Continental Drift

Introduction and Cause Of

Continental drift was a theory proposed in 1912 by Alfred Wegener which determined the movement of continents.  This theory includes part of the plate tectonics idea. The theory demonstrates that tectonic plates have been moving for hundreds of years.

Heat flows from the earths core to its crust and as the asthenosphere is plastic, the lithosphere floats along the convection currents. The idea was originally thought of in North America, but by the 1950's Europe widely accepted the idea. Alfred Wegener also proposed a theory of Pangea (or the supercontinent). This was the only continent, but as time past millions of years later the continents split into their own individual continents: Asia, North America, South America, Africa, Europe, Australasia and Antarctica. South America and Africa are moving 3cm's away from each other each year.

Nowadays there exists lots of evidence for continental drift. The most obvious is the way in which the continents seem to fit jigsaw-like (for example Africa and South America) together when looked at on a map.More scientific evidence comes in the form of plant and animal fossils of the same age found around different continent shores, suggesting that they were once joined.For example the fossils of the freshwater crocodile found in Brazil and South Africa. There is also living evidence - the same animals being found on two continents. One example of this includes an earthworm found in both South and North America. There are two main forms of geological evidence evident: rocks sequences and magnetic stripes. When the rock strata of the tips of separate continents are very similar it suggests that these rocks were formed in the same way implying that they were joined initially. For instance, some parts of Scotland contain rocks very similar to those found in eastern North America. The second piece of evidence arises when the rocks were formed from magma erupting out of a volcano. When this happens the iron particles align with the earth's magnetic field and set in this position. As the earth's magnetic field flips every half-million years, strips of land of alternating magnetic orientation are formed- symmetrical from the volcano. This showed how some plates are moving away from each other.

Comment Stream

2 years ago

A2: well done Alfie. A good understanding and clearly explained. Perhaps some more images to support your text and what will happen to the plates in the future?