Very early in Earth's history, Greenland and the north of Europe must have been connected by a land bridge. A similar link joined Spain and North America. Southern America, Africa and Australia were in one block. Later on pieces of land broke off and floated away. Today thousands of miles of sea are between them.

During part of the Ice Age, the British Isles and the point of southern Sweden were joined to the European and continent. The North Sea? The English Channel? Enormous marshes! The Rhine flowed from Switzerland, with the River Thames as a tributary! This enormous river still exists in the North Sea and is called the Silver Deep'.

At the same time, Siberia was probably linked to Alaska by a stretch of land over the Bering Straits. Asian prehistoric man traveled this way, as did animals. Mammoth traveled between Asia and America over this bridge.