Across much of the Southwestern U.S., through Utah, Arizona, and Nevada, there is an astonishingly beautiful layer of sandstone, exposed in places like Zion National Park, Capitol Reef National Park (both in Utah), and the Grand Canyon. But a lot of people I suspect don't realize how many other really astonishingly beautiful exposures there are elsewhere. For example, this is Red Rock Canyon, a few miles west of Las Vegas. (Yes, we're the only people in history that went to Las Vegas to visit a museum, and see geology.)
Some of these pictures may look a bit odd. Most of these rocks were backlit, because it was late afternoon. Consequently, I had to adjust contrast and exposure to get a reasonably accurate rendition of the color of the rocks--but often at the cost of fading the sky.
By the way: even when you click through, you are seeing low resolution versions of these pictures. If you are someone who wants a high resolution version for some purpose (like the request to reprint that I received from a Chinese biology textbook publisher a while back), I can provide them.
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Here my wife is up close to one of the easier to get to sections of exposed sandstone layers.
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What's with the red and black? This is a sandstone rich in iron, and depending on which oxidation of iron, you get either red, ferric oxide) or black, ferrous oxide. (For those who took chemistry after the Dark Ages ended, substitute iron(II) or iron(III) for ferrous and ferric.)
Of course, the amount of iron in the sandstone will sometimes determine how intense of a color you get, as this astonishing striping shows.
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One of the more startling aspects of these sandstone formations across the Southwest is that they weren't laid down under water--they are fossilized sand dunes, resulting in some truly wild jumbles.
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As always, I would love to make a living as a writer. Having discovered that writing about public policy isn't one of those methods, feel free to hit the PayPal button to encourage me to be a travel writer!
I'm not so sure that dark layer is due to oxidation. Native American petroglyphs are carved in that layer. Some petroglyphs have been estimated to be 4,000 to 8,000 years old. There are no signs of the black layer returning to places where it was chiseled away. Whatever made that layer is apparently not happening now. I heard about the "black mat" layer that is found throughout North America. I wonder if the same event that created the "black mat" layer also burned outer surfaces of exposed rocks? Just a theory. That layer is strange, I first saw it in Red Rock Canyon, Nevada, near Las Vegas. Last summer I noticed the same layer on white rocks on the Hopi reservation, hundreds of miles East of Vegas. I can send you the photos if you wish. Anyway, thanks for posting your photos.
ReplyDeleteEvidence for an extraterrestrial impact 12,900 years
ago that contributed to the megafaunal extinctions
and the Younger Dryas cooling
http://www.pnas.org/content/104/41/16016.full.pdf