Continental Drift

Continental Drift

Continental drift is the breakup and movement of the Earth's continents relative to each other by drifting across the Earth's surface. Since the initial continental drift hypothesis was proposed, the study of plate tectonics has helped us understand why continents move.

Plate tectonics is the study of the folding and faulting of the Earth's crust (lithosphere).

Biogeography is the branch of biology focusing on the geographical distribution of plants and animals. It has been instrumental in developing our understanding of the evidence for continental drift.

Evidence for continental drift

There is considerable evidence for the theory of continental drift that draws upon fossil evidence, plate tectonics theory and studies of glacier sediments. For example:

• Similar plant and animal fossils have been found on different continents' shores, suggesting that these were once joined. For example:
  1. The Mesosaurus found in Brazil and South Africa.
  2. The Lystrosaurus from rocks of the same age found in South Africa, South America, India, Australia and Antarctica
  3. Earthworms found in South America and Africa suggest that these existed in a common habitat on a single continent.
• The complementary shapes of South America and Africa have enabled scientists to propose how these continents pulled apart due to various plate tectonic forces.
• The study of glaciers left over from the ice ages has provided an important line of evidence for continental drift. Glacial sediments from South America, Africa, India, Madagascar, Arabia, India, Antarctica and Australia showed evidence of having once been joined together, suggesting the existence of the supercontinent Gondwana.

Using this evidence, scientists have inferred that in the past the Earth existed as a super-continent known as Pangea until the early Mesozoic era. There were three major phases in the break-up of Pangea:

• First phase: about \(\text{175}\) million years ago, Pangea began to rift, giving rise to the supercontinents Laurasia and Gondwana.
• Second phase: began in the early Cretaceous period (\(\text{150}\)–\(\text{140}\) million years ago) when Gondwana broke and separated into multiple continents: Africa, South America, India, Antarctica and Australia.
• Third phase: occurred in the early Cenozoic era. During this phase, Laurasia split when North America/Greenland split from Eurasia resulting in the expansion of the Atlantic and Indian Oceans.

Diagram showing continental drift.