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I read and reread this article, hoping to find an explanation of where all those sediments have gone. From appearances, they surely all haven’t been deposited in the Gulf of California. Where else? Does anyone have any satisfying theories?

Allen Glenn
Abilene, Texas

Sediments from the erosion of the Grand Canyon have ended up in several places, says Pamela Irvine, a geologist with the California Department of Conservation’s Division of Mines and Geology in Los Angeles. Besides making up the river delta, such sediments line the valley of the lower Colorado River and also lie several thousand feet thick in California’s Imperial Valley. Moreover, Richard Young points out that a significant fraction of the rocks in the Grand Canyon are made up of limestone and other carbonate sediments that would simply have dissolved into the river and been carried to the ocean without leaving a trace .—S. Perkins