Unsteady Incision Rocks the Canyonlands

Southern Utah’s famous canyon country has long puzzled and fascinated geoscientists. What accounts for the high elevation of the Colorado Plateau and for the deep exhumation of its strata? The broad plateaus edged by cliffs or cut by youthful-looking gorges, hint at a long and complex history of landscape evolution.

USU Geo’s 2024 PhD student of the year, Natalie Tanski, has tackled these questions in her dissertation research with Dr. Joel Pederson and Dr. Tammy Rittenour. A first component of Tanski’s findings were published in the journal Geology this past year, focused on the Colorado River through the unusually low-gradient Meander Canyon and then the outrageously steep Cataract Canyon, downstream of Moab, Utah.

Using a complete inventory of river terrace deposits preserved in these reaches and extensive luminescence dating, Tanski found a complex pattern of canyon incision through time. Over the past 350 thousand years, river incision has been quite rapid overall, but with distinct pauses that last 10s of thousands of years and that follow a pattern of incision as pulses or waves, moving upstream. Tanski and coauthors attribute these waves of incision to the unsteady dynamics of salt diapirism and mass wasting that mark the late Quaternary history in Cataract Canyon.

Tanski’s next publication in review is a broader study of canyon incision patterns across the central Colorado Plateau. She is finding and analyzing even larger-scale bursts and pauses of erosion that reinforce some of the great mysteries about the landscape. In the meantime, Tanski successfully defended and completed her PhD in summer of 2024!