Glen Canyon

The Glen Canyon region lies within the Colorado Plateau Province, an area of some 337,000 square kilometers drained by the Colorado River system. Glen Canyon proper is a sinuous chasm more than 480 kilometers long, variable in depth and width, through which the Colorado River once flowed. The riverbed gradient was shallow, about 1,000 meters in elevation. It is now inundated by Lake Powell.

Physiographically the canyon extends from the Dirty Devil River at the upstream end to the Paria River at the downstream end. Two other rivers, the San Juan and the Escalante, empty into Glen Canyon at about its midpoint. Some thirty smaller tributaries enter the main stem from both banks.

The walls of the Glen Canyon chasm are composed primarily of massive Jurassic-period sandstones of the Wingate, Kayenta, and Navajo type, 300-350 meters in thickness. Overlying this group in places are other Jurassic sedimentary rocks, up to 780 meters in thickness, forming the Kaiparowits, Red Rock, and Rainbow plateaus adjacent to Glen Canyon.

Two laccolithic (igneous) extrusions, the Henry Mountains (2,700-3,000 meters in elevation) and Navajo Mountain (3,050 meters in elevation), rise through the sedimentary formations. The high mountains, the deeply dissected canyons, and such erosional features as the 88-meter-high Rainbow Bridge form one of the most spectacular scenic ensembles in North America.

The region was sporadically occupied by Indian hunter-gatherers from about 6000 все. At around 300 се and again from 900 to 1300 ce, Ancestral Puebloan (formerly called "Anasazi") farmers occupied the tributary canyons and adjacent uplands.

The region was first explored by Spanish missionaries in 1776. American exploration began in the 1850s, most notably the famous river expeditions of John Wesley Powell in 1869 and 1871-72. Gold prospectors arrived in the early 1870s. There is extremely fine "flour gold" in the river gravels, but its fineness made all attempts at large-scale mining by dredges or other mechanical means unprofitable.

Tourists began boating through Glen Canyon as early as 1900. Only a few dozen trips were made until after World War II, when "river running" became increasingly popular. In the last years (about 1952 until 1963) before the Glen Canyon Dam was completed, hundreds of people made trips through Glen Canyon.

The 216-meter-high Glen Canyon Dam was constructed between 1957 and 1963. The dam has an installed hydroelectric capacity of 1,288,000 kilowatts. Lake Powell is 480 kilometers long, with over 5,076 kilometers of shoreline.

The lake has a maximum surface area of 65,320 hectares, a maximum depth of 173 meters, and a full-pool elevation of 1,100 meters. The Glen Canyon National Recreation Area, managed by the National Park Service, received over 4 million visitors in 2001. An emerging environmental problem is gasoline and hydrocarbons in the lake water from boat motors.

Environmentalists lament the loss of Glen Canyon, recalled as one of the great scenic wonders of North America, although from the time of Powell's exploration, only several hundred people ever saw it. To others, Lake Powell and its setting comprise a scenic wonder of another sort, enjoyed by millions yearly.