Cut by the Colorado River over the last few million years, the Grand Canyon is miles kilometers long, more than 5, feet 1, meters deep, but only 18 miles 29 kilometers across at its widest yawn. Layers of rock in the Grand Canyon tell much about the Colorado Plateau's formative years: a mountain range built with two-billion-year-old rock and then eroded away; sediments deposited from an ancient sea; more mountains; more erosion; another sea; a burst of volcanic activity; and the birth of a river that has since carved the chasm by washing the layers away.
Each layer erodes differently. Some crumble into slopes, others sheer cliffs. They stack together like a leaning staircase that leads to the river's edge.
A mixture of minerals gives each layer a distinctive hue of yellow, green, or red. And its immense size has been seen by very few. More people have orbited the Earth than have hked the Grand Canyon from end to end.
Other canyons start where a spring sprouts from the base of a cliff. Such cliffs are composed of permeable, or porous, rock. Instead of flowing off the cliff, water seeps down into the rock until it hits an impermeable layer beneath and is forced to leak sideways.
Where the water emerges, the cliff wall is weakened and eventually collapses. A box canyon forms as sections of wall collapse further and further back into the land. The heads of these canyons are marked by cliffs on at least three sides.
Slot canyons are narrow corridors sliced into eroding plateaus by periodic bursts of rushing water. Some measure less than a few feet across but drop several hundred feet to the floor. Submarine canyons are similar to those on land in shape and form, but are cut by currents on the ocean floor.
Many are the mere extension of a river canyon as it dumps into the ocean and flows across the continental shelf. Others are gouged from turbid currents that occasionally plunge to the ocean floor. All rights reserved. This refers to the point at which the river reaches the elevation of the large body of water, such a lake or ocean, into which it drains.
Aided by gravity, a river will downcut or erode its channel deeper and deeper in order to reach the level of its final destination as quickly as possible. The larger the difference in height between the river and its destination, the greater the erosive or cutting force of the river. Rivers erode because they have the ability to pick up sediments loose rock fragments and transport them to a new location.
The size of the material that can be transported depends on the velocity, or speed, of the river. A fast-moving river carries more sediment and larger material than a slow-moving one. As it is carried along, the sediment acts as an abrasive, scouring and eating away at the banks and bed of the river.
The river then picks up this newly eroded material, which, in turn, helps the river cut even deeper into its channel. If a river cuts through resistant rock, such as granite, its channel and the canyon it creates will be narrow and deep. If it cuts through weaker material, such as clay or sandstone, its channel and its accompanying canyon will be wide.
When cutting through soft rock, a river can undercut its banks, removing a soft layer of material while a harder layer remains above, forming an overhang. The overhang continues to grow as material beneath it is eroded away by the river until the overhang can no longer be supported and collapses into the river.
Repeated undercutting can lead to landslides and slumps, creating a V-shaped canyon. The walls of V-shaped canyons, especially those located in arid environments, are further eroded by rain and ice. In areas where there is little plant cover, dry soil and rock fragments are carried away easily as rain washes over the canyon walls into the river below. When water seeps into cracks between the rocks of the canyon walls and freezes in colder weather, it expands, widening the cracks and pushing the rocks apart.
Eventually, the rocks lose their hold and plummet down the canyon wall. On the way down, they often hit and loosen other rocks, creating a rock fall that significantly alters the shape of the canyon. Below the garden the cliff curves deeply inward, forming an overhang that would shelter a house; at this point the water is released from the draw of surface tension and falls free through the air in a misty, wavy spray down to the canyon floor where I stand, as in a fine shower, filling my canteen and soaking myself and drinking all at the same time.
Flash floods erode rocks in similar fashion. On the Colorado Plateau, where slot canyons are primarily found, the dry soil cannot fully absorb. In Bryce Canyon, erosion has shaped colorful layers of limestone, sandstone, and mudstone into thousands of spires, fins, pinnacles, and mazes that are collectively called hoodoos. John Wesley Powell. By the latter part of the nineteenth century, the canyons of the Green and Colorado rivers were among the few remaining unexplored areas on the North American continent.
Legends told of a region of giant waterfalls, vicious whirlpools and rapids, and enormous rock cliffs that offered no escape or refuge from the punishment of the rivers. In , a party of nine men led by John Wesley Powell — ventured into this unknown and seemingly terrifying landscape to survey, map, and study the geology of the plateau and canyon country.
Powell, who had served as a major in the Union Army during the American Civil War — and who had lost an arm at the battle of Shiloh, had a lifelong interest in natural history. Drawn by the glamour and mystery of the American West, he set out to explore not only how the region looked but also how its canyons, plateaus, and mountains had been formed.
On May 24, , Powell and his men set off on a river descent of nearly nine hundred miles with no real idea of what terrors and adventures lay before them. Their small vessels plunged through turbulent rapids, foaming waterfalls, and towering canyon walls. Two boats were lost, one member of the team deserted early, and three other members were killed by Native Americans as they gave up on the river journey and attempted to climb out of the Grand Canyon. Despite these hardships, Powell and his remaining men explored the entire reach of the Colorado River, including the Grand Canyon.
They were on the river for ninety-two days. After this epic journey, Powell undertook additional Western adventures, exploring the plateaus of Utah, the Colorado Plateau, and Zion and Bryce canyons. Through his expeditions, he developed the geological idea that the vast processes of uplift and erosion were responsible for the topography or physical features of the canyon and plateau country. In he published these findings and ideas in Canyons of the Colorado.
Rushing across the sloping landscape in a torrent, the flash flood picks up stones and other debris. Finding cracks in the sandstone on the plateau floor, the debris-laden flood acts like an abrasive, scouring away the relatively soft rock grain by grain. Over millions of years, flash floods and wind have dug deeper and deeper into the sandstone, sculpting the floors and spiraling walls of these unique underground canyons. Discovered in by a twelve-year-old girl, Antelope Canyon also known as Corkscrew Canyon lies just outside Page, Arizona, on land owned by the Navajo Nation.
Over hundreds of thousands of years, infrequent but often violent water flows have carved the delicate curves and hollows of this slot canyon from hairline cracks in the sandstone. Noted for its photographic beauty, the canyon changes color from violet to red to orange to yellow as light from the Sun filters in from above, illuminating its sculpted sandy walls.
The canyon, a series of passageways of varying widths and heights, is divided into an upper and lower section. The entire canyon measures 5 miles 8 kilometers in length, and in places it is no more than a few feet wide. Walls of the canyon often rise to a height of feet In August , a severe thunderstorm hit the plateau area around Page, Arizona, dropping a vast amount of water in a short period of time. Since the dry soil in the area could not absorb that amount of water, a flash flood quickly developed and raced toward the normally dry canyon, which was 2, feet meters below the height of the plateau.
A group of twelve tourists were trapped in the lower section of the canyon as an foot 3. Only one person survived the deluge.
At more than 11, feet 3, meters , it descends to a depth almost twice that of Arizona's Grand Canyon. The canyon developed from a fault that has been eroded for millions of years by the Colca River, which runs more than miles kilometers along the Peruvian coast. Looming high in the background of the canyon are snow-capped volcanoes that stand more than 16, feet 5, meters in height. The Inca, the native people who flourished in the area from the twelfth century to the mid-sixteenth century, had carved vaults into the.
Upper Antelope Canyon, a slot canyon near the town of Page, Arizona. Colca Canyon, in Peru, is one of the deepest canyons in the world at a depth of more than 11, feet—more than twice as deep as the Grand Canyon. Unlike the Grand Canyon, parts of Colca Canyon are habitable, with terraced fields supporting agriculture and human life. The Inca word for these sealed vaults, colcas, gives the canyon its present name. Other Incan artifacts in the canyon include ancient tombs perched high on the vertical canyon walls and terraces, flat and relatively narrow strips of ground constructed on the sloping sides of the canyon in order to grow crops.
The Grand Canyon, perhaps the world's most famous canyon, lies at the northwestern edge of Arizona near its borders with Utah and Nevada. Carved by the power of the Colorado River, the canyon stretches for miles kilometers. The Colorado River itself is much longer than the canyon, flowing 1, miles 2, kilometers from the Rocky Mountains in Colorado to the Gulf of California in Mexico. The canyon's depth and width vary.
The maximum depth in the canyon is roughly 6, feet 1, kilometers. Along its South Rim, the average depth from the rim to the river at its bottom is about 5, feet 1, meters. At its narrowest part, the Grand Canyon is less than 1 mile 1. At its widest, it is 18 miles 29 kilometers. On average, the width of the canyon from rim to rim is 10 miles 16 kilometers.
While the Colorado River was the main source behind its creation, present-day precipitation continues to shape it. The area of the canyon that receives the most precipitation, either in the form of snow or rain, is the South Rim, which receives 15 inches 38 centimeters of precipitation each year. By contrast, the bottom of the canyon receives only 8 inches 20 centimeters. Carved by running streams, the canyon's red sandstone walls are almost vertical, with some rising feet meters.
This makes access to the canyon floor difficult. For this reason, the canyon has served as a protective home for more than two thousand years for many ancient and modern Native American tribes. From about to , the canyon served as a home for the Anasazi. These people, thought to be the ancestors of the modern Pueblo, constructed spectacular dwellings both on the canyon floor and high up the walls on ledges between the sandstone layers. Several hundred different ruins are located in the canyon, ranging from individual small grain storage bins to large housing complexes, including a three-story tower house.
On the rock walls throughout the canyon are numerous petroglyphs rock carvings and pictographs rock paintings dating from this period. Perhaps because of drought, perhaps because of other, mysterious reasons, the Anasazi abandoned their cliff dwellings after about and scattered throughout the American Southwest.
In the years after, various Native American tribes inhabited the canyon, including the Navajo, who continue to live and farm on the canyon floor.
What makes the Grand Canyon unique are the different rock layers that form its varying slopes and cliffs. Although found elsewhere around the world, the layers are not found in such great variety and with such clear exposure.
The canyon is a mere five to six million years old, but the rocks exposed in its walls reveal a more complex history. This word is fitting as it matches how canyons are often formed by the movement of running rivers going through them. This water flow erodes and cuts deep into the river bed over many years to create the canyons that we recognize today.
Canyons are also sometimes called gorges , though this term more accurately refers to smaller, narrower, and steeper valleys of similar appearance. There are several ways that canyons can be formed. Swift streams of water that run through rocks are the most common cause of the largest and most famous cliff valleys. Typically this occurs in arid , meaning dry, or semiarid lands where rivers are fed by rain and melting snow transferred from wetter regions upstream.
Canyons are more common in these dry areas because physical weathering typically has a more localized effect in arid areas.
Canyon walls then form in their steep and angular way because compared to their centers they do not get as much of the frequent and large amounts of water flowing through and thus are not nearly as worn and softened. Basically, the water pressure of the river digs deep into the surface below it, while simultaneously carrying away the sediments further downstream, to create the distinctive deep and narrow channels so characteristic of canyons.
The rock layers are worn away until they reach an elevation that matches that of the area where the water drains, meaning canyons typically crop up when the river's headwaters and estuary, meaning a partially enclosed body of water with access to the sea, are at significantly different heights allowing for the pressure to push the river bed down further and further.
An example of a river formed canyon is the Tibetan Yarlung Zangbo Grand Canyon , located in southwestern China and created over millions of years by the Yarlung Zangbo River. This canyon is even deeper than the Grand Canyon, diving down 17, feet and stretching as long as miles. Canyons can both have water in them or be completely dry. Canyons can also be formed as rifts between two mountain peaks, like those in ranges across the Rocky Mountains , Alps, and the Himalayas.
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