Dynamics of tephra fallout and column collapse during Plinian eruptions of Mt. Pelée volcano (Lesser Antilles): The 2.5 ka cal BCE P5 eruption

Mt. Pelée volcano in Martinique (Lesser Antilles) has undergone volcanic unrest since 2019 and an increase of alert level to yellow (vigilance) in 2020. Historical records and field studies show that this volcano has produced numerous dome-forming and sub-Plinian to Plinian eruptions over the last 25 kyr. The 2.5 ka cal BCE P5 eruption dispersed lapilli and ash across the northern part of Martinique. Here, we present field data on tephra dispersal and grain-size distribution to estimate the eruption source parameters and reconstruct the dynamical evolution of the eruption. Our results show that after a short opening phase, the P5 Plinian eruption formed a 26 km-high stable column with a northeastern dispersal axis. The total volume of the eruption is estimated to be 0.39 ± 0.03 km³ DRE making P5 a VEI 4 event. The mass eruption rate increased from ≈ 1.1 × 10⁸ kg s⁻¹ to ≈ 4.8 × 10⁸ kg s⁻¹ leading to column collapse and the formation of pyroclastic density currents on the flanks of the volcano. The transition from stable column to collapse occurred at conditions well predicted by a 1D model of volcanic plumes and confirms that this eruptive scenario is recurrent at Mt. Pelée volcano over the last 5 kyr. The tephra dispersal of the P5 eruptive products reinforces the accuracy of the current hazard map and provides volcanological constraints to better assess volcanic hazards in the Lesser Antilles.