Theories on the Age of the Grand Canyon

Wilson Salls

Abstract: The Grand Canyon is possibly the most iconic of the U.S.’s natural treasures, yet the nature of its origin remains a mystery. Fervent controversy plagues discussions of its age. Dozens if not hundreds of studies have been conducted since the late 19th Century on formation of the canyon and the intrinsically tied paleohydrology of the southwest, particularly the Colorado Plateau. Uplift of the Colorado Plateau by the Laramide Orogeny has unquestionably been one of the largest factors impacting Grand Canyon formation, creating the base level change necessary for such a canyon to be carved. Yet, various studies provide evidence for seemingly conflicting ages and explanations of carving.

Most fundamentally, debate originated around whether river carving can be described by antecedence, in which the river pre-dates landscape warping, or superposition, in which the newly warped landscape determines the path of the river. Later studies indicated that the Colorado River as we know it today is unlikely to have been responsible for most of the Grand Canyon’s incision—rather, two or more separate drainages became connected in order to form today’s hydrologic system. Currently, debate still hinges on whether the canyon is “young” or “ancient.” Dating of basalts within the canyon seem to provide solid evidence that a majority of incision occurred since 5 Ma or less, yet speleothem dating and apatite grain cooling histories suggest an age as old as 70 Ma. This study summarizes relevant literature since 1875, providing a sense of the enormous variety of theories throughout that time.