CONTINENTAL DRIFT

The theory of continental drift is the earliest way that geologists could explain how the continents moved over time and ‘drifted’ away from each other.

Alfred Wegener: Alfred Wegener was a German polar researcher, geophysicist and

meteorologist.

In 1912, he published a theory showing the idea that around 250 million years ago, one single continent existed which was called the ‘Pangaea’.

His theory concluded that, over time, the continental land masses which once slotted together like a jigsaw puzzle, ‘drifted’ across the earth, also known as the ‘continental drift’.

Wegener’s theory was rejected by scientists as he could not explain a force in which pushed/pulled the continents around the earth. This then lead to him beginning a hunt for evidence to back up his theory.

Evidence: FOSSILS: One piece of evidence which Wegener found was fossils located in

Southern Africa and South America. The fossils were known as the ‘mesosaurus’ which is known for its freshwater habitat. Wegener argued that as the mesosaurus was a freshwater reptile, it wouldn’t have been able to swim across the sea, as the salt water would have killed it. This helps to back up his theory of continental drift.

LANDFORMS: Mountain ranges found in South Africa line up with those found in Argentina which suggests that at one point, they were joined together.

After finding all of the evidence to show that the continents did drift, he unfortunately did not find any evidence showing what the force was that caused the continents to drift in the first place.

He originally thought that, due to the earth rotating, the continents shifted apart during this process. However, scientists were able to prove his hypothesis wrong due to the process of ‘plate tectonics’.

Jack Oliver: Jack Oliver was an American scientist who produced a research

paper in 1968 on plate tectonics, after earning his PhD studying earthquakes and providing seismic evidence for tectonic plates. His research played a vital role in providing evidence for Wegener’s theory of continental drift, which resulted in his theory becoming accepted in the world of science.

Plate Tectonics: As we know today, continents rest on tectonic plates which are

constantly moving around = this process is known as ‘plate tectonics’.

One piece of evidence in which scientists found that support Wegener's idea of continental drift was through the process of ‘sea floor spreading’.

This is where molten rock rises up from within the earth and adds to the original sea floor to create a new one. This is most dynamic along the mid-ocean ridges.

As the sea floor get wider, the continents either side of the ridge begin to move away from each other.

EXAMPLE: The North American and Eurasian plate are separated by the Mid-Atlantic ridge. Both of these continents are drifting away from each other by 2.5 cm each year.

THIS OCCURS AT DIVERGENT PLATE BOUNDARIES.

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