Plate Tectonics

Scientists used to believe that mountains and valleys were caused by the the earth’s crust cooling after it was formed. However, one man came along and proposed another theory…

Wegener’s Theory of Continental Drift

alfred wegener

Alfred Wegener was a German scientist who at the beginning of the last century noticed that fossils on either side of the atlantic were actually very similar.

This had been explained away by others by the idea that once South America and Africa had a land bridge between them which animals were able to cross over….and that this had since then been sunk.

Wegener though also noticed that South America and Africa seem to fit together like a jigsaw which led him to believe that perhaps they had once been one piece of land. He dug deeper and found that there are matching layers of rock in each continent. Also he noted that fossils had been found in weird places – for example fossils were discovered in the Arctic where no animals could have lived because it was so cold….so he came up with the idea of CONTINENTAL DRIFT.

Basically his theory states that around about 300 million years go there was only one big continent called Pangaea. This was then broken into bits which form the continents we currently know and these continue to drift today.

pangea1

But nobody believed poor Wegener’s theory and were pretty nasty about it!

The big thing they had a go at was his explanation of how the continents were drifting. Wegener said it was caused by tidal forces and the earth’s rotation and he believed the continents were travelling through the sea bed. This seemed to many to be impossible  and one scientist said such forces would stop the earth rotating (obviously that was wrong!).

Wegener didn’t help himself either as he got his maths wrong and said the drift is happening much more quickly than it actually is.

There may have also been some snobbery as Wegener was an astronomer and not a geologist.

However later when scientist’s had the technology t look out the ocean floor they found evidence he was actually right! Yey for Wegener.

Ten years later everyone was convinced and the current in vogue theory is that the Earth is made up of “tectnoic plates” that move about bumping into each other which pushes up land (and makes mountains).