How Mole Hill in Virginia became a mountain is an old story, but not as old as some geologists think. The reason for that has to do with volcanoes—and may help explain why the U.S. East Coast, so long removed from geologic upheaval compared with the West, still suffers from relatively powerful earthquakes like the one that shook Mineral, Va., and much of the East Coast, in 2011.

Five years ago or so, newly minted professor of geology Elizabeth Johnson needed something for her undergraduate students at James Madison University to study on field trips.  Locals suggested the unusual geology of Mole Hill, just a few kilometers from campus, where one could find black obsidian (a superhard rock glass formed when magma cools quickly) or rocks that when cracked open looked as pure white as newfallen snow thanks to the carbonate minerals inside.

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