27 A POTENTIAL LAKE IN THE COLORADO PLATEAU Andrew R. Floyd | andrewfloyd@cedarville.edu | School of Science and Mathematics | Cedarville University | 251 N Main St, Cedarville, OH 45314 USA April 2025 ICC New Scholars Conference | Cedarville University 2025 Annual Scholars Symposium ABSTRACT: The southernmost area of the Colorado Plateau, known as the “Bidahochi Basin,” is a structural depression over much of the Little Colorado River. The basin is primarily bounded by the Mogollon Rim and the Kaibab Uplift and is filled with Miocene-Pliocene sedimentary strata that reflect a lacustrine environment, most notably preserved in the diatremes and maars of the Hopi Buttes. Initially interpreted as remnants of smaller playa-like lakes (~7000 km³), recent discoveries of tufa deposits and shoreline terraces at 1800-2000 m elevations suggest a larger lake. Others have estimated this “Hopi Lake” to have volumes up to 30,000 km³ (Dallegge et al. 2003). Due to its size and proximity to the Grand Canyon, others have hypothesized that this large lake contributed to the carving of the Grand Canyon by catastrophically overflowing the Kaibab Uplift (Austin et al. 2023; Douglass and Gootee 2024). Alternative theories have also been suggested, such as karst piracy (Hill and Polyak 2014) or serial lake spillover models. Given these interpretations, creating a comprehensive map to better analyze the basin is essential. The basin was initially outlined in Google Earth Pro using the polygon tool at the 1830 m contour, providing a rough surface area estimate. All subsequent analyses were performed in ArcGIS Pro. Raster data for the Colorado Plateau was acquired from USGS EarthExplorer and merged into a mosaic. A fitted polygon, created in Google Earth Pro and imported into ArcGIS, was used to trim the raster. This trimmed raster generated 20m elevation contours for the basin. Six key elevations—1600, 1800, 1860, 1950, 2000, and 2100 meters—were selected based on prior research and converted into polygons. Volume calculations for each elevation were made using ArcGIS’s “Surface Volume (3D)” tool. Notable features and Mogollon Rim/Kaibab Uplift gaps were recorded, and relevant geologic map units were included to highlight the basin’s volcanic and lake deposits. Hopi Lake extended much further north than previously thought, reaching from the Grand Canyon’s mouth up to Moab, Utah, at each studied elevation. At elevations above the 1800 m contour, it reached the Uinta Mountains. Additional “basins” appeared in Glen Canyon, Monument Valley, and areas west of Canyonlands National Park. A lake “outlet” also opened north of the Vermillion Cliffs across the Cockscomb (Kaibab Uplift, Utah). At the 1860 m contour, a “shoreline” lies along the Hopi Buttes, and above the 2000 m contour, another outlet occurs north of the San Francisco volcanic field. Volumes for each elevation are shown in Table 1. Our analysis suggests Hopi Lake extended farther north, possibly suggesting a serial lake spillover model. With a volume of ~40,000 km³, it could have catastrophically carved the Grand Canyon, similar to how Lake Missoula (~2600 km3) or Lake Bonneville (~10,000 km³) shaped their respective drainages (Smith 2006; O’Connor et al. 2020). Based on its current elevation, the Hopi Buttes volcanic event may also have contributed to Hopi Lake’s overspill, possibly uplifting and displacing enough water to overtop the Kaibab Uplift. Field investigations at proposed outlets or shorelines could further clarify the lake’s true extent and geologic history. METHODS AND RESOURCES: GOOGLE EARTH PRO: - Downloaded and used EarthTopoMap overlay and outlined smaller basin by hand with the Path tool - Used EarthTopoMap overlay to then manually outline the Bidahochi Basin following a proposed elevation (1830m) using the polygon tool. - Provided a surface area estimate, but not volume. Additionally, it did not fully capture the entire basin’s extent upstream the Colorado River. ARCGIS PRO: - Downloaded quadrangle DEM .tif files from USGS EarthExplorer website and uploaded them to ArcGIS Pro - The rasters were combined into a raster mosaic (“Raster to Mosaic”) - Mosaic was then clipped by an imported polygon created in Google Earth with the polygon tool (“KML to Feature” ; “Clip Raster”) - 20m contours were extracted from the mosaic (“Contour”) - Desired contours were then isolated and made into separate layers (“Select by Attribute” ; “Make Layer From Selected Features”) - Volumes for each desired elevation contour were then calculated using the “Surface Volume Tool” - Lake polygons were created by closing off gaps where appropriate and converting the line feature to polygon - Additional geological data (Bidahochi Fm polygons and Volcanics) were imported from USGS and Arizona geologic shapefiles. DISCUSSION: The elevations investigated in this project suggest that ancestral Hopi Lake held at least 10,000 km³ of water, comparable in scale to Lake Bonneville. Considering the significant erosional capabilities demonstrated by both Lake Bonneville and Lake Missoula, Hopi Lake having the same or larger scale destructive potential is plausible. Volumes at higher elevations suggest a range of 30,000 to 70,000 km³ of water, and if such a lake were to overflow the Kaibab Uplift, it could easily have eroded the Grand Canyon. The maps at each elevation also revealed a potential “outlet” or “gap” located north of the mouth of the Grand Canyon at the Cockscomb (Utah). At the elevations 1960m, 2000m, and 2100m, another “outlet” appears south of the Grand Canyon near Flagstaff, AZ. The elevation of current Bidahochi Fm outcrops would be completely underwater at these higher lake level elevations. If 1860 is correct, that suggests that uplift of the Bidahochi Fm occurred in the area of the Hopi Buttes volcanic field. These maps may also serve as a guide for further “shoreline” investigations. Although much has likely changed topographically in the Colorado Plateau since the lake last existed, there may be remnants of shoreline or tufa deposition further north to north-west of the Grand Canyon’s mouth in addition to what has already been found. LAKE VOLUME RESULTS REFERENCES: Austin S.A., E.W. Holroyd III, T.F. Folks, and N. Loper. 2023. Shoreline transgressive terraces: Tufa-encrusted landforms indicate rapid filling and failure of Hopi Lake, western Bidahochi Basin, northeastern Arizona. In J.H. Whitmore (editor), Proceedings of the Ninth International Conference on Creationism, pp. 346-362. Cedarville, Ohio: Cedarville University International Conference on Creationism Dallagge T.A., M.H. Ort, W.C. McIntosh. 2003. Mio-Pliocene Chronostratigraphy, Basin Morphology and Paleodrainage Relations Derived From The Bidahochi Formation, Hopi and Navajo Nations, Northeastern Arizona: The Mountain Geologist 40, no. 5:55-82. Douglass J., and B.F. Gootee. 2024. Discovery of beach sand, beachrock, and capping tufa on Balakai Mesa: Implications for the Bidahochi Formation and the overflow origin of the Grand Canyon: Open-File Report 24-02, 9 p. University of Arizona: Arizona Geological Survey. Hill C. A., and V. J. Polyak. 2014. Karst Piracy: A Mechanism for Integrating the Colorado River across the Kaibab Uplift, Grand Canyon, Arizona, USA. Geosphere 10, no. 4:627–40. DOI: 10.1130/GES00940.1 O’Connor J.E., V.R. Baker, R.B. Waitt, L.N. Smith, C.M. Cannon, D.L. George, R.P. Denlinger. 2020. The Missoula and Bonneville floods—A review of ice-age megafloods in the Columbia River basin: Earth-Science Reviews 208, pp. 1-51. DOI: 10.1016/j.earscirev.2020.103181 Smith L.N. 2006. Stratigraphic evidence for multiple drainings of glacial Lake Missoula along the Clark Fork River, Montana, USA. Quaternary Research, no. 66:311-322. DOI: 10.1016/j.yqres.2006.05.009 ACKNOWLEDGEMENTS: I would like to thank Dr. John Whitmore and Dr. Sean O’Donnell for their guidance and advice, and Dr. Mark Gathany for assistance with the ArcGIS Pro software. I would also like to thank my fellow senior classmates for their tips and critques along the way. I would also like to thank all the other geology students who provided suggestions and endured my excitment and frustrations in the lab. Legend Volcanics Proposed Hopi Lake (1860 m elev) Bidahochi Fm. 4283 767 Elevation Raster (m) Tufa and Shoreline Exposures Shoreline Terraces Tufa 2025 New Scholars Floyd, A. 2025. Volume of a potential lake in the Colorado Plateau Basin In J.H. Whitmore (editor), Proceedings of the 2025 New Scholars International Conference on Creationism, pp. 26-27. Cedarville, Ohio: Cedarville University International Conference on Creationism [poster presentation]. New Scholars 2025
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