New paper: Quaternary deformation on the southern flank of the Yellowstone Hotspot

New Paper

New Paper led by Daphnee Tuzlak. With Joel Pederson and Tammy Rittenour

Underneath Yellowstone National Park sits one of the largest active super volcanoes on Earth. It has intrigued scientists and non-scientists for decades. A hot zone in Earth’s mantle below Yellowstone is generating magma, supports high topography, and makes the region one of the fastest deforming on the North American continent. Over more than 15 million years, the North American Plate has been slowly drifting southwest over the hot mantle and has left a track of volcanic centers that spans from Nevada to Montana. The hot mantle lifts the crust above it, but the abandoned volcanic centers in the wake of the hotspot track sink back down. Thus, uplift and subsidence from the hot spot interact with the mountain topography that formed millions of years before its arrival. If this complex setting isn’t enough on its own, repeated glaciations and rivers carved into the uplifting crust and formed an intricate topography.

Overview of the Study Area. Volcanic centers are marked in light red. White-shaded area mark the extent of Ice during the Last Glacial Maximum (~13,000 – 20,000 years ago). White dotted line is the outline of Yellowstone National Park. Fine and solid white lines are state borders.

We set out to study how uplift above the hotspot, subsidence in its wake, major crustal faults, and changes in climate shaped the landscape over the late Quaternary (the past 100 thousand years). To this end, we explored trunk drainages of the Snake River system that flow from high up on the uplifting center of the Yellowstone region into the subsiding Snake River Plain west of Yellowstone. By analyzing the patterns of steepness and energy along the Snake River and its tributaries and by estimating the age of abandoned terraces that mark the river’s history, we found that the Snake River has been episodically cutting into the uplifting mountains at an average rate of ~0.3 mm/y. We also found that the pattern of incision is not dominated by broad uplift of the crust above the Yellowstone hotspot but rather by the movement of individual faults and the subsidence of the Snake River Plain downstream. Thus, we shed light on the dominant tectonic processes that have shaped the landscape over the past 100,000 years.

Fluvial gravels overlying tilted bedrock on a terrace along the Hoback River; tributary to the Snake River

This work was led by Daphnee Tuzlak and Joel Pederson at Utah State University. Sand samples from river terraces were dated together with and Tammy Rittenour at at the Utah State University Luminescence Lab. My work within this project was supported by an EarthScope AGeS Program geochronology student award funded by the National Science Foundation.

Fault scarp of the Hoback fault (~3.5 m-high) on a ~14,000 year-old fluvial terrace indicating average slip of ~0.25 mm/year

Tuzlak, K., Pederson, J.L., Bufe, A., Rittenour, T.M. (2021). Patterns of Incision and Deformation on the Flank of the Yellowstone Hotspot — Alpine Canyon of the Snake River, WY. Geological Society of America Bulletin. Journal Link.