THE LAND

France is composed of a number of distinctive natural units, many of which have a complicated geologic history and form a pattern of great variety. The country's landscapes vary from flat, almost featureless plains to Mont Blanc, which spreads across the border of France and Italy, rising to 15,771 feet (4,807 meters) in the glorious French Alps.

Northern France, particularly the region of Ile-de-France and its margins, is dominated by the Paris Basin. This vast surface, which appears very flat in many places, has been compared to a series of saucers of decreasing size stacked one inside the other. There are gently sloping surfaces toward the interior, and steep slopes on the outer edges. Paris is in the center of the basin, and the outward-facing ridges, composed primarily of resistant limestone, have historically provided strong defensive lines to the east. The ridges form rugged chalk cliffs along the English Channel to the west. To the north, the Paris Basin blends into the plains of Flanders and northwestern Europe. The Ardennes and Vosges mountains to the northeast and east are part of a zone extending beyond the Rhine River through central Germany.

To the west, much older rocks, mainly granites and schists, form the Massif Armoricain of Brittany and the Cotentin Peninsula of Normandy. In the southwest, the Paris Basin is connected by a low threshold, called the Gate of Poitou, to the other large lowland region in France, the Aquitaine Basin. Along the Bay of Biscay, Aquitaine has many areas of sandy soil and some of France's flattest surfaces. The south-central part of France is dominated by a large area of uplands, mostly of volcanic origin, known as the Massif Central and including the regions of Limousin and Auvergne. This area is dotted with peaks rising from 4,000 to 6,000 feet (1,200 to 1,800 meters), which impede communications and economic activity.