Grand Canyon
What John Wesley Powell had to say about the origin of these formations -
"This high region, on the east, north, and west, is set with ranges of snow-clad mountains attaining an altitude above the sea varying from 8,000 to 14,000 feet. All winter long snow falls on its mountain-crested rim, filling the gorges, half burying the forests, and covering the crags and peaks with a mantle woven by the winds from the waves of the sea. When the summer sun comes this snow melts and tumbles down the mountain sides in millions of cascades. A million cascade brooks unite to form a thousand torrent creeks; a thousand torrent creeks unite to form half a hundred rivers beset with cataracts; half a hundred roaring rivers unite to form the Colorado, which rolls, a mad, turbid stream, into the Gulf of California.
Consider the action of one of these streams. Its source is in the mountains, where the snows fall; its course, through the arid plains. Now, if at the river's flood, storms were falling on the plains, its channel would be cut but little faster than the adjacent country would be washed, and the general level would thus be preserved; but under the conditions here mentioned, the river continually deepens its beds; so all the streams cut deeper and still deeper; until their banks are towering cliffs of solid rock. These deep narrow gorges are called canyons."
From Powell, John Wesley, 1895. Canyons of the Colorado.
Questions for thought
- Why is the snow "a mantle woven by winds from the waves of the sea"?
- As streams flow downstream, do the numbers of streams tend to become greater or fewer?
- As streams flow downstream, do streams tend to flow downhill faster or slower?
- To form these steep canyons and intervening mesas, does rain fall mainly on the plain or the high mountains beyond the plain?
- Mountain, plain and canyon - what are their relative elevations from highest to lowest?
- Powell says that if it also rained on the plain and not just the high mountains, that the "level would be preserved", what does he mean? Is he saying that rain on the plain would cause both plain and canyon to be lowered by erosion at more or less similar rates?
Web exploration
- Powell mentions high "snow-clad" mountains to the east, north, and west. Where does the Colorado River begin its downhill journey to the Gulf of California?
- How much water makes its way to the Gulf of California today? Would you call it a "mad, turbid stream"?
- How much of our water in the San Diego region comes from the Colorado River?
More information
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John Wesley Powell:
How a one-armed naturalist from Bloomington became the nation's greatest explorer
Powell, a disabled Civil War veteran, was the first leader of a scientific survey down the path of the Colorado River along the Grand Canyon. He was second Director of the U.S. Geological Survey, recognized the limited water supply in the arid western states and capped his career as founding Director of the Bureau of Ethnology at the Smithsonian Institution.
Northern Illinois University Libraries
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Colorado River
San Diego County Water Authority