Volume of a Potential Ancient Lake in the Colorado Plateau Basin

The Bidahochi Basin, located in the southern Colorado Plateau, is a structural depression primarily bounded by the Mogollon Rim and Kaibab Uplift, filled with Miocene-Pliocene lacustrine sedimentary strata. These deposits, primarily preserved in the diatremes and maars of the Hopi Buttes volcanic field, were initially interpreted as smaller playa-like lakes (~7000 km³). Recent findings such as tufa deposits and shoreline terraces at 1800-2000 m elevation ~75 km from the Hopi Buttes suggest a much larger lake. Others have estimated this "Hopi Lake" to have a volume up to 30,000 km³. It has been hypothesized that this large lake contributed to the carving of the Grand Canyon by catastrophically overflowing the Kaibab Uplift. To better constrain the volume of the basin, a comprehensive map was created using Google Earth Pro and ArcGIS Pro. The basin outline was initially defined at the 1860 m contour, with subsequent analysis performed on merged raster data from USGS EarthExplorer. Key elevation contours (1600, 1800, 1860, 1950, 2000, and 2100 m) were selected based on prior research, and volume calculations were made using ArcGIS’s “Surface Volume” tool. Geological map units of volcanic and lacustrine deposits were also incorporated. Our analysis suggests that Hopi Lake extended further north than previously thought, reaching from the Grand Canyon's mouth to as far north as Moab, Utah, at every investigated elevation. Using the 1800 m contour, the basin reached the Uinta Mountains. Additional “basins” also appeared in Glen Canyon, Monument Valley, and west of Canyonlands National Park, with a potential outlet opening across the Cockscomb (Kaibab Uplift, Utah). Using the 1860 m contour, the shoreline runs along the Hopi Buttes, and above 2000 m, another potential outlet occurs north of the San Francisco volcanic field. At the 1860 m contour, the lake had a volume of ~40,000 km³. Breaching of much smaller ancient lakes such as Missoula and Bonneville created extensive canyon systems. Field investigations at proposed outlets or shorelines could further clarify Hopi Lake’s extent and geologic history.