Hoodoos and the Geology of Bryce Canyon

Spires of rock line the canyon edge mimicking a city skyline.

Bryce’s spectacular joodoos were carved by ice and wind. Photo © Judy Jewell.

As the top step of the Grand Staircase, Bryce’s rocks are young by geologic standards. The park’s Pink Cliffs lie on top of older rock layers, which are exposed in stair-step form as you head south toward the Grand Canyon.

This fantastic landscape got its start about 60 million years ago as sediment dropped to the bottom of a large body of water, named Lake Flagstaff by geologists. Silt, calcium carbonate, and other minerals settled on the lake bottom, then consolidated and became the Claron Formation—a soft, silty limestone with some shale and sandstone.

Lake Flagstaff had long since disappeared when the land began to rise as part of the Colorado Plateau uplift about 16 million years ago. Uneven pressures beneath the plateau caused it to break along fault lines into a series of smaller plateaus at different levels known as the “Grand Staircase.” Bryce Canyon National Park occupies part of one of these plateaus, the Paunsaugunt.

The spectacular Pink Cliffs on the east edge of the Paunsaugunt Plateau contain the famous erosional features known as hoodoos, carved in the Claron Formation. Variations in hardness of the rock layers result in these strange features, which seem almost alive. Water flows through cracks, wearing away softer rock around hard erosion-resistant caps. Finally, a cap becomes so undercut that the overhang allows water to drip down, leaving a “neck” of rock below the harder cap. Traces of iron and manganese provide the distinctive coloring. The hoodoos continue to change; new ones form and old ones fade away. The plateau cliffs, meanwhile, recede at a rate of about one foot every 50-65 years; look for trees on the rim that now overhang the abyss. Listen and you might hear the sounds of pebbles falling away and rolling down the steep slopes.

Hoodoos

Although many visitors assume that wind shaped Bryce Canyon’s hoodoos, they were, in fact, formed by water, ice, and gravity, and the way those elements and forces have interacted over the years on rocks of varying hardness.

When the Colorado Plateau uplifted, vertical breaks—called joints—formed in the plateau. Joints allowed water to flow into the rock. As water flowed through these joints, erosion widened them into rivulets, gullies, and eventually deep slot canyons. Even more powerful than water, the action of ice freezing, melting, then freezing again, as it does about 200 days a year at Bryce, causes ice wedges to form within the rock joints, eventually breaking the rock.

Bryce Canyon is composed of layers of limestone, siltstone, dolomite, and mudstone. Each rock type erodes at a different rate, carving the strange shapes of the hoodoos. The word hoodoo derives from the same sources as voodoo; both words are sometimes used to describe folk beliefs and practices. Early Spanish explorers transferred the mystical sense of the word to the towering, vaguely humanoid rock formations that rise above Southwestern landscapes. The Spaniards believed that Native Americans worshipped these statue-like “enchanted rocks.” In fact, while early indigenous people considered many hoodoo areas sacred, there is no evidence that they worshipped the stones themselves.


Excerpted from the Fifth Edition of Moon Zion & Bryce.

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