The geography of Norway is dominated by vast mountain ranges broken up by valleys and fjords. Less than 10% of the country's area is arable, and the rest is mountainous. Glaciers are the major cause for erosion, so terrain in Norwegian mountains consists of plateaus and lakes with peaks. These areas have abundant and diverse fauna and flora.
The altitude of the treeline is in reverse proportion to the latitude; in northern Finnmark, treeline is at sea level. The treeline is also lower near the coast and higher on the eastern part of the mountains.
Mountain ranges also form the main boundaries among Norway's districts. They typically run north-south. Several of the ranges have had road and railroad passes since historical times; some are newer; and many close for the winter.
Norwegian mountain ranges provide some of the most attractive recreational areas in Norway, both during the summer and winter. Cabins and trails are operated by the Norwegian Mountain Touring Association at intervals that allow for weeks of uninterrupted hiking or cross-country skiing in the mountains.