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The Grand Canyon

USA

View from the South Rim near Yavapai Point looking across the inner gorge (in shadow) to the North Rim. Sunset lighting accentuates the horizontal Paleozoic strata. (Photo Credit: Michael Quinn, NPS).

Geological Period

Pliocene and Pleistocene

Main geological interest

Geomorphology and active geological processes

Location

Colorado Plateau region of the USA.
36°03’56.0″N, 112°07’04.0″W

View from the South Rim near Yavapai Point looking across the inner gorge (in shadow) to the North Rim. Sunset lighting accentuates the horizontal Paleozoic strata. (Photo Credit: Michael Quinn, NPS).

Earth’s iconic canyon provides an archive of two billion years of earth’s history and a globally important laboratory for research and education.

Grand Canyon is one of the most visited of the USA’s National Parks. Its geologic record spans seven geologic eras and much of Earth’s biologic evolution history with well exposed sedimentary rocks containing rich fossil assemblages. Its stunning landscape includes a 1.6-kilometer-deep gorge that ranges in width from 500 m to 30 km and twists and turns for a length of 445 km. The canyon formed in the past 6 million years by the erosional power of the Colorado River and its tributaries, deepening older paleocanyon segments (Karlstrom et al., 2014) and carving through an uplifting Colorado Plateau. Geoscience education efforts (Karlstrom and Crossey, 2019) also have global reverberations in terms of understanding how human and geologic timescales interact.

Vishnu basement rocks deep in the inner gorge record the assembly of this part of the North American continent. (Photo Credit Ron Chappell).

  • Geological description

Grand Canyon is 1.6-km-deep and is being carved into the uplifting Colorado Plateau by the erosional power of the Colorado River and its tributaries (Karlstrom et al., 2022). It exposes an exceptionally complete rock record of 1.84 billion years (about 40%) of Earth’s history. A visit to the rims, a hike into the canyon, or a river trip through its 445-km length are awe-inspiring experiences. They motivate >6 million annual visitors to ponder the depths of geologic time and how humans are part of Earth’s history and processes. Vishnu basement rocks, exhumed from 25 km depths, formed via collisions of volcanic island chains between 1,840 and 1,375 million years ago. Grand Canyon Supergroup records basins within the continent that responded to assembly and breakup of an early supercontinent of Rodinia between 1,250 and 729 million years ago, a time dominated by single-celled life. The flat-lying layered Paleozoic rocks encode stories, layer by layer, of dramatic environmental changes and the evolution of animal life between 530 and 270 million years ago. The iconic landscapes of the region are dynamic and provide a key laboratory for understanding interactions among geomorphic, volcanic, tectonic, and anthropogenic processes.

  • Scientific research and tradition

Building on scientific research extending back to the 1850s (Karlstrom and Crossey, 2019), there is ongoing research on most rock units and many aspects of geomorphology. Hot topics include middle crustal processes, evolving Precambrian Earth systems, the Cambrian explosion (Karlstrom et al., 2020), age and integration of the Colorado River (Crow et al., 2021), rates and processes of canyon carving, and arid land hydrogeology.

Stratigraphic column of the three sets of rocks and major unconformities (from Karlstrom et al., 2021).

  • Reference

Crow, R.S. et al. (2021) ‘Redefining the age of the lower Colorado River, southwestern United States’, Geology, 49(6), pp. 635–640. Available at: https://doi.org/10.1130/G48080.1.

Karlstrom, K. et al. (2021) Telling Time at Grand Canyon National Park 2020 Update Telling Time at Grand Canyon National Park 2020 Update. (Natural Resource Report NPS/GRCA/NRR, 2021/2246). Available at: https://doi.org/10.36967/nrr-2285173.

Karlstrom, K. and Crossey, L. (2019) ‘Classic Rock Tours 3. Grand Canyon Geology, One Hundred and Fifty Years after John Wesley Powell: A Geology Guide for Visiting the South Rim of Grand Canyon National Park’, Geoscience Canada, pp. 163–193. Available at:https://doi.org/10.12789/geocanj.2019.46.153.

Karlstrom, K.E. et al. (2014) ‘Formation of the Grand Canyon 5 to 6 million years ago through integration of older palaeocanyons’, Nature Geoscience, 7(3), pp. 239–244. Available at: https://doi.org/10.1038/ngeo2065.

Karlstrom, K.E. et al. (2020) ‘Redefining the Tonto Group of Grand Canyon and recalibrating the Cambrian time scale’, Geology, 48(5), pp. 425–430. Available at: https://doi.org/10.1130/G46755.1.

Karlstrom, K.E. et al. (2022) ‘Tectonics of the Colorado Plateau and Its Margins’, Annual Review of Earth and Planetary Sciences, 50(1), pp. 295–322. Available at: https://doi.org/10.1146/annurev-earth-032320-111432.

  • Author(s)

Karl E. Karlstrom
Distinguished Professor, Department of Earth and Planetary Sciences, University of New Mexico, USA

Laura J. Crossey

Distinguished Professor, Department of Earth and Planetary Sciences, University of New Mexico, USA

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