Near-surface magma flow instability drives cyclic lava fountaining at Fagradalsfjall, Iceland.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 37935706.
- Also identified by DOI 10.1038/s41467-023-42569-9 and PMC identifier 10630439.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Lava fountains are a common manifestation of basaltic volcanism. While magma degassing plays a clear key role in their generation, the controls on their duration and intermittency are only partially understood, not least due to the challenges of measuring the most abundant gases, H<sub>2</sub>O and CO<sub>2</sub>. The 2021 Fagradalsfjall eruption in Iceland included a six-week episode of uncommonly periodic lava fountaining, featuring ~ 100-400 m high fountains lasting a few minutes followed by repose intervals of comparable duration. Exceptional conditions on 5 May 2021 permitted close-range (~300 m), highly time-resolved (every ~ 2 s) spectroscopic measurement of emitted gases during 16 fountain-repose cycles. The observed proportions of major and minor gas molecular species (including H<sub>2</sub>O, CO<sub>2</sub>, SO<sub>2</sub>, HCl, HF and CO) reveal a stage of CO<sub>2</sub> degassing in the upper crust during magma ascent, followed by further gas-liquid separation at very shallow depths (~100 m). We explain the pulsatory lava fountaining as the result of pressure cycles within a shallow magma-filled cavity. The degassing at Fagradalsfjall and our explanatory model throw light on the wide spectrum of terrestrial lava fountaining and the subsurface cavities associated with basaltic vents.