Hoodoo Formation in Bryce Canyon
The Pink Member of the Claron Formation is largely composed of easily eroded and relatively soft limestone. When rain combines with carbon dioxide it forms a weak solution of carbonic acid. This acid helps to slowly dissolve the limestone in the Claron Formation grain by grain. It is this process of chemical weathering that rounds the edges of hoodoos and gives them their lumpy and bulging profiles.
In the winter, melting snow seeps into cracks and joints and freezes at night. The force of the expanding ice helps to erode the rock of the Claron Formation. Over 200 of these freeze/thaw cycles occur each year in Bryce Canyon. Frost wedging exploits and widens the nearly vertical joint planes that divide the Pink Member of the Claron Formation.
Internal layers of mudstone, conglomerate and siltstone interrupt the limestone horizontally. These layers are more resistant to attack by carbonic acid and they can therefore act as protective capstones of fins, windows and hoodoos. Many of the more durable hoodoos are capped with a type of magnesium-rich limestone called dolomite. Dolomite dissolves at a much slower rate, and consequently protects the weaker limestone underneath.
However, the same processes that create hoodoos will also eventually destroy them. In the case of Bryce Canyon, the hoodoos' rate of erosion is 2–4 feet (0.6–1.3 m) every 100 years. As the canyon continues to erode to the west it will eventually capture (in perhaps 3 million years) the watershed of the East Fork of the Sevier River. Once this river flows through Bryce Amphitheater it will dominate the erosional pattern; replacing hoodoos with a V-shaped canyon and steep cliff walls typical of the weathering and erosional patterns created by rivers. A foreshadowing of this can be observed in Water Canyon while hiking the Mossy Cave Trail. A diversion canal has been taking a portion of the East Fork of the Sevier River through this section of the park for over 100 years.
Read more about this topic: Geology Of The Bryce Canyon Area
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