What to see in America . and mighty floods. Greatquantities of earth and rock and uprooted trees rush likean avalanche into the main stream from the side driftwood over one hundred feet above the ordinarywater level indicates the magnitude of the wild floods. Theprocess of excavation is still in active operation. It willcontinue until the river reaches so low a grade that it canno longer move the debris. Then the side streams will cutaway the adjoining walls, and the canyon will widen untilits sides become gentle slopes. But this is likely to require amillion years or more. The
What to see in America . and mighty floods. Greatquantities of earth and rock and uprooted trees rush likean avalanche into the main stream from the side driftwood over one hundred feet above the ordinarywater level indicates the magnitude of the wild floods. Theprocess of excavation is still in active operation. It willcontinue until the river reaches so low a grade that it canno longer move the debris. Then the side streams will cutaway the adjoining walls, and the canyon will widen untilits sides become gentle slopes. But this is likely to require amillion years or more. The gorge is filled with mountains,some of them five thousand feet high. Perhaps nowhere elseis the crust of the earths surface so exposed to view. Duringone period of volcanic activity a number of lava streamsburst into the canyon through the walls, and others flowedover the brink. They filled it to a depth of about fivehundred feet for a distance of sixty miles, but much of thislava has since been eroded away. Arizona 451. The Grand Canyon and Colorado River
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Keywords: ., bookauthorjohnsonc, bookcentury1900, bookdecade1910, bookyear1919
