Mountain - geography.

Mountain - geography. I INTRODUCTION Mountain, name usually applied to region of land that is raised rather steeply above the surrounding terrain. Mountains are distinguishable from plateaus by mountains' usually limited summit area (mountains are generally much narrower at the top than at the base) and they are distinguishable from hills by mountains' generally higher elevation. The elevation, or altitude, of a mountain is given as the height of the summit above sea level. Therefore, a mountain with an elevation of 4000 m (13,100 ft) may rise to a level of only 3000 m (9840 ft) above the surrounding land. Mountains are normally found in groups or ranges consisting of peaks, ridges, and intermontane (between mountains) valleys. Except for certain mountains that occur singly, the smallest unit pertaining to mountains is the range, comprising either a single complex ridge or a series of ridges generally alike in origin, age, and form. Several closely related ranges in a parallel alignment or chainlike cluster are known as a mountain system; an elongated series of systems forms a mountain chain; and an extensive complex of ranges, systems, and chains is known as a belt, or cordillera. II FORMATION Geologists believe that most mountains are formed by movements in the earth's crust. The plate tectonics model has helped explain many of these processes. This model describes the crust of the earth as made up of a number of vast plates that move about at the rate of a few centimeters a year leadin...