Abstract

Mount Pelée volcano (Martinique) is one of the most active volcanoes in the Lesser Antilles arc with at least fifteen magmatic events in the last 5,000 years, including the deadliest eruption of the twentieth century in 1902. Our knowledge of the eruptions older than 5 ka is however very limited, thus reducing our capacity to predict the dynamics of future eruptions at Mount Pelée.

Two new extensive field studies performed in 2017 and 2019 in Martinique combined with carbon-dating measurements allow us identifying six new eruptions in the past 24 ka cal BP, including four Plinian and two Pelean eruptions. We reconstruct the dynamical evolution of the newly discovered Plinian eruptions of Bellefontaine (13.5 ka cal BP), Carbet (14 ka cal BP) and Etoile (21.5 ka cal BP) whose great interest stems from their unusual southward dispersal axis encompassing areas that are considered to be safe in current hazard maps. Using the 2-D ash dispersion HAZMAP model, we identify peculiar atmospheric circulations associated to a modification of the subtropical jet-stream path producing northerly winds over Martinique and thus spreading ash towards the most populated areas of the island.

This integrated approach, combining field studies and model predictions, allows us to build new volcanic hazard maps for tephra fallout in Martinique. Our method is based on 16 eruptive scenarios, consistent with the data retrieved from our stratigraphical records. Each scenario considers a different pair of deposit mass and mass discharge rate, and is given a probability of occurrence calculated from the complete eruptive history of the volcano. We use the ERA -5 database to consider the daily variability of winds. These new probability maps, as well as the predicted range of damages that could be expected at key infrastructures in Martinique, will be useful to revisit the emergency procedures as the volcanological observatory (OVSM) recently raised Mount Pelée volcano on alert level 2.