been joined until then.

Tillite

Tillite is a sedimentary rock formed from deposits of glaciers. The Gondwana system of sediments in India has counterparts in six different landmasses of the Southern Hemisphere. At its base, this system has thick tillite, indicating extensive and prolonged glaciation. The same succession of rocks is found in Africa, the Falkland Islands, Madagascar, Antarctica, and Australia. The overall resemblance of these Gondwana-type sediments shows that these landmasses had remarkably similar histories. The glacial tillite provides unambiguous evidence of past climates (palaeoclimates) and of the drifting of continents.

Placer Deposits

The Ghana coast has rich placer deposits of gold, yet the source rock is completely absent in the region — an amazing fact. The gold-bearing veins are in Brazil. It is obvious that the Ghana gold deposits were derived from the Brazilian plateau when the two continents lay side by side. The gold was carried and deposited by rivers, and when the continents drifted apart, the deposits were left on opposite shores.

Distribution of Fossils …