The earth is a phenomenal artist. I was reminded of this on a recent trip to Bryce Canyon in Utah…
Beneath a layer of fresh snow, the terracotta colored spires, known as hoodoos, reached their stony fingers upward, scratching at the clean winter sky. They are entrancing, these vestiges of a past time. Some stand close together; others apart – isolated and brooding. Every sculpture is different, beautiful in its rendering.
History Lesson (courtesy of information provided by the National Park Service):
This otherworldy portrait began to develop during the Cretaceous Period (which lasted from 144 million years ago to 65 millions years ago). It’s hard to picture now, but back then the ocean reached this region via a large seaway. The sea deposited sediments, which is what accounts for the oldest, lowest lying rock at Bryce.
The rock layer that forms the hoodoos is called the Claron Formation. This was formed during the Tertiary Period, between 55 and 35 millions years back, when rivers and streams deposited iron-rich limestone sediments in a lake that covered most of Western Utah.
The gnarled structures are the result two types of weathering processes.
1) Frost Wedging:
This happens when winter snowmelt seeps into cracks in the rocks and freezes as nighttime temperatures plummet below zero. Ice expands by roughly ten percent, forcing the cracks to widen even further. Repeated freezing, thawing and re-freezing can cause the rock to crack eventually.
Rainwater causes erosion. Additionally, the water is slightly acidic which further dissolves the limestone, rounding off the edges.
Interestingly, and as a reminder of the impermanence of all things, erosion will ultimately decimate the hoodoos. It’s estimated that in three million years erosion processes will gobble up the watershed of the east fork of the Sevier River. Water gushing through Bryce Canyon will eventually demolish the hoodoos, leaving behind a v-shaped canyon instead.
*All pictures courtesy Sarah Nicholson