Grand Canyon

• 1. Introduction

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  The Grand Canyon in Arizona is 277 miles long and up to 18 miles wide. At its deepest it plunges more than a mile, a measured 6093 feet. The Colorado River cut it. Its rims are divided among a national park, a national forest, a national monument, and the lands of the Hualapai, the Havasupai and the Navajo Nation. Three questions run through what follows. How old is the canyon, a question geologists still contest? Who lived here first, and who came after? And what does it take to protect a place this large?

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• 2. Layers of Time

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  The oldest rock in the Grand Canyon sits at the bottom of the Inner Gorge. It is the Vishnu Schist, about two billion years old. On the rim lies the Kaibab Limestone, roughly 270 million years old. Between them the walls read like a book with missing pages. One gap, called the Great Unconformity, spans the time from 1.75 billion to 1.25 billion years ago, with no deposits at all. Afterward, from 1.25 billion to 730 million years ago, intermittent sediments built up the Grand Canyon Supergroup. Many of these layers formed in warm shallow seas, along beaches, and in swamps. The shoreline repeatedly advanced and retreated over the edge of a proto-North America. The Permian Coconino Sandstone is a striking exception. It holds abundant evidence of wind-blown sand dunes. Parts of the Supai Group also formed on land rather than in water. This thick, well preserved sequence is why geologists prize the canyon. It records much of the early history of the North American continent. Depth is not the reason. Nepal's Kali Gandaki Gorge is much deeper. The Grand Canyon is known instead for its overwhelming scale and its intricate, colorful landscape. Most of these layers formed below sea level, so something had to lift them high enough to be carved.

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• 3. Carving the Canyon

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  About 65 million years ago, during the Laramide orogeny, the Colorado Plateau began to rise. Over time it climbed between 5000 and 10000 feet. The lift steepened the Colorado River and its tributaries. Faster water is better at cutting through rock. The rise was uneven. The Kaibab Plateau, which the canyon bisects, stands over 1000 feet higher at the North Rim than at the South Rim. Because of that tilt, almost all runoff from the North Rim flows toward the canyon, while much of the South Rim's runoff flows away. The result is deeper, longer side canyons on the north and shorter, steeper ones on the south.

  Ice age weather added water to the river system, and the ancestral Colorado River cut faster and deeper. Then, 5.3 million years ago, the Gulf of California opened and lowered the river's base level, its lowest point. Erosion sped up. Nearly all of the present depth had been cut by 1.2 million years ago. Differential erosion shaped the terraced walls. The youngest rocks in the canyon came between 100,000 and 3 million years ago, when volcanic ash and lava spread over the area and at times completely blocked the river.

  Exactly when the cutting began is still disputed. For more than 150 years, scientists have gathered data and argued over the canyon's origins. A long-standing estimate placed the canyon's age at 5-6 million years. In 2008, Victor Polyak used uranium-lead dating on calcite deposits in nine caves, and traced their origins to about 17 million years ago. That same year, Rebecca Flowers reported results suggesting parts of the canyon reached nearly modern depth around 20 million years ago. In a 2012 study published in Science, she suggested the western part could be as old as 70 million years.

  The emerging view is that the canyon is a chain of segments that formed at different times and later joined. The Hurricane segment formed 50-70 million years ago. The Eastern Grand Canyon was cut 15-25 million years ago. Marble Canyon and the Westernmost segment, at the two ends, were carved only in the last five to six million years. Whatever the true age, Native Americans built settlements in the canyon's many caves long before anyone dated its walls.

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• 4. First Peoples

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  The word Anasazi comes from Navajo, where it means "enemy ancestors" or "alien ancestors." Modern Puebloan peoples do not prefer it. Archaeologists often used it for the Ancestral Puebloans, a culture centered on the Four Corners area and the first people known to live around the Grand Canyon. Researchers have long believed they were ancestors of today's Pueblo peoples. The Pueblo people regarded the canyon as a holy site and made pilgrimages to it.

  Other cultures lived nearby. The Cohonina lived west of the canyon between 500 and 1200, and were ancestors of the Yuman, Havasupai and Hualapai. The Sinagua occupied land to the southeast, between the Little Colorado River and the Salt River, from about 500 to 1425. They may have been ancestors of several Hopi clans.

  By the 16th century, newer cultures had taken shape. The Hualapai inhabit a 100-mile stretch of the pine-clad southern side. The Havasupai have lived near Cataract Canyon since the beginning of the 13th century, on land the size of Delaware. The Southern Paiutes live in what is now southern Utah and northern Arizona. The Navajo, or Diné, live in a broad area stretching east from the San Francisco Peaks toward the Four Corners. Archaeological and linguistic evidence suggests they descended from Athabaskan people near Great Slave Lake in Canada, who migrated after the 11th century.

  Some Third Mesa Hopi communities tell of the canyon as the place where humankind emerged from the Third World through a sipapu. The Hualapai and Havasupai reservations still border the canyon today.

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• 5. Explorers and Expeditions

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  In September 1540, Captain García López de Cárdenas reached the south rim of the Grand Canyon. Francisco Vázquez de Coronado had sent him to search for the fabled Seven Cities of Cibola. Hopi guides and a small group of Spanish soldiers went with him, arriving between Desert View and Moran Point. Pablo de Melgrossa, Juan Galeras and a third soldier climbed down about a third of the way. Lack of water forced them back. They reported that some rocks were "bigger than the great tower of Seville, Giralda." It is speculated that the Hopi guides knew routes to the floor but did not want to lead the Spanish to the river. No European visited again for more than two hundred years.

  In 1776, two priests, Francisco Atanasio Domínguez and Silvestre Vélez de Escalante, traveled along the north rim, seeking a route from Santa Fe to California. They found a crossing, once called the Crossing of the Fathers, which now lies under Lake Powell. That same year the Franciscan missionary Francisco Garces spent a week near Havasupai and called the canyon "profound."

  In 1857, Lieutenant Joseph Ives was asked to judge whether boats could travel up the river from the Gulf of California. His steamboat, the Explorer, struck a rock, and his party continued by rowboat. John Strong Newberry became probably the first geologist to visit, in 1858.

  The most famous journey began in 1869. Major John Wesley Powell had a shipwright build four reinforced rowboats in Chicago and ship them west by the newly completed Continental railroad. He hired nine men, including his brother Walter, and gathered provisions for ten months. They left Green River, Wyoming, on the 24th of May 1869. On the 7th of June they lost a boat and a third of their food, and later survived on starvation rations. They reached the Colorado River near present-day Moab, Utah, on the 17th of July.

  On the 28th of August, faced with rapids that some felt were impassable, three men left on foot toward a settlement 75 miles away. The next day, the rest of the party ran those rapids safely. Seneca Howland, Oramel Howland and William H. Dunn were killed. Who killed them has been hotly debated. The following year, Powell was told through a Mormon interpreter that the Shivwits had mistaken the men for prospectors who had murdered an Indian woman. He smoked a peace pipe with them.

  Powell used the term "Grand Canyon" in 1871. Before that it had been called the "Big Canyon." He later served as the first Director of the U.S. Bureau of Ethnology and the second Director of the US Geological Survey. In 1889, the railroad promoter Frank M. Brown led an expedition in cedar boats with no life preservers. Brown drowned near Marble Canyon. His chief engineer, Robert Brewster Stanton, built new boats and went on to the Gulf of California.

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• 6. Saving the Canyon

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  President Theodore Roosevelt visited the canyon in 1903, an avid outdoorsman and staunch conservationist. On the 28th of November 1906, he established the Grand Canyon Game Preserve. Livestock grazing was reduced, but predators such as mountain lions, eagles and wolves were eradicated. Roosevelt and his Boone and Crockett Club allies helped form the National Parks Association, which lobbied for the Antiquities Act of 1906. Once it passed, he immediately added adjacent national forest lands and redesignated the preserve a national monument on the 11th of January 1908. Land and mining claim holders blocked a national park for 11 years. President Woodrow Wilson signed the act creating Grand Canyon National Park, the 17th in the nation, on the 26th of February 1919.

  The canyon's ecosystem changed permanently with the Glen Canyon Dam in 1963. Average flood levels fell from 85,000 to 8,000 cubic feet per second. Without natural floods, sandbars and beaches eroded and invasive species began displacing native ones. Federal officials released restoration floods in 1996-2004 and 2008. In 2018 the Department of Interior began "adaptive management," using a High-Flow Experiment to shift sand and track how invasive tamarisk seeds spread. In 2022, extreme drought dropped Lake Powell's water levels and delayed a planned release.

  The air needed protecting too. The area once had some of the cleanest air in the United States. Winter visibility averages 160 miles, but summer haze cuts it to about 100. Sulfur dioxide from the Navajo Generating Station affected winter visibility. Scrubbers installed from 1997 to 1999 cut those emissions by 90 percent and lowered wintertime particulate sulfur by 33 percent. That plant shut down in 2019. The Mohave Generating Station, found to have similar effects, closed in 2005. The Regional Haze Rule of 1999 set a goal of restoring natural visibility by 2064.

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• 7. Five Life Zones

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  The elevation change of 8,000 feet, from the Colorado River to the highest point on the North Rim, gives the canyon the variety of a trip from Mexico to Canada. The park holds five of North America's seven life zones and three of its four desert types. It contains 129 vegetation communities. About 1,737 species of vascular plants grow there, along with 167 species of fungi, 64 of moss and 195 of lichen. A dozen plants are endemic, known nowhere outside the park.

  The lowest zone, the Lower Sonoran, runs from the river up to 3500 feet. Willows, arrowweed and mesquite line the banks, along with exotic tamarisk. The endangered humpback chub and razorback sucker swim in the river. Of the 90 mammal species along the river corridor, 18 are rodents and 22 are bats. Desert bighorn sheep frequent the corridor, and their numbers rebounded after about 500 feral burros were removed in the early 1980s. The canyon holds about 41 reptile species, including gila monsters, chuckwallas and six kinds of rattlesnake.

  Higher up, the Upper Sonoran zone covers most of the inner canyon and the South Rim, from 3500 to 7000 feet. Peregrine falcons find plenty of prey and nesting ledges here. Several critically endangered California condors have made the eastern part of the park home. Ponderosa pine forests grow between 6500 and 8200 feet on both rims. The canyon can even act as a genetic barrier. It divides populations of the tassel-eared squirrel.

  Spruce-fir forests of the Canadian zone cover the North Rim and Kaibab Plateau from 8,200 to 9,000 feet. Mountain lions, Kaibab squirrels and American goshawks live there. The final zone, the Hudsonian, holds rare montane meadows and subalpine grasslands found only on the North Rim.

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• 8. Visitors and Dangers

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  About five million people visit Grand Canyon National Park each year. A survey from September 2003 through August 2004 found that 83 percent were from the United States, with California the top state at 12 percent. About 90 percent of tourists go to the South Rim. The North Rim is generally open from mid-May to mid-October. A third major area, Grand Canyon West on the Hualapai reservation, opened the glass-bottomed Skywalk in 2007.

  In 2014, a developer announced the Grand Canyon Escalade. It would put shops, an IMAX theater, hotels and an RV park on 420 acres of rim, with a gondola down to the canyon floor. On the 31st of October 2017, the Navajo Nation Council voted against it.

  Overnight trips below the rim need a backcountry permit. The park receives about 30,000 requests yearly and issues 13,000 permits, yet close to 40,000 people camp overnight. Park officials discourage hiking from rim to river and back in a single day. Summer highs in the Inner Gorge commonly exceed 100 F, while rim temperatures sometimes fall below 0 F. Rescues of unsuccessful rim-to-river-to-rim hikers occur every year.

  About 770 deaths occurred between the mid-1800s and 2015. Of those from 1869 to 2001, aircraft crashes caused the most, with 242 deaths. In 1956, two commercial planes from Los Angeles collided at 21,000 feet above the canyon, killing all 128 people aboard. At the time it was the deadliest commercial aviation disaster in history. Scenic flights are now barred from flying within 1500 feet of the rim in the park, because of a late 1990s crash. Drowning in the Colorado River claimed 79, and falls claimed 53.

  Visitors also strain the water supply. Every day, 500,000 gallons are pumped from springs on the North Rim through the Transcanyon Pipeline to serve the more heavily developed South Rim. As of 2019, plans were proposed to replace the aging 16-mile aluminum pipeline.

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