An ocean of sand

You would never imagine being able to find fish skeletons in the Sahara desert, in Africa. But scientists have found them.

Many years ago, the Sahara desert must have been an ocean of water. If this is true, the fish bones were left there when the water dried up. But before this happened, it is likely that, where today there is nothing but desert, there would be an immense and fertile plain with rivers and meadows.

The engravings that have been found in the desert caves represent animals that could not have lived in a desert.

After a long time, plants and rivers dried up and the world's largest desert was formed.