Page 41 - Exercise 2

Page 41 - Exercise 2

Plate tectonics

If you look at a map of the world, you’ll see oceans and continents. Their shapes and positions look permanent, but they aren’t. Look closely at the east coast of 5outh America and the west coast of Africa.

They have a very similar shape. This is because at one time they were part of the same continent. If you had a time machine and you went back 180 million years, you wouldn’t find today’s continents; you would find Just two large continents - Laurasia in the north and Gondwana in the south. Thirty million years before that you would find only one continent - Pangaea.

The continents are part of the Earth’s crust. This is a thin hard layer of rock 5-50 kilometres thick, it consists of several large plates. These plates float on the hot, soft magma below the crust. The heat in the magma makes the plates move. They move very slowly - only a few centimetres a year, but over millions of years, they can travel thousands of kilometres.

Plate tectonics, as this process is called, has produced . the Earth that we see today. When the Indian plate broke away from Gondwana, it moved north and slid under the Eurasian plate. This pushed up the mountains of the Himalayas. The African ptate created the Alps when it crashed into the European plate.

The continents are still moving. Africa is splitting into two parts. The Mediterranean will probably disappear, as the northern part of Africa Joins Europe. If your time machine took you to the future, you would see a very different world from today.