Day 6: "colorado" & Upper Granite Gorge section

above: After the rains of the previous days and also joining with the Little Colorado River the river became increasingly sediment laden. The root of the Spanish word "colorado" means colored, but it is usually used in the sense of a reddish color, especially a rusty red color. The river was certainly living up to its name.

At this point the water is the consistency of cream rather than water and it seems slick and almost oily. John Wesley Powell was said to have muttered that it was "too thick to drink and too thin to plow". To someone from New England, where a suspended solids measurement of 10-20 mg/l indicates dirty water, the Colorado River, where the measurement can be up to 750,000 mg/l, is a rude shock. That means that 3/4 of the weight of a cup of water is in the suspended solids.

  dikes in basalt
upper granite gorge  

The Granite Gorges, where the river has exposed the oldest (1.84 to 1.68 BYA - billion years ago) rocks, is also where it is the deepest - about a mile from the river up to the rim. The dark basalts you see are part of the earth's underlying crust, igneous rock that was once molten. They are shot through with "dikes" of lighter granitic rocks that squeezed their way in from below after the darker basalts had hardened and then cracked from movements in the earth's crust.

These older rocks are exposed in three areas in the canyon: here in the Upper Granite Gorge, and also in the Middle Granite Gorge and Lower Granite Gorge.

Next Page
Return to Index