A short history of ideas on the origin of the Grand Canyon

Abstract

—For as well known and highly regarded as the Grand Canyon is, its precise age and the specific processes involved in its formation remain somewhat elusive to the geologist. This is not due to a lack of trying, for the great gorge has been the subject of passionate inquiry since John Strong Newberry first laid eyes on it over 155 years ago. Research into the canyon’s origin has accelerated greatly since the turn of the millennium and a survey of the ever evolving ideas related to its development can serve to frame the foundations of many modern proposals. Historic ideas on the canyon’s origin gener- ally sought to relate the deeply dissected modern landscape (that continues to captivate practically anyone who encounters it), with the possible evolution of the Colorado River. The earliest geologists however, could not perceive of the dynamism that can be involved in a rivers’ history, nor could they benefit from a larger understanding of the tectonic evolution of the American Cordillera. It took nearly seventy years of research before definitive evidence was found that showed that the modern Colorado River, one that begins in the Rocky Mountains and drains across the elevated Colorado Plateau to the foundered Basin and Range and the Gulf of California, might actually be one of the younger geologic features found upon the southwestern landscape. Since this relative youthfulness of the river has been detected, myriad searches for prior ancestors, cut-off chan-nels, past configurations, or flow reversals have been postulated, presented, debated upon and accepted or rejected. Ideas that the river and canyon might be as old as the Laramide Orogeny have never gone away but consensus points to younger dates. A familiarity with historic theories for how the Grand Canyon and Colorado River evolved is presented below to help to frame modern debate.