Plate Tectonics

 

Some of the fossils found on more than one continent

In 1912, Alfred Wegener noticed that the shape of South America somewhat matched that of Africa. He thought that these two continents were once joined and were drifting apart. Then, he came out with the concept that all continents were part of a a single one, Pangaea. He backed his idea with the fact that similar animal and plant fossils exist on various continents now separated by vast oceans.

In the 1950’s to 70’s, a more general theory called Plate Tectonics was developed. Yes, it took all that time for scientists to realise that the Earth being finite, if continents are drifting apart on one side, they are bound to bump into each other somewhere on the other side, aren’t they? This is how mountain ranges appear: for example, the Himalayas are the result of the Indian plate moving into the Asian plate (not shown on the picture).

Are we sure the continents are moving? Yes. When I took up my job as geophysics engineer on Macquarie Island, one of the instruments I looked after was a high precision GPS mounted on an ugly concrete post. It could tell where the island was with a 1cm precision. There is a worldwide network of such GPS’s. So we know that all plates are moving. The Australian plate includes Australia, New Zealand, and Macquarie Island among other things. Where is Australia going? ask the politicians. Simple: North-East at about 62mm per year.

Reference:

https://www.livescience.com/37706-what-is-plate-tectonics.html