Grand Canyon

The Grand Canyon is a steep-sided canyon carved by the Colorado River in Arizona, United States. It is 277 miles (446 km) long, up to 18 miles (29 km) wide, and more than a mile (6,093 feet or 1,857 meters) deep. For other Grand Canyons, see Grand Canyon (disambiguation).

The canyon and the land around its rim are protected and shared by several areas. These include Grand Canyon National Park, the Kaibab National Forest, Grand Canyon–Parashant National Monument, the Hualapai Indian Reservation, the Havasupai Indian Reservation, and the Navajo Nation. President Theodore Roosevelt strongly supported protecting the Grand Canyon area and visited it many times to hunt and enjoy the scenery.

Nearly two billion years of Earth's history have been exposed as the Colorado River and its side streams cut their channels through layer after layer of rock, while the Colorado Plateau was uplifted. Geologists still debate some details of how the canyon was formed. However, several recent studies support the idea that the Colorado River found its path through the area about 5 to 6 million years ago. Since then, the river has cut the canyon deeper and wider.

For thousands of years, Native Americans have lived in the area without a break, building settlements within the canyon and its many caves. The Pueblo people considered the Grand Canyon a holy place and made pilgrimages to it. The first European known to have seen the Grand Canyon was García López de Cárdenas from Spain, who arrived in 1540.

Geography

The Grand Canyon is a river valley on the Colorado Plateau. It shows Proterozoic and Paleozoic strata, which are layers of rock that have been pushed upward. It is one of six distinct sections of the Colorado Plateau. The canyon is not the deepest on land, since Kali Gandaki Gorge in Nepal is much deeper. However, the Grand Canyon is known for its huge size and colorful scenery. Its thick ancient rock layers, which are well preserved in the canyon walls, record much of the early history of the North American continent. Mountain-forming uplift later raised these layers thousands of feet and created the Colorado Plateau. The higher land brings more rain, but the Grand Canyon area is still semi-arid. The uplift is uneven. The Kaibab Plateau, which the canyon cuts through, is over 1,000 feet (300 m) higher at the North Rim than at the South Rim. Most rainwater from the North Rim flows into the canyon, creating deeper, longer side canyons on that side. On the South Rim, shorter and steeper side canyons form.

Temperatures on the North Rim are usually lower than on the South Rim because it is higher, averaging 8,000 feet (2,400 m) above sea level. Heavy rains are common on both rims in the summer. Access to the North Rim is limited in winter because of road closures on the main route, State Route 67.

Geology

Main article: Geology of the Grand Canyon area

The Grand Canyon is part of the Colorado River basin, which has developed over the past 70 million years. For more than 150 years, scientists have studied and debated how the canyon and the river formed. Their history may involve many factors and processes that acted over time and in different places. In a 2008 study published in Science, Victor Polyak used uranium-lead dating on calcite deposits in nine caves and placed the caves' origins about 17 million years ago. Rebecca Flowers used apatite (U-Th)/He thermochronometry and suggested that parts of the canyon had reached near their modern depth around 20 million years ago. A 2012 study by Flowers suggested the western part could be as old as 70 million years. Today, many scientists think the canyon is made of several segments that formed at different times and later joined together. The "Hurricane" segment formed 50–70 million years ago, and the "Eastern Grand Canyon" was cut 15–25 million years ago. The "Marble Canyon" and "Westernmost Grand Canyon" segments were carved in the last five to six million years.

The rocks in the canyon range from the two-billion-year-old Vishnu Schist at the bottom of the Inner Gorge to the 270-million-year-old Kaibab Limestone on the Rim. Between them is a gap, the Great Unconformity, where no rock layers are found from 1.75 billion to 1.25 billion years ago. Later, layers of the Grand Canyon Supergroup formed, and many formations were laid down in warm shallow seas, beaches, and swamps. The Coconino Sandstone is a major exception, showing aeolian sand dune deposits, and parts of the Supai Group formed on land. About 65 million years ago, during the Laramide orogeny, the Colorado Plateau rose by 5,000–10,000 feet. This uplift made the stream gradient of the river steeper, helping it cut deeper (see the elevation summary of the Colorado River). Ice ages also brought more water to the river system, so it cut faster and deeper. About 5.3 million years ago, the Gulf of California opened and lowered the river's base level, which sped up erosion. This cut most of the canyon's current depth by 1.2 million years ago. The terraced walls of the canyon were shaped by differential erosion. Between 100,000 and 3 million years ago, volcanic activity covered the area with ash and lava, which sometimes blocked the river. These volcanic rocks are the youngest in the canyon.

Hydrology

Water moves through the ground in the Grand Canyon region in ways that scientists are still studying. Rain soaks into the earth and reaches the water table, forming groundwater. How easily water passes through the ground depends on the rock and soil, which is called permeability. Sand lets water pass more easily than clay. Clay layers that block water are called aquitards, and rock that holds and carries groundwater is called aquifers. The canyon's rock layers form two main aquifers. The higher C-aquifer collects water that seeps down through the rock, and the deeper R-aquifer is a karst aquifer, with many cracks in its rock where water flows.

Cracks and geologic faults and folds shape how the groundwater moves. Much of this water comes back out as springs and seeps in the canyon and its side canyons, and much of the water that could refill the aquifers is released as springs instead. Studies show that the groundwater is of different ages. Some water is only a few years old, while some is nearly 20,000 years old. Younger water often refills the upper aquifer quickly from snowmelt and rain, while the deeper R-aquifer likely depends mainly on snowmelt from the San Francisco Peaks.

History

Main article: History of the Grand Canyon area

The Ancestral Puebloans were a Native American culture centered on the present-day Four Corners area of the United States. They were the first people known to live in the Grand Canyon area, and researchers have long believed they are ancestors of the modern Pueblo peoples. Other groups also lived in the area, including the Cohonina, who were ancestors of the Hualapai and Havasupai peoples who live there today, and the Sinagua. By the time Europeans arrived in the 1500s, the Hualapai, Havasupai, and Navajo were living in the area. In 1540, Captain García López de Cárdenas traveled to the south rim of the canyon while searching for the Seven Cities of Cibola for the conquistador Francisco Vázquez de Coronado. He and his men turned back because they had run out of water, and no Europeans returned for more than two hundred years. Later explorers included Jacob Hamblin, a Mormon missionary sent by Brigham Young, who helped find places to cross the river, including the site that became Lees Ferry.

In 1869, Major John Wesley Powell led the first expedition down the Colorado River and Grand Canyon. The group set out from Green River, Wyoming on May 24 and faced dangerous rapids, lost a boat and much of its food, and often had very little to eat. Powell was the first to use the term "Grand Canyon." The canyon became a national monument in 1908 and a national park in 1919. Later, the Glen Canyon Dam, built in 1963, changed the canyon's ecosystem. Floods became much smaller, sandbars and beaches wore away, and invasive species began to replace native ones. Today, park managers face challenges that include the recent return of the California condor to the wild and the management of water and forest fires.

Weather

Weather in the Grand Canyon changes with height. The forested rims get snow in winter, but along the Colorado River in the Inner Gorge, temperatures are similar to those in Tucson and other low desert places in Arizona. The area is generally dry, but precipitation falls twice a year: in winter, Pacific storms bring rain and high-elevation snow from the west, and in late summer, the North American Monsoon brings moisture from the southeast, causing strong, local thunderstorms. The South Rim gets less than 16 inches (41 cm) of precipitation a year, including 60 inches (150 cm) of snow. The North Rim usually gets 27 inches (69 cm) of moisture, with about 144 inches (370 cm) of snow. Phantom Ranch, far below the rims at 2,500 feet (760 m), gets just 8 inches (200 mm) of rain, and snow is rare.

Temperatures change a lot during the year. Summer highs in the Inner Gorge often go above 100 °F (38 °C), and winter lows on the rims sometimes fall below zero °F (−18 °C). Visitors are often surprised, and this, along with the high altitude, can cause dehydration, sunburn, and hypothermia. Hikers should check accurate forecasts from the National Weather Service's NOAA weather radio or its official website, because the park's posted weather is only a rough guide. The National Weather Service has had a cooperative station on the South Rim since 1903. The record high there was 105 °F (41 °C) on June 26, 1974, and the record low was −20 °F (−29 °C) on January 1, 1919, February 1, 1985, and December 23, 1990. The air is usually clean, but dust storms in the Southwest, smoke from forest fires, and pollution from power plants, mines, vehicles, and cities can reduce air quality. Visibility is usually best in winter, when westerly winds bring clean air, and poorest in summer. Since 1990, the Clean Air Act has guided efforts by the US EPA to protect air quality on the Colorado Plateau. The Regional Haze Rule of 1999 set a goal of restoring visibility in the canyon to natural levels by 2064. Emissions from the Navajo Generating Station and the Mohave Generating Station were found to affect visibility, and the Mohave plant shut down in 2005. Prescribed fires in nearby forests, planned for spring and fall, help reduce the risk of severe fires.

Climate change

Temperatures have steadily risen as greenhouse gases have increased, and recent years have been the warmest in the long record. In Arizona, temperatures have gone up by 2.1 degrees Fahrenheit since 1895. Warmer weather means more water evaporates and less snow stays on the ground, so the Colorado River has less water.

The South Rim gets about 13.4 inches of rain a year, while the North Rim gets about 24 inches. Every day, 500,000 gallons of water are pumped through a pipeline from springs on the North Rim to supply the busier South Rim. As more visitors come, water use keeps growing, and both the water supply and the aging pipeline are in question. The National Park Service set goals in its "Climate Action Plan" to cut greenhouse gases 30 percent below 2008 levels by 2020 and to help the park adapt to the effects of climate change.

Biology and ecology

Grand Canyon National Park has about 1,737 species of vascular plants, 167 species of fungi, 64 species of moss, and 195 species of lichen. This variety is largely due to the 8,000 foot (2,400 m) change in elevation, from the Colorado River up to the highest point on the North Rim. The canyon has a dozen plants that are found nowhere else, and only about ten percent of its plants are exotic. Sixty-three plants here have been given special status by the U.S. Fish and Wildlife Service. The Mojave Desert affects the western canyon, the Sonoran Desert covers the eastern canyon, and ponderosa and pinyon pine forests grow on both rims. Slopes facing north get about one-third the normal sunlight, so their plants look like those at higher elevations or farther north. The canyon can connect east and west by offering habitat along its length, but it can also be a barrier for some animals, like the tassel-eared squirrel. The Park has 90 mammal species along the Colorado River, including 18 rodents and 22 bats.

The park has five of the seven life zones found in North America, from the Lower Sonoran to the Hudsonian, which is like traveling from Mexico to Canada. Elevation and climate are the main reasons for these zones. In the Lower Sonoran zone, near the river, grow Coyote willow, arrowweed, seep-willow, western honey mesquite, catclaw acacia, and tamarisk. Rare plants like the redbud, stream orchid, and Flaveria mcdougallii also live here. Endangered fish such as the humpback chub and razorback sucker swim in the river. Animals here include the canyon tree frog, red-spotted toad, Rocky Mountain toad, and bald eagle, while Leopard frogs have become very rare. Mammals include river otters, muskrats, Beavers, antelope squirrels, pocket mice, coyotes, ringtails, spotted skunks, Raccoons, weasels, bobcats, gray foxes, mountain lions, mule deer, and desert bighorn sheep. Bighorn sheep numbers have grown since 500 feral burros were removed in the early 1980s. Insects like midges, caddisflies, mayflies, stoneflies, black flies, mites, beetles, moths, and fire ants are common, along with scorpions, including the bark scorpion and giant desert hairy scorpion. Snails and slugs include mollusks, bivalves, gastropods, land snails, and slugs. Reptiles include the gila monsters, chuckwallas, and rattlesnake species.

Above the river, desert plants such as creosote bush, white bursage, brittlebush, ocotillo, mariola, four-winged saltbush, big sagebrush, blackbrush, and rubber rabbitbrush grow. Desert animals include woodrat species, the western banded gecko, and the threatened desert gopher tortoise. Higher up, insects like orange paper wasps, honey bees, tarantula hawks, stink bugs, black ants, monarch and swallowtail butterflies can be found, along with spiders such as Solifugids, wood spiders, garden spiders, black widow spiders, and tarantulas.

The Upper Sonoran zone covers most of the inner canyon and South Rim. Plants here include Utah agave, narrowleaf mesquite, ratany, and various cacti. About 30 bird species nest in the desert cliffs, and peregrines hunt there, nesting in eyrie sites on the canyon walls. Several critically endangered California condors now live in the eastern park after being re-introduced to the Colorado Plateau.

Conifer forests are home to 52 mammal species, including Porcupines, shrews, red squirrels, tassel-eared Kaibab and Abert's squirrels, black bear, and elk. The pinyon pine forests have plants like snakeweed, Mormon tea, Yucca, winterfat, Indian ricegrass, dropseed, and needlegrass, and the mountain short-horned lizard is common there. In the ponderosa pine forests on both rims, animals include rock squirrels, and plants include Utah juniper, Gambel oak, New Mexico locust, mountain mahogany, elderberry, creeping mahonia, and fescue. The Utah tiger salamander and Great Basin spadefoot toad are common amphibians there. The North Rim and Kaibab Plateau are in the Canadian zone, with spruce-fir forests of Engelmann spruce, blue spruce, Douglas fir, white fir, aspen, and mountain ash, plus wildflowers and grasses like groundsels, yarrow, cinquefoil, lupines, sedges, and asters. Mountain lions and American goshawks live here. The rare Hudsonian meadows, found only on the North Rim, have grasses like black grama, big galleta, Indian ricegrass, and three-awns, and the wettest areas have forbs.

Tourism

Grand Canyon National Park is one of the world's top natural attractions, with about five million visitors each year. In a survey of visitors from September 2003 through August 2004, 83% were from the United States, and the most common home states were California, Arizona, Texas, Florida, and New York. The South Rim is open all year when the weather allows, and the North Rim is generally open from mid-May to mid-October. Most visitors reach the South Rim from Arizona State Route 64. The South Rim has two visitor centers, a geological museum, an art gallery and bookstore, and other attractions near Grand Canyon Village. Further east is the Desert View Watchtower. The North Rim visitor center is reached by Arizona State Route 67 and is closed in winter. On the Hualapai Indian Reservation, Grand Canyon West has tourist services and the glass-bottomed Grand Canyon Skywalk, which opened in 2007 and has since attracted "thousands of visitors a year, most from Las Vegas." Also there is Guano Point, a narrow peninsula with steep drops on all sides. To the west, the Grand Canyon–Parashant National Monument has no paved roads and no visitor services.

Rafting, hiking, running, and helicopter tours are popular. The canyon floor can be reached on foot, by mule, or by boat or raft from upriver. Park officials discourage hiking down to the river and back up in one day, because of the distance, steep rocky trails, change in elevation, and the danger of heat exhaustion from much higher temperatures at the bottom. Rescues are needed each year, but hundreds of fit, experienced hikers complete the trip annually. Camping on the rims is generally limited to established campgrounds, and reservations are highly recommended, especially at the South Rim. Overnight camping below the rim requires a backcountry permit. There is at large camping along parts of the North Rim managed by Kaibab National Forest, but North Rim campsites are open only seasonally. Visitors who want a higher view can take helicopters or small planes from Grand Canyon West Airport or Grand Canyon National Park Airport, which is seven miles from the South Rim. Scenic flights are no longer allowed within 1,500 feet (460 m) of the rim inside the park, because of a crash in the late 1990s. In 2014, a developer announced plans for the Grand Canyon Escalade, a multimedia complex on the rim. On October 31, 2017, the Navajo Nation Council voted against the project.

Fatalities

About 770 deaths have occurred in the Grand Canyon between the mid-1800s and 2015. From 1869 to 2001, the most common cause was airplane and helicopter crashes, with 242 deaths. Other causes included falls, environmental causes such as heat stroke and hypothermia, flash floods, drowning in the Colorado River, and lightning strikes and rock falls. Nearly all deaths that occur are preventable.

In 1956, two commercial planes collided at 21,000 feet above the canyon. The disaster killed all 128 passengers and crew members aboard both planes. In June 2026, three hikers died from suspected heat-related illnesses in the Inner Canyon region of Grand Canyon National Park during a severe summer heatwave, when midday temperatures in shaded sections of the canyon floor regularly went above 109 °F (43 °C).

South Kaibab Trail at Cedar Ridge. O'Neill Butte on the left.