• SOUTH RIM OPEN ALL YEAR
NORTH RIM OPEN MAY 30 TO SEPTEMBER 30, INCLUSIVE •
GRAND CANYON NATIONAL PARK is situated in the northern portion of Arizona, which is one of the most colorful and picturesque sections of the United States. The Grand Canyon has been cut in a forested plateau surrounded by a semiarid region of bare cliffs and desert plains. The height of the plateau, through which the Colorado River has cut the canyon, gives to this section a splendid, cool climate during the summer months. The flat country back from the rim and partially within the park, is covered with a verdant stand of coniferous trees; the North Rim, in fact, includes a part of one of America's most beautiful forests, the Kaibab. Park elevations range from 1,850 feet along the Colorado River in the bottom of the canyon to 9,100 feet on the North Rim.
A large part of geologic history is revealed more clearly in the walls of Grand Canyon than in any other place in the world. Forming the walls of a narrow inner gorge in the lower part of this canyon are some of the oldest rocks (Archean) known to geologists. These were largely sediments (limestones, shales, and sandstones) originally, but have been so altered by the great heat and pressure of mountain-making movements that their original character is entirely lost. No traces of life have survived the great metamorphism of the rocks of this first era.
Here and there in the lower parts of Grand Canyon may be seen groups tilted rock layers of the second era (Algonkian), remnants of a second series of mountains that existed in this region. These rocks are the oldest to retain their original character, for in them may be recognized pebbles, sand grains, mud and lime. Furthermore, in these rocks are found the oldest definite traces of life.
The horizontal strata (Paleozoic) which form the upper canyon walls and which lie on the erosion-truncated edges of the older rocks in the canyon bottom, were partly formed as deposits of sand, mud, and limy ooze in the waters of ancient seas, as shown by the presence of entombed shells and other remains of marine organisms. Others of these rocks, however, were deposited as sediments on land, as shown by fossils of land plants and animals and by sloping beds in sandstone, such as may be seen in sand dunes today.
The detail and simplicity of the history of the earth as told in the rock layers of Grand Canyon are unsurpassed. Remnants of ancient mountains, of sea bottoms, river beds, and deserts millions of years old are herein represented. Even a casual investigation will show many and varied fossil plants and animals.
The Grand Canyon has been formed by the work of running water as the region has been slowly elevated. As the formations in the upper canyon walls lie in orderly horizontal layers, like beds of masonry, they have been carved into definite architectural forms which are everywhere comparable in profile though varied and irregular in plan. As they vary in their resistance to erosion, some being hard and some soft, every part of the canyon walls, every pinnacle and butte, is characterized by its own steplike alternation of cliff, slope, and shelf. Each resistant bed stands forth as a cliff, and each weak bed is marked by a slope. Each shelf or platform is made by the wasting back of a weak stratum that lies upon a resistant, cliff-making stratum, and the greater the thickness of the weak stratum, the broader the shelf. The plateaus that border the canyon are themselves simply great terraces developed on a resistant formation, a thick limestone, from which overlying softer beds have been eroded away.
As erosion goes on, parts of the canyon wall or plateau become separated by the cutting of branch canyons and stand as solitary pinnacles capped by remnants of a hard bed of rock. These remnants are the buttes and temples. The great height of the plateau gives rapid fall to the streams that are tributary to the Colorado River, enabling them to cut deeply and to carve rock forms that are fashioned on a gigantic scale. The erosion accomplished by these streams, though spasmodic because the streams are mainly fed by intermittent rainstorms in an arid climate, is none the less effective. The desert plants grow sparsely so the slopes are partly bare of vegetation. The concentrated energy of a single torrential shower, therefore, may wreak more havoc than would be caused by a season's rainfall on a plant-covered slope in a humid region. It is this prevailing aridity that, by retarding the growth of vegetation and the formation of soil, keeps sharp and fresh profiles that in a moist region would soon be dulled or obscured.
Although the Grand Canyon is 217 miles long, measured by course of the Colorado River, only about one-half of it, the first 105 miles west of Marble Canyon, is included within the boundaries of Grand Canyon National Park. The Canyon is from 4 to 18 miles in width and has an average depth of approximately 1 mile.
The Colorado is the second longest river in the United States and cuts 19 major canyons along its course. Where measured at the gaging station in Grand Canyon, it is 300 feet wide and flows from 2-1/2 to 20 miles per hour in speed. Estimates indicate that it varies from 12 to 42 feet in depth and carries past the gaging station an average of nearly 1,000,000 tons of sand and silt every 24 hours. This river has two main sources, one in southwestern Wyoming, the other in northern Colorado. Many large tributaries add to its volume as it flows some 2,000 miles to its delta at the upper end of the Gulf of California.
Boulder Dam is 260 miles downstream from the Kaibab Suspension Bridge near the bottom of Grand Canyon. The water backed up by the dam will come to within about 60 miles of the park boundary on the west so that it will have no effect on the Colorado River so far as the Grand Canyon National Park is concerned.
The wide range of plant and animal life found within the park boundaries includes about 180 species of birds, 60 species of mammals, 25 reptiles, and 5 amphibians. Wildflowers bloom during the summer season, and there are many varieties of trees and shrubs. Among the larger mammals are the Rocky Mountain mule deer, mountain sheep, antelope, cougar, coyote, and bobcat. The smaller mammals include two beautiful species of squirrels, the Abert on the South Rim and the white-tailed Kaibab which is found nowhere else in the world except on the North Rim.
In Grand Canyon four distinct climatic and plant zones have been produced by the extreme variations in altitude from the Canyon bottom to the North Rim. In the lower part of the Canyon Mexican desert conditions prevail while on the high parts of the North Rim Canadian types are found. The South Rim, with an elevation which averages about 7,000 feet above sea level, is in a transition or intermediate zone.
Traces of ancient Indian life are abundant in the region. Some 300 ruins of ancient pueblo dwellings have been found on the rims, and along the cliffs within the Canyon are numerous cliff dwellings dating back seven or eight centuries.
The Indians of the Grand Canyon region today represent four distinct nations. The pastoral Navajos and the pueblo-dwelling Hopis live just to the east in their respective reservations, the agricultural Havasupais to the west live in Havasu Canyon within the boundaries of Grand Canyon National Park, and the Paiutes on the plains to the north.
Grand Canyon National Park is under the jurisdiction of the Director, National Park Service, Department of the Interior, Washington, D. C. The headquarters development is located on the South Rim. The address of the park superintendent, Miner R. Tillotson, is Grand Canyon, Ariz. The office of the superintendent is at the terminus of the south approach road, southwest of the depot.
Mail to the South Rim should be addressed to Grand Canyon, Ariz., and to the North Rim, to Kaibab Forest, Ariz.
A free information bureau is maintained on the South Rim by the National Park Service in the Administration Building. Park visitors are welcome and are advised to apply to the ranger in charge of this bureau for official information of any kind and for lost and found articles. A small reference library is available for the use of visitors, and Government maps and other publications relating to the Grand Canyon may be consulted or secured here.
Motorists are requested to register at this office, unless previously registered at one of the checking stations.
During the summer, members of the naturalist staff conduct automobile caravans and other trips along the Canyon rim, explaining features relating to the natural history of the Canyon. Full information regarding these trips may be had at the Park Information Office.
Similar information service is available to the North Rim visitor at the north entrance checking station, at the Bright Angel Point ranger station, and through the rangers on duty at various points. Nature walks and automobile caravan trips on the North Rim are made regularly during the season under the guidance of ranger naturalists.
The National Park Service welcomes all comments which will improve service. These should be made in writing and addressed to the Superintendent, Grand Canyon National Park, Grand Canyon, Ariz.
For the purpose of clarity details regarding facilities are given separately for the South Rim and the North Rim. Information on the South Rim follows immediately, and that on the North Rim is given on pages 23 to 31.
Last Updated: 20-Jun-2010