Eons for a Hoodoo
When we build man-made structures, like a bridge or building, we create by adding materials. But nature sometimes uses a different method, as in the case of the siltstone, mudstone, and limestone hoodoos found in Bryce Canyon National Park's amphitheater.
They are the result of subtraction rather than addition.
Hoodoos, which range from five to 150 feet tall, start their geological life in the same womb—one giant plateau. Individual hoodoos are carved out over eons through the chemical weathering process, as shown in this National Park Service illustration.
These unique structures are formed over centuries as grain after grain of sediment is whisked away by water and wind. When rain water combines with carbon dioxide, carbonic acid is produced, which further erodes the limestone.
Winter has a profound effect on the formation as well. Melting snow seeps into the rock cracks, and once night comes and the temperature drops, the water freezes, becoming ice. Water, as ice, expands, prying open the rock cracks (similar to a frost heave in the road).
The combination of 'frost wedging' and erosion give create these hoodoos, which are found in various parts of North America, but are most abundant in Bryce.
You can view these geological wonders on our Utah: Bryce and Zion Canyons trek. The view is other-worldly.
These hoodoos won't be here forever. Erosion occurs at a rate of about two to four feet per hundred years. Though the loss of these hoodoos will come long after our lifetime, this notion can make one feel an urgency to see a geological element that, in the long run, is a fleeting one.