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8 September 2017
Big earthquake in southwestern Mexico, M8.1
The M8.1 southwestern Mexico earthquake is discussed and placed in context.
Friday fold: Ptygmatic folding in gneiss
I was transferring some samples into my structural geology cabinet last week when I found this beautiful ptygmatic (“intestine-like”) folded quartz vein. I thought it deserved some wider circulation. I can’t recall where it came from, but it’s beautiful, with a train of a dozen or so isoclinal folds. So I made the digital media you see below. Enjoy! Here’s a GIGAmacro of the sample (you need Flash enabled to …