Rivers form most gorges.
A gorge is a narrow valley that lies between rocky walls, glaciers, hills or mountains. Gorges are a certain type of canyon, and they belong to the larger category of valleys, which are depressions on the earth's surface. The Grand Canyon, although its name would suggest otherwise, is actually one of the most famous gorges in the United States.
Formation in Rock
Gorges in rock formations are the result of sediment movement in rivers. Over time, rivers pick up small bits of rock, shells, dead plants and other particles, and transport them down the river. This leads to the gradual erosion of the material on a riverbed. It takes thousands of years for this gradual erosion to cause massive crevices in the earth; those crevices are gorges.
Formation in Ice
Gorges that form in glaciers have a slightly different pattern than those of rock formations. Glaciers typically have fluffy ice at the top and firm ice at the bottom. In between is a layer called firn, which is where the water and ice in glaciers move from the top to the bottom. The firn develops avenues that easily transport ice, which are essentially icy rivers. These icy rivers erode certain parts of the glacier, causing massive cracks in the ice over time; those cracks are gorges.
Gorges and Canyons
A valley is a broad term that describes any low area that has two higher areas surrounding it. A canyon, which is also a valley, is a V-shaped crevice that forms by erosion from a river or stream. A gorge is a particularly deep and narrow canyon that usually has rocky walls, although the walls may also consist of ice in glaciers. Particularly wide or gradually inclined valleys might be called canyons, but they wouldn't be narrow or steep enough to qualify as gorges.
Dams
Because gorges are very steep and usually have fast-running water at their base, they offer the opportunity to harness a lot of power via dams. However, many question the ecological impact of these dams on the local environment. The Three Gorges Dam in China, for example, has been highly criticized for its rapid and hasty development, which flooded numerous homes of people and animals in the local area during its construction.
Tags: gorge, gradual erosion, rock formations, rocky walls
