A recent survey of 362 archaeological sites along the Colorado River through Grand Canyon shows most of them are eroding due to the influence of Glen Canyon Dam…Stone dwellings, roasting pits and other culturally significant sites in the Grand Canyon are protected by windblown river sand. But when Glen Canyon Dam was built six decades ago, it trapped the sediment, leaving the sites exposed to erosion. Joel Sankey of the U.S. Geological Survey is the study’s lead author.