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Crystal clocks

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Science  18 Nov 2016:
Vol. 354, Issue 6314, pp. 822-825
DOI: 10.1126/science.354.6314.822

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Summary

Crystals in volcanic rocks contain clocks that offer clues to the volcano's plumbing and past behavior. The technique, called diffusion chronometry, is catching on among volcanologists. It depends on understanding how the crystals grew out of a magma soup deep underground, accreting layers that bear witness to pulses of magma. By measuring the amount of chemical smudging at the interfaces between the layers, scientists can calculate the time the crystal sat below ground between magma pulses. Already, the few researchers adept at using diffusion chronometry have found that magma can tear through the crust at searing velocities, and that volcanoes can gurgle to life in a geologic instant. Instead of taking centuries or millennia, these processes can unfold in a matter of decades or years, and sometimes even months. The results help explain why geophysicists haven't found simmering pots of liquid magma beneath volcanoes, and why some eruptions are more violent than others.