Dynamics of the 1902 Eruptions of Montagne Pelee Determined from Size, Shape, and Textures of Vitric Pyroclasts

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This project will investigate juvenile glassy tephra from the nuee-ardente deposits produced the cataclysmic eruptions on Montagne Pelee in 1902, as a basis for interpretation of the role of hydrovolcanism in the eruption dynamics of this cycle of activity. The research is undertaken specifically to provide sharper insights into the physical processes responsible for such large and devastating explosive eruptions. Electron microprobe (EMP), scanning electron microscope (SEM), image analysis, and size distribution analysis will be the main techniques used to investigate tephra deposits left by the passage of successive nuees ardentes or sediment gravity flows in the vicinity of St. Pierre, Martinique. Internal and surficial textural information observed on juvenile vitric fragments from the nuee ardente deposits will shed light on (1) processes of magma vesiculavesiculation and fragmentamentation as a result of sion of juvenile magmatic volatiles; (2) the role and timing of hydromagmatism during the eruption; (3) the genesis of nuee ardentes; and (4) the mechanics of particle-particle interaction during transtransport and deposition of nuee-ardente tephra. Grain size distribution analysis using the new model of sequential fragmentation and transport will allow the identification of maturity of fragmentation and transportation processes to be evaluated for various parts of the nuees at various distances from the source. This information should be extremely useful in the evaluation of volcanic hazards at volcanoes with a history of large expolosions such as those of Montagne Pelee.