An interpretative view of open-vent volcanoes

Abstract

Open-vent volcanoes are special systems where the dynamics of sustained magmatic processes can be thoroughly investigated and where new monitoring tools can be tested and applied. However, various aspects remain puzzling at open-vent volcanoes for which forecasting their behaviour can be an important challenge. Recent papers highlight the very rapid improvements in spaceborn instruments, data acquisition techniques, data treatment and modelling over the last decade, and illustrate the fundamental contribution of long time-series data, either discontinuous or continuous, and the development of multi-parameter studies.Here we provide an interpretative overview of the main characteristics of open-vent volcanoes on the basis of selected examples chosen to be representative of the diversity of their magma composition, their eruptive activity and their geodynamic context. We choose typical open-vent volcanoes (Stromboli, Yasur and Erebus), some of them hosting a lava lake (Erta 'Ale, Nyiragongo, Villarrica, Ambrym and Masaya), to those with vigourous activity, which are associated to a longlasting eruption (Arenal, Fuego, Popocatépetl, Santiaguito). We briefly review their surface activity and report the values of SO 2 flux and the derived magma supply rate with emphasis on the key results found on their behaviour. We show the key role of the magma viscosity and its implication on the degassing. We present the current models used to explain how an open-vent volcano could be maintained, such as by the simultaneous rise and fall of a degassing and degassed magma (bidirectional flow models) and the few thermal models at lava lakes and in the conduit. Finally we discuss the sulphur evolution for three nearby volcanoes at the triple junction in Central America (Pacaya, Fuego, Santiaguito).

Lava dome cycles reveal rise and fall of magma column at Popocatépetl volcano

“…The combined observations suggest that: (1) the short-term dome construction-subsidence cycles resemble gas-driven ups and downs of the uppermost magma column, where retention and escape of exsolved gas are responsible for magma extrusion and withdrawal from the conduit, (2) the long-term progressive inner-crater deepening and the concomitant decrease in heat/gas fluxes could reflect the progressive depressurization of the magma conduit and reservoir due to progressive gas depletion, (3) the excess degassing and excess thermal radiation of the system suggests that unerupted magma is degassing and cooling at shallow levels below the crater floor. These observations echo those reported at other low-viscosity lava domes 12 , 21 , 24 , and remind magmatic processes operating in the upper magma column of more basaltic open-systems 41 . Such multiparametric analyses could in the future be applied to other open-systems, and help constrain the overarching characteristics of open-vent volcanic activity and associated hazards 41 , 42 .…”

“…The results are consistent with observations at other low-viscosity lava dome volcanoes, and point to unexpected similarities with magmatic processes operating in the upper magma column of more basaltic open-systems. This study opens new perspectives to constrain the overarching characteristics of open-vent volcanic activity 41 , 42 , and paves the way to improved multidisciplinary satellite volcano monitoring 43 and hazard assessment.…”

CO2 Flushing Triggers Paroxysmal Eruptions at Open Conduit Basaltic Volcanoes

“…Paroxysmal explosions are sudden and violent blasts that occasionally interrupt the mild explosive activity of persistently active, mafic open‐vent volcanoes worldwide, such as Stromboli (Andronico et al., 2021; Edmonds et al., 2022; Papale, 2018; Rosi et al., 2000; Vergniolle & Métrich, 2022) and Etna (Corsaro & Miraglia, 2022) in Italy; Villarrica in Chile (Aiuppa et al., 2017). Forecasting these events, and understanding their driving mechanisms, have traditionally been hindered by the apparent lack of precursory changes in surface activity, which point to a deep trigger (Aiuppa et al., 2010; Allard, 2010; Harris & Ripepe, 2007).…”

Volcano Opto‐Acoustics: Mapping the Infrasound Wavefield at Yasur Volcano (Vanuatu)

“…It can be present between explosions and/or when explosions are absent, and may be excited by roiling of the magma surface and/or by vigorous degassing (e.g., Ripepe et al., 2010; Goto & Johnson, 2011). At Yasur, both passive degassing and Strombolian‐style explosive degassing are common (e.g., Vergniolle & Metrich, 2022), and their contributions to total gas output has been measured as comparable (i.e., ∼60% passive vs. ∼40% explosive (Ilanko et al., 2020)).…”