Image courtesy National Park Service

How the Grand Canyon Works

Its grandness and expansiveness have inspired jokes about what might fit within — but how big is the Grand Canyon, really? And how did it get that way? The Grand Canyon is at the heart of the 1 million acre Grand Canyon National Park in Arizona. The canyon is the largest gorge in the world and is known as one of the seven natural wonders of the world.

At the canyon's bottom flows the Colorado River. The river begins in the Rocky Mountains of Colorado and runs 1,450 miles (2,338.6 km) to the Gulf of California in Mexico. The canyon is measured by river miles — the 277 miles (445.8 km) that flow from Lees Ferry to the Grand Wash Cliffs [source: National Park Service]. Just how long is 277 miles? That's more than six times the length of Rhode Island and about the same length of Indiana [source: NETSTATE].

The width of the canyon varies. From rim to rim the average width is 10 miles (16 km), expanding to 18 miles (28.9 km) at its maximum and shrinking down to 600 feet (182.9 m) at its minimum. And from rim to river — the depth of the canyon — it averages 1 vertical mile (1.6 km) (and that's straight down, not your walking mileage if you were planning a hike!) [source: National Park Service].

How did the canyon form? And how old is it anyways? Find out in the next section.


Geology and Nature of the Grand Canyon

Geologists theorize that for millions of years, the flow of the Colorado River eroded rock in the Colorado Plateau. This slow erosion, combined with heat and uplift, created a canyon. The age of the canyon itself is a bit tricky to pin down. But the rocks that make up the canyon's stripes are extremely old — the oldest dating back nearly 2,000 million years. But because the canyon was created through the process of erosion, its age isn't the same as its oldest rocks. Erosion has simply exposed the canyon's oldest rocks. Geologists estimate the canyon itself is about 5 to 6 million years old [source: National Park Service].

Alternatively, an early Grand Canyon guide by the name of John Hance was known to jokingly claim the canyon as his own work: “It was hard work, took a long time, but I dug it myself, with a pick and a shovel. If you want to know what I done with the dirt, just look south through a clearin' in the trees at what they call the San Francisco Peaks" [source: National Park Service].

What Hance would have found had he dug the canyon, and what we're all able to see now, are the various rock strata (layers) including shale-siltstone, sandstone, conglomerate, limestone, dolomite, and igneous and metamorphic rock.

In that array of rock, several geologic periods can be seen, the oldest dating back to the Precambrian period [source:]. There are 94 types of rock (and minerals, mostly iron, that cause bright colors), as well as caves and steep-walled canyons, and a sizable fossil record (including petrified forests, lungfish, nautiloids and dinosaurs) [source: National Pak Service].

Today, the park holds a diverse set of plant and animal life. There are more than 1,500 plant species (including wildflowers and cactus) plus 355 bird species (including the endangered California condor), 89 mammalian species (including the native Bighorn sheep), 47 reptile species (including the Gila monster), nine amphibian species, and 17 fish species found in the park. More than 35 animal species are endangered or of special concern [source: National Park Service].

Next we'll walk through the history of the Grand Canyon, and study its archaeological record as well as its modern day role as a national park.

History of the Grand Canyon

The Grand Canyon is replete with archaeological remains, with more than 4,300 recorded artifacts found in a 4 percent area of the park. The earliest recorded human artifacts in the park are nearly 12,000 years old, dating to the Paleoindian period [source: National Park Service].

Since the Paleoindian period, Grand Canyon lands have been occupied. Remains have been uncovered from Archaic, Basketmaker, Ancestral Puebloan (Kayenta and Virgin branches), Cohonina, Cerbat, Pai, Zuni, Hopi and Navajo groups [source: National Park Service]. But indigenous people weren't the only ones to explore the Grand Canyon. In the early 1540s, the Spanish were reportedly the first Europeans to see the canyon when Francisco Vasquez de Coronado's expedition teams scouted the area for legendary cities of gold.

Anglos first settled in the 1880s when missionaries from the Mormon Church colonized the area. It wasn't until the summer of 1869, however, that geologist and explorer Major John Wesley Powell made the first boating expedition of the canyon's length.

After failing to be given protection in 1892, the canyon received federal protection in 1893 as a Forest Reserve. Thirty-nine years after Powell's expedition, the canyon was made a national monument. And in 1919, three years after the creation of the National Park Service, the Grand Canyon National Park was established. The Grand Canyon National Park is home to hundreds of National Historic Landmarks. In 1979, the Grand Canyon National Park was designated as a World Heritage Site.

Today, the area around Grand Canyon land is known for ranching, lumbering, hunting and, of course, tourism [source: U.S. Forest Service]. If you plan to be one of the nearly 5 million people who visit the Grand Canyon each year, get tips on viewing spots and learn about which activities you won't want to miss in the next section.

Exploring the Grand Canyon

During the park's first year in operation, it saw slightly more than 44,000 annual visitors, a number that has increased steadily. Today, nearly 5 million people visit the Grand Canyon National Park every year. By 2010, there could be up to 7.5 million annual visitors [source: National Park Service]. So what can you expect when visiting the Grand Canyon?

The weather at the Grand Canyon is unpredictable because the elevation varies from around 2,000 feet (609.6 m) to more than 8,000 feet (2,438.4 m) depending on what part of the canyon you visit and the time of year (generally, the higher the elevation the cooler the temperatures will be). During summertime, the climate is generally mild to moderate, with warm daytime temperatures, low humidity and few storms. Inner canyon temperatures, down near the river, often exceed 100 degrees Fahrenheit (37.78 degrees Celsius). However, this changes at night, when temperatures take a dramatic drop. Spring and fall bring unsteady temperatures, fog and sudden storms. Wintertime brings cold, extreme wind-chills and storms. Some roads and parts of the park close during the winter months, so be sure to double-check your route and agenda before making your plans [source: National Park Service].

Visitors to the park have a variety of activities from which to choose, including hiking, backpacking and camping, mule or horseback rides, rafting trips and scenic air tours. But the most popular activity is taking in the scenery.

There are two rims to the canyon: North Rim and South Rim. Most people see the canyon from the South Rim, which is lower in elevation than the North Rim, easier to get to and open all year. The South Rim includes some of the most popular lookout points, including Desert View, Grand Canyon Village and Hermits Rest.

Fewer people visit the North Rim, just 10 miles across the canyon from South Rim. Point Imperial, the highest accessible lookout spot, is on the North Rim, as well as other spectacular lookout spots: Cape Royal and Bright Angel Points. The 21-mile Kaibab Trail links the South and North Rims via a narrow footbridge suspended over the Colorado River and can be hiked or traversed by mule ride.

The inner canyon includes everything below the rim and can be explored by foot, mule or raft. While there are modest day trips available, exploring the inner canyon is not considered a single day expedition. Depending on the activity you choose, budget in a few days to a few weeks for your journey. A round-trip hike (or mule ride) to the bottom of the canyon is a two-day adventure. Rim-to-rim explorers should estimate three days for their one-way trip; and rafting trips generally take two or more weeks [source: National Park Service].