The recent pumice eruptions of Mt. Pelée volcano, Martinique. Part II: Grain-size studies and modeling of the last Plinian phase P1

Abstract

Abstract Some aspects of the last pumice eruption P1, recorded at Mt. Pelee volcano, Martinique, and dated at 650 years B.P., are quantified. During this event, Plinian falls were followed by pumice flows channelled by the valleys. Plinian deposits crop out over the entire Mt. Pelee massif and significant volumes fell upon the ocean. Grain-size studies of the fall deposits show a median (Md Φ) which generally ranges from −2.25 to −3.8 Φ, and a sorting coefficient (σ Φ) of between 1.33 and 2.75. The main volcanological parameters are: Tmax (thickness) up to 15 m, F (fragmentation) of 10 wt.% of clasts less than 1 mm in size, and D (dispersal) of about 900 km2. The total volume of the tephra is estimated at 0.95 km3 and the duration of the eruption at 1.5–3 h, which liberated a total thermal energy of 0.4 × 1025 ergs with a mass eruption rate of between 3.8 and 7.0 × 107 kg s−1. The column height is calculated to be 20–22 km, and the initial muzzle velocities between 230 and 310 m s−1 for blocks 0.4–0.7 m in diameter. These parameters suggest that the eruption was a relatively small Plinian eruption.