Nature / Earth / Rocks and landscapes
How rock walls become Bryce Canyon’s hoodoos
Cracks, freezing water and unequal weathering help turn rock walls into isolated spires. The shape records what has been removed.
The tall, uneven rock spires at Bryce Canyon look like objects standing on the landscape. Their formation is easier to understand by asking what used to surround them. A hoodoo can be a remnant of a rock wall whose neighbouring material has been broken down and carried away.
First make the rock; then sculpt it
The National Park Service’s explanation separates three broad stages: sediment deposition, uplift, and weathering with erosion. The material that became the rocks accumulated in an ancient lake and floodplain setting. It hardened into several kinds of sedimentary rock, including limestone, dolostone and mudstone. Later uplift raised the landscape.
That history should not be confused with the age of an individual spire. Making the rock and making its present outline are different events.
NPS also draws a useful distinction between two everyday-looking words. Weathering breaks rock down. Erosion moves the broken material. A crack may weaken a wall, but removal of material is what opens space around the surviving rock.
From fin to window to spire
The park’s Life of Hoodoos wayside describes a sequence that makes the changing shapes easier to picture. As the plateau edge erodes, harder upper layers can protect softer rock beneath them. Narrow rock walls, called fins, remain.
Openings can develop within those walls. These are described as windows: there is still a connecting roof above the opening. As an opening enlarges and its roof gives way, parts of the wall become separate, irregular spires.
Try reading those shapes as relationships. A fin is still a connected wall; a window is a hole within one; a spire stands apart. This is a model of change, not a claim that every nearby formation is the same age or will follow an identical schedule.
Water works mechanically and chemically
The USGS account of Bryce Canyon’s geology explains how water enters cracks and freezes. Expansion during freezing puts pressure on the surrounding rock. Repeated freezing and thawing can help break it apart. The process is often called ice wedging or frost wedging.
Liquid water also matters. Weak acids in water can dissolve calcium carbonate, an important component of the limestone. The different materials and layers do not weather at the same rate, so the rock develops an uneven profile. Projecting ledges and narrower sections reflect differences in resistance, rather than a sculptor repeatedly cutting the same design.
These accounts emphasize ice, rain and differences within the rock. Simply saying that wind carved the spires would leave out the processes doing the explanatory work here.
Read a shape without inventing a clock
When studying a photograph, look for three things: connections between adjacent rocks, openings through a wall, and changes in width across layers. Those observations give you useful questions to bring to the geological explanation.
A single view does not tell you when a window opened or when its roof will fall. The sources describe processes; this article does not assign a lifespan or collapse prediction to a particular hoodoo.
References
Reading scope: the relevant NPS explanations and USGS sections on hoodoos and weathering of the Claron Formation. The two NPS pages are related interpretive sources, not separate scientific studies. No source photograph was reproduced or used for a measurement.
- National Park Service. (2021, September 4). Hoodoos. https://home.nps.gov/brca/learn/nature/hoodoos.htm
- National Park Service. (2023, September 22). Life of Hoodoos wayside. https://www.nps.gov/places/000/life-of-hoodoos-wayside.htm
- U.S. Geological Survey. (n.d.). Geology of Bryce Canyon National Park. https://www.usgs.gov/geology-and-ecology-of-national-parks/geology-bryce-canyon-national-park