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15 February 2010
Shear bands in amphibolite
Check out these cool structures in one of the amphibolite bodies exposed along the Billy Goat Trail (C&O Canal NHP, near Potomac, Maryland): Those are shear bands — basically small shear zones that are discretely localized within a larger body of less-deformed rock. Note the grain-size reduction visible in the shear bands, their dextral sense of offset, and their induration (making them more resistant to the forces of weathering and …