Explosive sequence of La Soufrière St Vincent April 2021:Insights into drivers and consequences via eruptive products

This paper forensically reconstructs the timings, impacts and processes that drove the sequence of explosive eruptions of La Soufrière, St Vincent in April 2021 using a combination of field-based stratigraphy and textural dissection of the deposit character together with contemporary visual observations. Explosive activity on 9th and early on 10th April involved destruction of almost all of the 2020/2021 lava dome, ∼ 60% of the 1979 dome and formation of a 600 m diameter crater by 2pm UTC on 10th April. Following the initial explosion, plumes rose to altitudes of ∼15 km and pyroclastic density currents (PDCs) formed by column collapse, first occurred on 10th April, only after > 24hrs of explosive activity. Dense PDCs reached the sea only in the Larikai and Roseau Valleys, and dilute PDCs were restricted to within 2.5 km of the Summit Crater rim. The tephra fallout deposits are stratified, composed of numerous layers of both lapilli-rich and ash-rich layers, which we have grouped into at least 7 Units, based on their common characteristics (Units 1 to 7). Volume estimates, using a range of techniques to constrain uncertainties, indicate that the bulk volume of tephra (fallout and PDC) is 1.19 x 108m3 +/− 20% making this a VEI 4 eruption. Supplementary material at https://doi.org/10.6084/m9.figshare.c.6474317