Abstract This paper provides an overview of the eruption of La Soufrière Volcano on the island of St Vincent which occurred between 27 December 2020 and 22 April 2022. It sets the stage for the 17 papers included in this Special Publication that showcase the initial scientific findings arising from analysis of the crisis. Here we present a chronology of the eruption and discuss the key findings from these papers while underscoring the areas for which further research is needed. The detailed account of the eruption offers several lessons for volcanic crisis management and provides insights into the most effective communication process through this type of crisis. It highlights the need for and benefits of planning and preparedness activities prior to an eruption as well as of long-term engagement with disaster management officials and at-risk communities. The value of partnerships both within the island and with external collaborators was shown to be critical as was the use of a multiparametric dataset to assess the course of the eruption. We contend that the papers contained in this publication provide key insights into the mechanisms by which volcanic eruptions can impact populations at risk. The suite of analyses and data have generated a canonical dataset that can provide the framework for new advances in understanding the causes and consequences of varying eruptions worldwide.

Abstract The 2020–21 eruption of La Soufrière, St Vincent consisted of two distinct phases. The initial, effusive phase was characterized by the extrusion of a small lava dome inside the 1.5 km wide Summit Crater, and was followed by a violent explosive phase. Growth and evolution of the lava dome was monitored by visual observations and photogrammetry using imagery acquired from fixed-wing aircraft, helicopters and consumer-grade unmanned aerial vehicles. Additional monitoring was provided by satellite multispectral and radar imagery. Following the emergence of lava at the surface on 27 December 2020, volume and growth rate calculations showed the extrusion occurred at a steady rate of c . 1.8 m 3 s −1 and c . 16–19 × 10 6 m 3 of lava was extruded. The initial near-perfect hemispherical dome transitioned into a dome with a more elliptical footprint, eventually, evolving into a coulée-like feature with two lobes. The dome was destroyed by the onset of explosive activity on 9 April 2021.

Abstract The 2020–21 eruption of La Soufrière, St Vincent began with extrusion of a viscous lava dome, which was destroyed upon transition to a major explosive phase. Here we present petrological data to reconstruct the processes leading up to these events. Bulk-rock SiO 2 contents range from 52.8 to 55.4 wt%, classifying the lava and the subsequent scoria as basaltic andesite, the latter being slightly more mafic. Macrocrystal chemistry and modes (plag–cpx–opx–tmt–ol) and crystallinity (45–50 vol%) are largely identical for both phases of the eruption. Pyroxenes are homogenous and precipitated mostly from andesitic melts. Conversely, plagioclase shows strong normal zonation resulting from magma ascent and stalling at multiple crustal levels. Clinopyroxene thermobarometry reveals that crystallization predominantly took place between 8 and 13 km depth at temperatures of 997 − 35 + 18 ∘ C . A lack of evidence for mafic recharge and changes in volatile content and the omnipresence of xenoliths, suggests pre-eruptive destabilization of an andesitic–dacitic melt pocket that disrupted and entrained antecedent mush. Olivine diffusion profiles show that this interaction preceded the onset of eruption. Low dissolved sulfur contents (≤270 ppm S) place constraints on the total SO 2 gas release. Melt–mush disruption appears to be a dominant driver of eruptions at La Soufrière. Supplementary material: Supplementary figures and tables, as well as electronic data tables, are available at https://doi.org/10.6084/m9.figshare.c.6484877

Abstract Following a month of unrest in June–July 2019 and 3 months of effusive activity from late December 2020 to March 2021, La Soufrière volcano, St Vincent, transitioned to a 2-week period of explosions on 9 April 2021. During initial unrest, there was one working seismograph station on the volcano, providing the only information for tracking fluctuations in seismicity. Subsequently, full capability for locating volcanic earthquakes was achieved on 27 January 2021. Because events prior to this did not have reliable locations, unconventional data tracking approaches were adopted for assessing unrest evolution. Holistic inferences, suggested by combining these novel analyses with decades of knowledge of Lesser Antilles volcanoes, provided punctual evidential support for assessing the possibility that unrest could culminate in explosive activity. However, this case history is not offered as a paradigm for minimalist seismic monitoring at active volcanoes, notwithstanding that information gains were possible. This said, evaluations of seismic moment release, using event duration magnitudes as proxies for moment magnitudes, allowed the magma volume intruded or activated in the volcano to be estimated: 68 ± 14 × 10 6 m 3 dense rock equivalent (DRE) magma; this is a value remarkably similar to a geological estimate of total erupted volume (71 ± 14 × 10 6 m 3 DRE), with matching uncertainties.

Abstract In the West Kunlun Mountains, four volcanic fields (Kangxiwa, Dahongliutan, Qitaidaban and Quanshuigou) are distributed along the Dahongliutan fault, which is c. 180 km long. Based on field investigations, chronological measurements and geochemical analysis of some volcanic fields, the results of geological, geochemical and geophysical research in previous studies in the corresponding study areas are summarized. The volcanic activities in these areas were mainly effusive eruptions, explosive eruptions and phreatomagmatic eruptions. In this study, we discovered the Qitaiyanhu volcanic field for the first time and determined that the 14 C age of the lacustrine strata underlying the Qitaiyanhu lava flows is 13.110 ± 0.04 ka BP, indicating that there may still have been volcanic activities in the late Pleistocene and even the Holocene in the Dahongliutan fault area. Base surge deposits, which are the products of the interaction between magma and water, were found in the Kangxiwa volcanic field. The four shoshonitic rock fields of Kangxiwa, Dahongliutan, Qitaidaban and Quanshuigou are likely to be products of different evolution stages from the same magma source area. The magmatic origin of these volcanic fields may be related to the upwelling of the asthenosphere, triggered by the collision between the Indian and Tarim plates.

Abstract Since Jurassic time (c. 200 Ma), Antarctica has had a greater diversity of volcanism than other southern continents. It includes: (1) voluminous mafic and felsic volcanism associated with the break-up of Gondwana; (2) a long-lived continental margin volcanic arc, including back-arc alkaline volcanism linked to slab rollback; (3) small-volume mafic alkaline volcanism associated with slab-window formation; and (4) one of Earth's major continental rift zones, the West Antarctic Rift System (WARS), with its numerous large alkaline central volcanoes. Several of Antarctica's volcanoes are still active. This chapter is a review of the major volcanic episodes and their principal characteristics, in their tectonic, volcanological and palaeoenvironmental contexts. Jurassic Gondwana break-up was associated with large-scale volcanism that caused global environmental changes and associated mass extinctions. The volcanic arc was a major extensional arc characterized by alternating volcanic flare-ups and lulls. The Neogene rift-related alkaline volcanism is dominated by effusive glaciovolcanic eruptions, overwhelmingly as both pāhoehoe- and ‘a‘ā-sourced lava-fed deltas. The rift is conspicuously poor in pyroclastic rocks due to the advection and removal of tephra erupted during glacial intervals. Volcanological investigations of the Neogene volcanism have also significantly increased our knowledge of the critical parameters and development of the Antarctic Ice Sheet.

Abstract Understanding the behaviour of fluids in hydrothermal systems is a key factor in volcano monitoring. Measuring gas emissions in volcanic areas is strategic for detecting and interpreting precursory signals of variations in volcanic activity. The role of radon as a potential precursor of earthquakes has been extensively debated. However, radon anomalies appear to be better suited to forecast eruptive episodes as we know the loci of volcanic eruptions and we can follow the evolution of volcanic activity. Radon mapping is an effective tool in assessing diffuse and concentrated degassing at the surface. We hereby summarize the in-soil radon emissions collected worldwide and further discuss a collection of data on our key targets. These are closed-conduit and open-conduit volcanoes: Vesuvius (Italy) and La Soufrière (Guadeloupe, Lesser Antilles), Stromboli (Italy) and Villarrica (Chile), respectively. In all the above volcanoes, faults and fracture systems control radon degassing. Automatic and real-time measurements help us to detect major changes in volcanic activity. We present and discuss the radon time series associated with the last effusive eruption at Stromboli. Spectral analyses reveal diurnal and semi-diurnal cycles being probably modulated by atmospheric variations. Multiple linear regression (MLR) analyses have been performed by filtering the radon signals from the effects of local environmental parameters. The residuals do not show particular variations or precursory peaks as the gases have been released from this open-conduit volcano before the onset of the effusive phase (7 August 2014). It is finally emphasized that radon is not the sole precursor, and we should also rely on other geochemical and geophysical parameters. In this perspective, we propose a methodological procedure that can contribute to improving volcano surveillance in an attempt to mitigate volcanic risk.

Abstract During the period 28 February 2000–31 December 2013, the MODVOLC system (http://modis.higp.hawaii.edu) autonomously analysed almost 9 trillion (i.e. 9×10 12) pixels contained within almost 3 million MODIS images, searching for evidence of high-temperature thermal signatures associated with volcanic eruptions. Thermal unrest, mainly associated with active lava, be it in the form of flows, domes, lakes or confined to vents, was detected at 93 volcanoes during this period of time. The first part of this paper describes the physical basis and operational implementation of the MODVOLC algorithm. The second part presents data to detail the nature of the thermal emission from these 93 volcanoes over the past 14 years.