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Grand Canyon Geology via the Colorado River
(Image from the National Park Service website)
August 13, 1869
"We are now ready to start on our way down the Great Unknown... We are three quarters of a mile in the depths of the earth, and the great river shrinks into insignificance as it dashes its angry waves against the walls and cliffs that rise to the world above; the waves are but puny ripples, and we but pygmies, running up and down the sands or lost among the boulders...We have an unknown distance yet to run, and an unknown river to explore. What falls there are, we know not; what rocks beset the channel, we know not; what walls rise over the river, we know not. Ah, well! We may conjecture many things. The men talk as cheerfully as ever; jests are bandied about freely this morning; but to me the cheer is somber and the jests are ghastly."
--John Wesley Powell
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| This happy crew of AWG rafters are shown in Saddle Canyon, enjoying a cool waterfall after hiking up from the Colorado River. [larger image] | View looking downstream from the trail to an ancient storage cache, probably used to store maize and other seasonal items. The cache is high above the river level, at the base of the steep cliff formed by the Redwall Limestone. The maize was grown on a delta built out into the river at the mouth of a side canyon. Note the reddish color of the river, caused by sediment brought in from the canyon of the Little Colorado River. [larger image] |
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| Put your finger on a billion years of Earth history! The Great Unconformity is a surface that represents an immense amount of geologic time. The near-vertical foliation of the Precambrian metamorphic rocks is truncated by the erosional surface, which is overlain by conglomerate and sandstone of Cambrian age, shown here in Blacktail Canyon. [larger image] | These hikers are shown perched among cliffs of Cambrian Tapeats sandstone. The sandstone shows evidence of tidal influences on deposition. This hike also traverses the Grand Canyon Series rocks, a Precambrian sedimentary sequence preserved in a graben. [larger image] |
