The Grand Canyon is America's most famous gorge.
Canyons and gorges are some of the earth's most conspicuous features. The 150-mile long Yarlung Zangbo Grand Canyon of China is one of most notable as it bends and slices through the eastern Himalayas. Nepal's Kali Gandaki Gorge is the world's deepest with a difference of 22,310-feet from its highest peak to the Gankaki River's surface. The 6,000 foot deep Grand Canyon is 277 miles long and exposes two billion years worth of rock layers. Mexico's Copper Canyon, or Barranca del Cobre, is comprised of a system of six canyons cut into the Sierra Tarahumara Mountains.
Canyons
Canyons, gorges, ravines and chasms are geological features that cut into the bedrock to form deep rifts in the earth. Canyons exhibit a wide diversity of forms and topography. Given enough time, canyons will eventually erode into expansive valleys. Canyons, even those in arid regions often feature a river at their bottom. The rocky formations of canyons and gorges are some of the most remarkable landforms on the planet and are a testament to the erosive power of water.
Formation
Canyons and gorges are essentially deep cuts in the earth's crust. Running water is the erosive force behind their formation. Rivers carry hard granular rock particles that wear away at the bedrock over long periods of time until a crevice is carved out of the solid rock. Canyons located in the dry American Southwest are subject to flash floods from the heavy runoff of the parched, crusted soil. The rushing waters carry larger rocks that knock loose more of the canyon walls, enlarging the gorge.
Geology
Many canyons occur in uplifted plateaus with elevations of 1,500 feet or more. Plateaus such as the Colorado Plateau are the remnants of eroded mountains that were formed by the uplifting actions of plate tectonics. Water draining off the steep sides of the plateau over millions of years scour channels in the underlying soft sedimentary rock. Variously aged layers of rock erode differently, giving canyons and gorges their distinctive colors and shapes.
Types
Slot canyons are very narrow deep gorges cut into the sandstone of the plateaus. Slot canyons100 to 200 foot deep may be as little as 3 feet across at the surface. They are carved by periodic high-volume flash floods. Box canyons form when a spring at the base of a permeable rock cliff seeps into the stone and leaks out the cliff's sides causing them to collapse. The heads of box canyons are dead ends, with three sides featuring cliffs.
Differences
Most geologists agree that canyons and gorges are essentially the same thing. They are variations of a valley with steep-sided walls and a river flowing through its bottom. To some geologists the difference is a matter of scale; canyons are bigger than gorges. Some geologists define canyons as chasms located on arid plateaus at least 1,500 feet tall. They must have at least one steep-sided wall. The term canyon is used in the United States while Europeans prefer the word gorge.
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