Plant Science Portal 
Continental Drift

At one time, all of the world's continents were joined into one super-continent called Pangaea. Pangaea later broke-up to become two major continents; Laurasia and Gondwana. (Refer to maps).

Laurasia was composed of Europe, North America and Asia, while Gondwana was composed of Africa, South America, New Zealand, Madagascar, India, Antarctica, Arabia, Iran and Australia.

There is strong supporting evidence in favour of the theory of continental drift. Such evidence includes similarities in rock types, fossils, flora and fauna of previously-joined continents.

India provides a good illustrative example of the continental drift theory. In paleontological terms, India is considered a "southern land mass" and is often referred to as "the sub-continent". India broke away from Antarctica and Africa about 100 million years ago, yet the flora in India today is more closely related to the flora of Africa than that of Asia, to which it is currently joined. India is slowly pushing into Asia (hence the Himalayas which are still rising to this day) but in botanical terms is not actually a part of Asia at all! Of course, India has been joined to Asia for several million years now, so understandably some Asian flora has since colonised the Indian subcontinent.

As well as modern flora today, there is ample supporting evidence of the theory of continental drift in the fossil record. The presence of plants from the order Glossopterid in the fossil records of Australia, Antarctica, India, Africa and South America suggest that these continents were joined at one time. Glossopterid fossils have never been found in Asia. There are other fossil species shared across the southern land masses including Deucridium spp, and a range of reptiles, amphibia and fish.
Kilauea volcano lava flow spitting into the air
Kilauea volcano, Hawaii. Photo by "slworking2", used under a Creative Commons licence.
How do the continents move?

The earth's crust consists of at least fifteen plates. These are made of rigid lithosphere and carry the world's continents. When the edges of these plates collide, earthquakes and/or volcanoes can result as lava rises to the surface or pressure is released from stresses between the continental plates. (Tsunamis are sometimes a bi-product of these processes).

One of the reasons why there are no earthquakes or live volcanoes in Australia is because Australia lies within the middle of the Indian-Australian plate. Countries or regions that lie on the areas where the plates meet are often subjected to these phenomena, examples being New Zealand which has lots of volcanoes due to its location on the Indian-Australian and Pacific Plates, and the west coast of the United States, which lies on the join of the Pacific and American plates. Japan is another country which historically has been subjected to earthquakes and volcanoes.

While the plates are moving, the continents are drifting also.

India is pushing so hard into Asia and is being forced underneath the Asian continent. As a result, the height of the Himalayas is rising every year. Australia is also moving north, albeit at a much slower 6 cm a year. In the last 45 million years, Australia has moved through 27° of latitude. In another 20 million years, Cape York will have reached the equator!
Contact

Contact Adam Dimech

To contact me, please use the

Feedback Form

or send a message via the following social media:


Facebook Flickr GooglePlus Twitter