Saturday, May 16, 2015

Geo-challenge: two landforms, one river

What are these landforms and where?  Which river is “involved” in both?  You can respond via Comments below.  In a few days I’ll post answers in a Comment and tweet.

I think (and hope!) this geo-challenge will be easier than the last one, which featured the escarpment side of Comb Ridge.  The dip-slope side, with outcrops of Navajo sandstone, is the more familiar view.  More explanation here.

UPDATE:
Readers got it:  1) west flank of Raplee Ridge, a small anticline – crossed by the San Juan River; and 2) incised meander at Goosenecks State Park – cut by the San Juan River.  Both are in southeast Utah.
Click on image to see details.
  

7 comments:

  1. The upper one appears to be Comb Ridge, where the San Juan River has cut a water gap,and the lower one (which should be a dead give-away to most US geo types) is Goosenecks State Park, where the San Juan River has cut an exquisite series of incised meanders.

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    1. Two out of three, and the third very close. See Comments below. Thanks!

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  2. That is one of the goosenecks of the San Juan, but the monocline is Raplee Ridge which is flexure which opposes Comb Ridge to the west.

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    1. Yep! San Juan cutting through Raplee Ridge (downstream from Comb Ridge) and a gooseneck further downstream.

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  3. When I saw this teaser from you I had no idea what the answer was. I still don't, but the image stayed with me and today in one of our Sunday newspapers I saw what i thought was a very similar formation, Dead Horse Point in Utah. See the image here: http://yhoo.it/1HlPRmb I would be interested to know if the geology is broadly similar to your featured landscape.
    All the best :)

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    1. Yes! ... in both places the rivers are entrenched (see http://en.wikipedia.org/wiki/Entrenched_river) with spectacular entrenched or incised meanders. The rivers kept cutting down (didn't move) while the Colorado Plateau was gradually uplifted. Neat photo!

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  4. Answers added as an Update above.

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