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13 April 2012

Friday folds: Turpan Depression

Rob Simmon of NASA’s Earth Observatory is the source for today’s Friday folds. Last week, he tweeted this image to me: That’s a excellent example of the outcrop pattern of a more or less horizontal outcrop of folded rock. To the north is a synform (notice that where streams have eroded it, the bull’s-eye pattern takes a notch inward toward the center of the structure), and to the south, a …


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19 February 2012

Plane views

A few scenes out the left side of the airplane from when I flew from El Paso to Houston a week and a half ago… Sand dune field overprinting desert vegetation and human roadways: Outcrop pattern of horizontal strata (tracing out the contours of this hill), and the weird geometry of human road systems: More contour-hugging outcrops of horizontal strata, and a vertical joint set: Same thing: Bajada (apron of …


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29 December 2010

GoSF9: Pleistocene dunes

The penultimate episode of Callan’s more-than-a-week-long series on the geology of the San Francisco region: today we briefly visit the sand dunes that covered San Francisco Peninsula during the Pleistocene.


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