1. Mountains

Since the dawn of geological time, no less than nine orogenic or mountain building movements have taken place, folding and fracturing the earth's crust. Some of them occurred in Pre- Cambrian times about 600-3,500 million years ago. The three more recent orogenies are the Caledonian, Hercynian and Alpine. The Caledonian about 320million years ago raised the mountains of Scandinavia and Scotland, and is represented in North America. These ancient mountains have been worn down and no longer exhibit the striking forms that they must once have had.

In a later period, during the Hercynian earth movements, about 240 million years ago, were formed such ranges as the Ural Mountains, the Pennines and Welsh Highlands in Britain, the Harz Mountains in Germany and the Appalachians in America. These mountains have also been reduced in size by the various sculpturing forces.

The last of the major orogenic movements of the earth, the Alpine, occurred about 30 million years ago. Young fold mountain ranges were formed on a gigantic scale. Being the most recently formed, these ranges, such as the Alps, Himalayas, Andes and Rockies are the loftiest and the most imposing. Their peaks are sometimes several miles high.