Video
Desert Varnish
Transcript
Hello, my name is Jenny Eberlein, I am an Interpretive Ranger here at Zion National Park. Welcome.
Zion is home to some of the tallest sandstone cliffs in the world. Large sections of the sheer rock are often coated with mysterious and beautiful colors. Streaks and panels of black paint the canyon walls, and are often asked about. The answer about how this patina forms, relates back, like many processes here, to water.
Some of these streaks reveal the locations of ephemeral waterfalls. Rainfall of the summer monsoon, runs off the slick rock and pour from the tops of the cliffs, then the falls disappear as fast as they emerge. These falls leave the rock face wet. Large areas can also become moistened simply by humidity. Once the surface is wet, windblown particles, such as dust, soil, or plant material, stick to the desert varnish and become incorporated into the rock face. What happens after incorporation is still a bit of a mystery.
Scientists believe that the mixture of particles provides life to bacteria, which then produces manganese oxide as a waste product, causing the varnish to turn black. The microscopic processes of this film can take thousands of years to build up to the thickness of a single sheet of paper. During this time, this biotic process is surviving extreme temperatures from below freezing in the winter, and up to 130 degrees Fahrenheit on the rock face during the summer. What is more interesting is scientists recently discovered this black patina has layers, much like the rings of a tree. Seen under a high-powered microscope, dark bands indicate periods of wetter, cooler weather, and lighter bands indicate periods of drier, hotter weather. However, these layers still hold secrets that we have yet to unlock.
All across the canyon, nature is ever at work as the artist. Varnish forms as black patinas on the immense sandstone walls. But the microscopic formation of desert varnish may be best left undiscovered. Perhaps part of the beauty is, not knowing exactly what causes this coloration. Perhaps part of the enjoyment is the mystery which paints the walls of Zion.
Description
Uncover the mystery behind the black streaks that paint the walls of Zion with Park Ranger Jenny Eberlein.
Duration
2 minutes, 16 seconds
Credit
NPS
Date Created
08/14/2012
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