The recent Plinian explosive activity of Mt. Pelee volcano (Lesser Antilles): The P1 AD 1300 eruption

Plinian explosive eruptions represent a major volcanic hazard in the Lesser Antilles Arc that must be carefully assessed based on reconstructions of past activity. The present study focusses on a detailed time evolution of the P1 eruption (AD 1300) at Mt Pel,e volcano (Martinique). After an initial dome-forming stage, a Plinian phase commenced. The P1 Plinian-style sequence is mostly a pumice fall deposit with an inversely graded base, interbedded with a surge deposit, and overlain by final flow/surge deposit. Field data on deposit dispersal, thickness, and grain-size distribution are used together with physical models to reconstruct the dynamical evolution of this eruption. We find that the mass eruption rate increased from 2x10(7) to 9x10(7) kg s (-aEuro parts per thousand 1), producing a 19-22-km-high Plinian plume, initially stable but which ultimately collapsed to form a similar to 1.3-km-high fountain. Empirical models of deposit thinning suggest that the minimum volume of pyroclastic deposits is 0.15 km(3), about 25 % that previously estimated. Published data on magmatic water contents in glass inclusions are used together with mass discharge rates to elucidate the mechanisms leading to column collapse. Conditions at the base of the column were close to the plume/fountain transition soon after the Pelean/Plinian-style transition due to the competing effects of increase in both gas content and mass discharge rate. After a short stage of partial collapse, the column underwent a total collapse due to an increasing discharge rate.