Hoodoos are the kind of rock formations that make people take second and third looks. Many people think that these weirdly shaped rock spires that look like totem poles are made by wind erosion. Indeed, wind is a big force in sculpting the landscape, but Utah's hoodoos are formed by water. Rather than river water, these spikes are formed by ice.
Bryce Canyon is in the Paunsaugunt Plateau which receives approximately 100 inches of snowfall a year. It also experiences about 200 days of freezing and thawing when snow melts and runs into the joints and freezes at night. When water freezes it expands to form an ice wedge in the joint widening the space. As the ice wedge grows by more water leaking into the joint and freezing it will finally break the rock.
Where Bryce Canyon has massive armies of hoodoo formations, Zion National Park has isolated spires, with most of them located on the east side of the park.
"We have hoodoos in Zion, and they're formed differently than in Bryce Canyon," said Michael Plyler, director of the Zion Field Institute. "The cap layer is harder -- a mix of iron and magnanese over a shaft of softer material." The top of the shaft is protected from erosion, but not the sides.
In Bryce Canyon, added Plyler, snow melt and summer storms' water cascades down into the hoodoo-filled amphitheater. The water creates parallel ridges or fins of rock. Over time, frost wedging and erosion from rain erode the ridges into a series of hoodoos.
Hoodoo shapes are affected by the erosional patterns of alternating hard and softer rock layers. Harder or water-resistant layers will be wider and thicker than regular limestone.
Pullouts on the Zion-Mt. Carmel Highway give visitors many opportunities to look at the Zion Park hoodoos.
Visitors are urged to not approach the base of the hoodoo. According to park officials and geologists, the weight of a visitor can weaken the foundation and thereby the shaft of a hoodoo formation, accelerating the erosion process that will eventually make it fall over or disappear.