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

Abstract

<jats:title>Abstract</jats:title> <jats:p>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.</jats:p> <jats:p> Explosive activity on 9 April and early on 10 April involved destruction of almost all of the 2020/2021 lava dome, <jats:italic>c.</jats:italic> 60% of the 1979 dome and formation of a 600 m diameter crater by 2pm UTC on 10 April. Following the initial explosion, plumes rose to altitudes of <jats:italic>c.</jats:italic> 15 km and pyroclastic density currents (PDCs), formed by column collapse, first occurred on 10 April, only after &gt;24 h 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. </jats:p> <jats:p>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).</jats:p> <jats:p> Volume estimates, using a range of techniques to constrain uncertainties, indicate that the bulk volume of tephra (fallout and PDC) is 1.19 × 10 <jats:sup>8</jats:sup> m <jats:sup>3</jats:sup> ± 20% making this a VEI 4 eruption. </jats:p>