Where on (Google) Earth #18
Sagan has no blog, so I'll post 18. Next one is somebody else, though. No hints. Please also list the order in which the various features cross-cut.
Gazing off into space
6 hours ago
Thursday, June 21, 2007
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5 comments:
42°57'N 89°40'E
now I retire from the fray.
Mind sharing, or at least describing the geology a bit?
I'm not Sagan, and I wouldn't have figured it out without his lat/long. But here's what I see (especially zooming out)...
The area is in northern China, a little south of the Mongolian border, northeast of the Tarim Basin. It's in a valley between a number of WNW-ESE trending mountain ranges. The big alluvial fans in the northern part of the photo drain one of those ranges.
The alluvial fans feed into three canyons that cut across the layers in the middle of the photo. I'm using google maps rather than google earth (no high-speed internet from home), so I can't get an oblique view, but it looks like an anticline - one that I think has grown after the stream channels developed, so the downcutting of the stream has kept pace with the growth of the anticline? (If that's true... I want to go on a field trip! Very cool.)
Each one of the streams feeds another alluvial fan to the south of the fold.
There are sand dunes in the SE corner of the photo. If you zoom out, you can see that they are part of a larger erg.
(This is a really cool game.)
Tectonite, do you want to post number 19? If so, just link it from here when you get it up.
You can wait a few days to find a good spot, if you like. There is no hurry.
And if you get a chance to look around, you should see that there are nearby areas where the valley floor is uplifting, but the erosion hasn't yet cut into the anticlines.
How do you know to look in NW China, though?
Well, I wasn't the one who figured out it was in NW China - sagan was. I just typed his (?) lat/long into Google Maps and backed out until I could see the Tarim Basin and the border with Mongolia.
But I guess there were some clues - it's tectonically active, it's dry, and the structures strike E-W. That would make me look at the Alpine-Himalayan chain rather than in Andes. But I'm not sure I would have zoomed in all that quickly.
I posted a new image: Where on (Google) Earth #19.
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