Geology

Preludes to an Eruption

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Science  13 Oct 2006:
Vol. 314, Issue 5797, pp. 224-225
DOI: 10.1126/science.314.5797.224d

The cataclysmic 79 A.D. eruption of Vesuvius buried Pompeii and Herculaneum, and thanks to careful observation of the event by Pliny the Younger, marked the beginning of the science of volcanology. Several million people now live on volcanic deposits surrounding Vesuvius, and it is one of the world's most thoroughly monitored volcanoes. Thus, understanding the pre-eruptive behavior of this volcano is crucial. Morgan et al. have analyzed the concentration profiles of barium across crystals in the 79 A.D. ash; the profiles reflect the time during which diffusion occurred in the magma between an abrupt phase of crystal growth or dissolution and the eruption. Because of the strong temperature dependence of the diffusion rates, the profiles also constrain the magma temperature. The data suggest that the eruptive magma was recharged several times in the decades leading up to the cataclysmic eruption, most noticeably around 20 years before. Such recharge may explain the origin of a major earthquake in 62 A.D. A separate intrusion likely triggered the eruption. — BH

Geology 34, 845 (2006).

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