Geology of Grand Canyon National Park - Geologic Wonders

Grand Canyon National Park

Grand Canyon National Park


Hailed as one of the Seven Wonders of the World, the Grand Canyon exhibits the largest section of geologic time on earth. Hiking to the bottom, one passes through a third of the planet's age. The Park also contains excellent exposure of the world renowned Great Unconformity, an impressive angular unconformity, occupying 1.2 billion years in the rock record. The gap in the rock record straddles the Precambrian - Cambrian boundary and is found nearly everywhere around the globe.

Somehow "Grand" does not tell how truly incomprehensible this canyon is. Most people use such words as "marvelous", "stupendous", or "fantastic", but no word is really adequate to describe this amazing creation of nature. The scene continually changes as light plays off the rocks and clouds, creating shadows and contrasts. The world seems larger here with sunrises, sunsets, and storms taking on an added dimension to match the landscape. The permutations are unceasing, and the moods are without end. This is a land to humble the soul.

The Geologic Story at Grand Canyon

Grand Canyon attracts the attention of the world for many reasons, but perhaps its greatest significance lies in the geologic record that is so beautifully preserved and exposed here. The rocks at Grand Canyon are not inherently unique; similar rocks are found throughout the world. What is unique about the geologic record at Grand Canyon is the great variety of rocks present, the clarity with which they're exposed, and the complex geologic story they tell.

There are really two separate geologic stories at Grand Canyon:

The older story is the one revealed in the thick sequence of rocks exposed in the walls of the Canyon. These rocks provide a remarkable (but incomplete) record of the Paleozoic Era (550-250 million years ago), as well as scattered remnants of Precambrian rocks as old as 2000 million years. The story these rocks tell is far older than the canyon itself. Mesozoic and Cenozoic rocks (250 million years old to the present) are largely missing at Grand Canyon (they've either been worn away or were never deposited).


The second geologic story at Grand Canyon concerns the origin of the canyon itself:

When and how did it come to be?

On one level the answer is simple: Grand Canyon is an erosional feature that owes its existence to the Colorado River (which is largely responsible for the depth of the canyon).

Of equal importance are the forces of erosion that have shaped it and continue to shape it today mainly running water from rain, snowmelt, and tributary streams which enter the canyon throughout its length.

The climate at Grand Canyon is classified as semi-arid (the South Rim receives 15 inches (38 cm) of precipitation each year; only 8 inches (20 cm) each year reach the canyon bottom). But what rain received comes suddenly in violent storms, particularly in the late summer of each year, and the power of erosion is therefore more evident here than in places which receive more rain.

How old is the canyon itself?

The early history and evolution of the Colorado River (of which Grand Canyon is only a part) is the most complex aspect of Grand Canyon geology and far beyond our scope here. We do know, however, that the erosion which has shaped the canyon has occurred only in the past five to six million years only yesterday, considering the age of the rocks through which the Canyon is carved.

Grand Canyon continues to grow and change. As long as rain and snow continue to fall in northern Arizona, the forces of erosion will continue to shape the Grand Canyon of the Colorado River.

Why does it look the way it does?

Grand Canyon owes its distinctive shape to the fact that the different rock layers in the canyon walls each respond to erosion in different ways:

  • some form slopes,
  • some form cliffs,
  • some erode more quickly than others.

The vivid colors of many of these layers are due mainly to small amounts of various minerals, most containing iron, which impart subtle shades of red, yellow, or green to the canyon walls. Climate plays an important role, too. If the climate at Grand Canyon were wetter, the planes and trees that grow there would be very different, and the canyon walls might be covered with lush vegetation.

Where Is It?

Grand Canyon is in the northwest corner of Arizona, close to the borders of Utah and Nevada. The Colorado River, which flows through the canyon, drains water from seven states, but the feature we know as Grand Canyon is entirely in Arizona. Most of Grand Canyon lies within Grand Canyon National Park and is managed by the National Park Service. Adjacent lands are administered by:

  • other units of the National Park Service (Lake Mead National Recreation Area and Glen Canyon National Recreation Area),
  • other federal agencies (the Bureau of Land Management and the U.S. Forest Service) or
  • neighboring Indian tribes (the Havasupai, Hualapai, and Navajo Indian Reservations, which border the park to the south and east).

Grand Canyon

Are the Oldest rocks in the world exposed at Grand Canyon? No.

Although the oldest rocks at Grand Canyon (2 billion years old; ie. 2,000,000,000) are fairly old by any standard, the oldest rocks in the world are closer to 4 billion years old. The oldest exposed rocks in North America (which are among the oldest rocks in the world) are in northern Canada.

How Old is the Canyon?

That's a tricky question. Although rocks exposed in the walls of the canyon are geologically old, the Canyon itself is a fairly young feature. The oldest rocks at the canyon bottom are close to 2 billion years old. The Canyon itself an erosional feature has formed only in the past five or six million years (6,000,000). Geologically speaking, Grand Canyon is very young.

How Big is It?

That depends on how you look at it. The park includes over a million acres of land (1,218,375.54 acres; 493,077 hectares, to be exact; or 1,904 square miles; 4931 square kilometers). But most people measure the canyon in river miles, along the course of the Colorado River at the bottom of the canyon. By that standard, Grand Canyon is 277 miles (446 km) long. It begins at Lees Ferry (mile 0)-and ends at the Grand Wash Cliffs (mile 277 (km 446).

The Colorado River is longer, of course (1450 miles (2333 km) long ) from the Rocky Mountains of Colorado to the Gulf of California in Mexico. Grand Canyon is only one of many beautiful canyons which the river has carved. Others include Cataract Canyon and Glen Canyon the latter now beneath the waters of Lake Powell. Most people agree, however, that Grand Canyon is the most spectacular: there's simply no other place in the world that looks quite like it.

Width and depth of the Canyon vary from place to place. At the South Rim, near Grand Canyon Village, it's a vertical mile (about 5000 feet/1524 m) from rim to river (7 miles/11.3 km by trails if you're walking). At its deepest, it is 6000 vertical feet (1829 m ) from rim to river. The width of the Canyon at Grand Canyon Village is 10 miles (16 km) (rim to rim), though in places it is as much as 18 miles (29 km) wide.

Here's another way to look at size: a trip to the bottom of the Canyon and back (on foot or by mule) is a two-day journey. Rim-to-rim hikers generally take three days one-way to get from the North Rim to the South Rim. A trip through Grand Canyon by raft can take two weeks or longer, and experienced backpackers have spent weeks in the more remote areas of the Canyon.

Are there dams in Grand Canyon?

No, although several dams bordering the park have a profound effect on Grand Canyon. At the upper end of the Canyon, 15 river miles (24 km) above Lees Ferry, is Lake Powell, formed by the waters behind Glen Canyon Dam. At the lower end of the canyon is Lake Mead, formed by the waters behind Hoover Dam.

The controlled release of water from Glen Canyon Dam at the upstream end affects the water that flows through Grand Canyon. Waters from Lake Mead flood the lower 40 miles (64 km) of Grand Canyon when the lake is full. Hoover Dam was completed in 1936. Glen Canyon Dam was completed in 1963.

How does one see the canyon?

Nearly five million people see Grand Canyon each year. Most of them see it from their car at overlooks along the South Rim (this includes Grand Canyon Village, Hermits Rest, and Desert View). The South Rim - 60 miles (97 km) north of Williams and 80 miles (129 km) northwest of Flagstaff, Arizona is the most accessible part of the park and is open all year.

A much smaller number of people see the Canyon from the North Rim, which lies just 10 miles (16 km) (as the raven flies) directly across the Canyon from the South Rim. The North Rim rises a thousand feet higher than the South Rim, and is much less accessible. Heavy snows close the North Rim from late October to mid May of each year. Even in good weather it's harder to get to: it's 220 miles (354 km) by car from the South Rim, or 21 miles (34 km) by foot across the Canyon by way of the North and South Kaibab Trails.

The inner canyon includes everything below the rim and is seen mainly by hikers, mule riders, or river runners. There are many opportunities here for adventurous and hardy persons who want to backpack, ride a mule to Phantom Ranch, or take a river trip through the Canyon on the Colorado River (which can take anywhere from a few days to three weeks-there are no one-day river trips through Grand Canyon).

How do people get across the canyon? If you're walking, the South Kaibab Trail crosses the Colorado River on a narrow footbridge 70 feet (21 m) above the water. There is only one way to cross by automobile, and that is via Navajo Bridge, just a few miles downstream from Lees Ferry, where the Canyon is still only 400 feet (122 m) wide.

When and Why did Grand Canyon become a National Park?

Grand Canyon is unmatched throughout the world in the incomparable vistas it offers to visitors on the rim. It is not the deepest canyon in the world (both the Barranca del Cobre in northern Mexico and Hell's Canyon in Idaho are deeper, just to name two), but- the Grand Canyon is known throughout the world for its overwhelming size and its intricate and colorful landscape. Geologically it is significant because of the thick sequence of ancient rocks that are beautifully preserved and exposed in the walls of the canyon. These rock layers record much of the early geologic history of the North American continent. Finally, it is one of the most spectacular examples of erosion in the world.

The history of the Grand Canyon region is just as interesting. Grand Canyon was largely unknown until after the Civil War. In 1869, Major John Wesley Powell, a one-armed Civil War veteran with a thirst for science and adventure, made a pioneering journey through the Canyon on the Colorado River. He accomplished this with nine men in four small wooden boats (only six men completed the journey). His party was as far as we know, the first ever to make such a trip.

In the late 19th Century there was interest in the region because of its promise of mineral resources (mainly copper and asbestos, as it turned out). The first pioneer settlements along the rim came in the 1880s. Early residents soon discovered that tourism was destined to be more profitable then mining, and by the turn of the century Grand Canyon was a well-known tourist destination. Many of the early tourist accommodations were not so different from the mining camps from which they developed, and most visitors made the grueling trip from nearby towns to the South Rim by stagecoach.

In 1901 the railroad was extended from Williams, Arizona to the South Rim, and the development of formal tourist facilities at the South Rim increased dramatically. By 1905 the El Tovar Hotel stood where it does today, a world class hotel on the canyon's edge. The Fred Harvey Company, known throughout the west for hospitality and fine food, continued to develop facilities at Grand Canyon (including Phantom Ranch, built in the inner canyon in 1922). Although first afforded Federal protection in 1893 as a Forest Reserve and later as a National Monument, Grand Canyon did not achieve national park status until 1919, three years after the creation of the National Park Service. Today Grand Canyon National Park receives close to five million visitors each year a far cry from the annual visitation of 44,173 which the park received in 1919.

Grand Canyon became a national park in order to give it the best protection we, as a nation, have to offer. The mission of the National Park Service, here and elsewhere, is to preserve the park and all of its features, including the processes that created them, and to provide for it's enjoyment by park visitors in a way that will leave the canyon unspoiled for future generations. Now, more than ever, we recognize how complex and difficult a task that can be.

Environmental Issues Facing Park Managers at Grand Canyon

Environmental issues of concern to park managers at Grand Canyon are as diverse as the park itself and include air quality, fire management, the impact of increased visitation and endangered species, to name just a few. We tend to think of national parks as islands in time and space, but that's a dangerous illusion: more and more the forces which affect the integrity of the park ecosystem come from outside the park and are beyond the direct control of park managers.

The issue of air quality at the Canyon is a prime example. Many summer visitors to Grand Canyon find the view from the rim obscured by regional haze carried in from urban and industrial areas to the south, and west, from far outside the park. Even in winter, when prevailing winds tend to carry cleaner air from the north, emissions of sulfur dioxide from local sources can significantly impair visibility at Grand Canyon.

Water is another significant issue: most of the water which finds its way into the Canyon comes from outside the park, and the flow of the Colorado River through Grand Canyon is directly controlled by the rouse of water from Glen Canyon Dam, just 15 miles (24 km) upstream from the park. In the past few years a great deal of research has been directed at the effect of Glen Canyon Dam on the Colorado River in Grand Canyon. For years we've been aware of the more obvious effects of the dam: colder water, carefully controlled flows, the absence of distinct seasonal fluctuations, and greatly decreased sediment load. Only now are we beginning to understand the long term effects these changes have had on the system as a whole.

Such issues are of interest to all of us, and there are no easy answers. But the task of preservation and protection within park boundaries is not nearly as simple as it must have looked 75 years ago. The issues which interest park managers are in many cases the same issues which affect us all and which we as a nation must address.

AirFlex Stealth Body Protector...
Price subject to change | Available through
Featured Park
Two deserts, two large ecosystems whose characteristics are determined primarily by elevation, come together at Joshua Tree National Park. The Colorado Desert encompasses the eastern part of the park and features natural gardens of creosote bush...
Featured Wildlife
Maine ocean islands provide the only nesting sites for Atlantic puffins in the United States. Eastern Egg Rock in the midcoast region, Seal Island and Matinicus Rock at the mouth of Penobscot Bay, and Machias Seal Island and Petit Manan Island off the downeast coast provide habitat for more than 4,000 puffins each summer.