Characterization of the Tephra deposits produced during the ongoing eruption of Soufriere Hills Volcano, Montserrat - WI

Soufriere Hills volcano is one of the eruptive centers of Montserrat, an island situated in the northern part of the volcanic insular arc of the Lesser Antilles. In 1995, after a long period of quiescence, the volcano started again its activity that is still carrying on. The activity of the volcano is divided in several styles: phreatic explosions, characterized by sudden release of heated ground-water; andesitic-dome growth with dome collapse episodes with associated pyroclastic flows; magmatic explosions, associated with fountain collapse pyroclastic flows, event of catastrophic sector collapse, with associated explosive dome disruption and pyroclastic density currents.

The volcanic activity is characterized by the production of very destructive events, have caused the burial of the capital Plymouth in 1995 and rendered the south part of the island totally inhabitable. The Soufriere Hills volcano is one of the most monitored volcanoes in the world. The Montserrat Volcano Observatory takes daily detailed measurements and reports on the volcanic activity in order to prevent risk for the population.

The aim of this project is the characterization of the tephra fall deposits of several volcanic explosions of the Soufrière Hills volcano, in order to investigate on the parameters that influence the settling process of volcanic particle. In details we want to understand how the shape of the particles influences the terminal fall velocity, and how this influence is reflected on the distribution of the tephra products on the surface. The characterization of the deposits will be done completing isopach and isopleths maps, and calculating the total grainsize distribution using the Voronoi tessellation. The characterization of the volcanic particles will be done using granulometric and morphologic analisys of the samples, through laser diffraction techniques (for determinating the grainsize distribution) and image analysis, and using some physical theoretical models for the determination for their terminal velocity (Wilson and Huang, 1979; Ganser, 1992; Dellino et Al., 2005).