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by Allen Glazner

DEVIL'S POSTPILE: Students examine grooves created when glaciers scraped across the top of the Devil's Postpile — a formation of basalt lava. Columns like this form when lava erupts from volcanic vents, cools, then shrinks and cracks into vertical columns. At right, the postpile's sheer wall face, which is 60 feet high. Allen Glazner, professor of geological sciences, shot these images on a field-seminar trip to Sierra Nevada and Death Valley.