A body of inland water that flows in a natural channel into the sea, a lake, or, as a tributary, into another river. The main sources of rivers are springs, lakes, and glaciers. Near the source a river flows swiftly, the rocks and other abrasive particles eroding a steep-sided V-shaped valley (see erosion). Variations in the hardness of the rocks over which it runs may result in waterfalls. In the middle part of its course the gradients become less steep, and lateral (sideways) erosion becomes more important than downcutting. The valley is broader, the flow less swift, and meandering more common. Toward the river mouth, the flow becomes more sluggish and meandering prominent: the river may form oxbow lakes. Sediment may be deposited to form a delta.
Related entries canyon
Related categories GEOGRAPHY
• GEOLOGY AND PLANETARY SCIENCE
Home • About • Copyright © The Worlds of David Darling • Encyclopedia of Alternative Energy • Contact