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Bryce Canyon National Park has the greatest concentration of hoodoos on Earth, and the standard explanation for how they formed comes from one unpublished dissertation. So writes Claire Crise, a seasonal ranger, in the “Perspectives” section of Park Science (Volume 36, Number 1, Summer 2022). If the explanation is right, a warming climate could be literally reshaping the park, but how is unknown.
The rock and the idea
Roughly fifty million years ago the area was a shallow, swampy freshwater lake more than 200 miles long. Over 25 million years, sediments washed in from the surrounding mountain streams and built up in layers that formed the fragile Claron limestone of the hoodoos, which rise in columns, towers and bridges.
Bryce Canyon holds the highest concentration of hoodoos on Earth. Photo: NPS / Claire Crise.
The park ranges from 6,600 to 9,100 feet in elevation, so temperatures swing sharply, and about 170 days a year pass through freezing and thawing in a single day. The freeze-thaw cycle, physical weathering by ice that breaks rock apart, is believed to be the leading cause of hoodoo creation, and may give the formations their angular shapes and names like Thor’s Hammer, Queen Victoria and The Alligator.
Thor’s Hammer. Scientists laser-scanned this spire in 2009 to look for excessive erosion, but the study did not address how hoodoos form. Photo: NPS / Claire Crise.
One source for everything
Crise wanted to know how fewer freeze-thaw days would affect hoodoo formation. The park’s physical scientist, Tyra Olstad, told her there is no clear answer. Every book, paper and article about hoodoos that Crise found cites one unpublished source for the freeze-thaw hypothesis: Robert C. Lindquist’s 1980 University of Utah dissertation, Slope processes and forms at Bryce Canyon National Park. His ideas also appear in an earlier conference paper, “Genesis of the Erosional Forms of Bryce Canyon National Park.” The park’s own hoodoo page cites three works, and in each one’s bibliography the freeze-thaw idea is credited to Lindquist.
Crise had repeated the hypothesis in programs, visitor answers and materials for future rangers, because everything refers to it. Yet it was only a hypothesis in one person’s thesis, which she takes to show how little is known about how hoodoos form.
Research that is not about formation
According to Olstad, other work at the park has not tested the idea.
| Work | What it was |
|---|---|
| 2009 laser scans, Paul Jewell (University of Utah) and Juan Fernandez (University of Florida) | no report, only presentation slides; Olstad says that, as far as she knows, they told the park nothing new |
| May 2018 laser scan, NPS geologist Eric Bilderback | a proof of concept and a baseline survey for future change detection, with no geologic analysis |
| 2015 work by Jeffrey Moore (University of Utah) | the structural integrity of natural arches and some geohazard analysis |
| 2020 work by Tomsen Reed (Utah State University) | a rockfall hazard analysis of part of the park road |
Olstad says that Lindquist is the only person she knows of who has done a scientifically thorough study of what causes hoodoos, and that no peer-reviewed, published paper has examined the freeze-thaw hypothesis. She adds, “We do know the weather data.”
Fewer freeze-thaw days
A 2014 study by Bill Monahan and Nicholas Fisichelli found that temperatures in national parks over the past 20 years have already moved beyond their historical range of variability. Bryce Canyon has been monitored since the 1960s. Then it had 220 freeze-thaw days a year; in 2020, 170. The average high has risen about half a degree Fahrenheit, and the average low by seven degrees, so it is mostly the low temperatures that are disappearing. If the hypothesis holds, fewer new hoodoos are presumably being created.
Sunset Point, winter. Photo: NPS / Claire Crise.
Sunset Point, summer. Photo: NPS / Claire Crise.
What no one can say
Warming could reduce the hoodoos to unimpressive mounds of rock, or it might not, the article concludes: it is not known. Olstad calls it a delicate pitch to say that the park has an iconic landscape that is not fully understood, and that the processes creating it may be changing dramatically, but also an important message few people realize or want to admit.
Sources
- Claire Crise (seasonal ranger, Bryce Canyon National Park), “We Don’t Know What Will Happen to Bryce Canyon’s Hoodoos,” Park Science, Volume 36, Number 1, Summer 2022, National Park Service: https://www.nps.gov/articles/000/we-dont-know-what-will-happen-to-bryce-canyons-hoodoos.htm; rewritten in hubnx's own words.
Dans ces publicationsBryce Canyon National Park
Licence : CC0 1.0 (domaine public) · Adapté de www.nps.gov
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