Canyonlands

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Early morning view from the top of Mesa Arch to the surrounding desert lowlands, Canyonlands National Park, Utah. (© 2014 Jonathan Gewirtz / jonathan@gewirtz.net)

11 thoughts on “Canyonlands”

  5. Here’s an interesting thing I’ve learned about places that are comprised of thick beds of sedimentary rock, their shape and how it changes over time, what’s called the geomorphology, is controlled by regional joints suites that are essentially at right angles to each other. Notice you don’t have a random distribution of directions of the cliff faces, they’re orthogonal and sub-parallel over the entire region. You can see some of those joints on the surface of the mesa where this photo was taken.

    The joints act as pathways for water. When rain falls through the air it picks up small amounts of carbon dioxide, which goes into solution forming a mild carbonic acid. All rain, everywhere, is acid rain and always has been. The acid rainwater flows preferentially into the rock joints dissolving the calcium carbonate mortar that is binding the rock together. Over time this divides the rock into blocks. In the winter, the water saturated joints freeze, and since frozen water has a volume about 10% larger than liquid, it drives the blocks apart or shatters them. That process, called ice wedging and frost shattering, is why all high mountain slopes are covered in piles of rock debris called talus. The talus slides down the steep faces and accumulates in fan or cone shaped areas at the base. The base of the cliff faces in many of these canyons are also talus slopes.

    Nice photo. Shots like that are harder to get right than it seems like it should until you try it yourself. Nice work.

  6. That’s a beautiful photo. I really like the clouds. The left to right direction of the sunlight to the dark clouds gives the illusion of motion, at least to me.

    And Michael, thanks for the quick geology lesson. I always been fascinated with the way those processes work and the results.

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