Bryce Canyon Geology, Rock Formations

Visitors drawn by the unique rock formations have made Bryce Canyon National Park a destination location. Over the past sixty million years, changes in climates and massive geological shifts in the earth have created this wondrous world of extraordinary rock formations. A visit to Bryce Canyon National Park gives the visitor a whole new look at the science of geology.

Sedimentation
For 60 million years, a great seaway extended northwestward into this area, depositing sediments of varying thickness and composition as it repeatedly invaded, retreated, and then re-invaded the region. Retreating to the southeast, it left sediments thousands of feet thick. Their remnants form the oldest, lowest, gray-brown rocks at Bryce Canyon.

Between 66 and 40 million years ago, highlands to the west eroded into shallow, broad basins. Iron-rich, limy sediments were deposited in the beds of a series of lakes and streams. These became the reddish rocks of the Claron Formation from which the hoodoos are carved.

Differential Erosion
Water erodes rock mechanically and chemically. Scouring, abrading, and gullying occur when fast-moving water scrapes its silt, gravel, and rock debris against firmer bedrock. Slow-moving or standing water enters minute rock pores and dissolves cements holding the rock together.
Along the plateau rim, conditions are optimal for erosion. Its steep slope increases water speed and energy. Faults and joints from ancient compression forces influence erosion patterns. Freezing and thawing loosen slope surfaces. Debris carried by runoff, scours softer rock and creates gullies; harder rock remains as fins.

As gullies widen to canyons, fins become exposed to further erosion along vertical cracks. In winter, freezing water expands within cracks to peel off layers and carve vertical columns.

More Current Geological Conditions
Current yearly weather cycles aid the process that helps to form a hoodoo. In Bryce Canyon, it freezes at night approximately 360 days of the year. The freeze and thaw cycle loosens the slope surface, allowing debris to be sloughed off by water run-off.

When you are hiking among the hoodoos, look closely and you will see vertical cracks. The material carried away works on the softer rock to create gullies, and ultimately canyons. The hard rock that was left behind is further eroded along its vertical cracks, again subjected to the freeze - thaw cycle carving the hoodoos.