Continental Drift

Continental Drift

Were the continents of this planet always situated the way they are today? Could there have been one supercontinent that over time broke off into the continents we know now? Merriam-Webster Dictionary defines Pangaea as a hypothetical land area believed to have once connected the landmasses of the southern hemisphere with those of the northern hemisphere (Definition of Pangaea). This theory, discovered by Alfred Wegener, was known as the drift theory. Wegener used the fit of the continents, the distribution of fossils, a similar sequence of rocks at numerous locations, ancient climates, and the apparent wandering of the Earth's Polar Regions to support his idea (Evidence Supporting Continental Drift).

In 1912 Wegener first proposed the theory of continental drift, which states that parts of the Earth's crust slowly drift atop a liquid core. He believed that over 200 million years ago the continents had formed a single mass, which he named Pangaea, meaning "all the Earth" in Greek. That massive continent first broke into two large landmasses, Laurasia in the northern hemisphere and Gondwanaland in the southern hemisphere (Continental Drift). They continued to part and eventually formed the continents that are known today. Wegner's theory was partly based on the amazing fit of South America and Africa. Beneath the bulge of Africa, Brazil fits nicely and the coast of North America fits the bulge of Africa. When pieced together, the continents resembled a giant jigsaw puzzle. Wegner also studied the distribution of major geological bodies, such as rocks, continental crust, and mineral deposits. He found patterns amongst the same type of rocks in the continents of Africa and South America. The distinctive rock strata of the Karoo system in South Africa, which consists of layers of sandstone, shale and clay laced with seams of coal, were identical to those of the Santa Catarina system in Brazil (An Introduction to Plate Tectonics). Another factor to support his theory was the glaciers. Wegener was aware that a continental ice sheet covered parts of South America, southern Africa, India, and southern Australia about 300 million years ago. Glacial striations on rocks show that glaciers moved from Africa toward the Atlantic Ocean and from the Atlantic Ocean onto South America. Such glaciations are most likely if the Atlantic Ocean was missing and the continents joined (Evidence Supporting Continental Drift). Wegener's most compelling argument was that the same types of plants and fossils were found on the coastlines of South America and Africa. This finding indicates that this life form must have evolved on the same single land mass. These two continents are separated by the Atlantic Ocean, which would have made it physically impossible for these creatures to have swum or been moved across the wide area of water.

...