Title: 2021 and 2022 Eruptions and Dike Intrusions at Mt. Fagradalsfjall, Iceland: Improving understanding of dike intrusion and eruption precursors.
Abstract: The magma plumbing system for the 2021 Fagradalsfjall eruption is revealed by complementary information derived from studies of ground deformation and seismicity versus information from geochemistry. A storage zone for magma was near the crust-mantle boundary at about 15 km depth. A narrow magma channel opened up from there and into the brittle part of the crust, where a a pre-eruptive dike formed at Fagradalsfjall with a volume of approximately 34 million cubic meters. A second intrusive period at Mt. Fagradalsfjall in December 2021 ended without an eruption (intrusive dike volume of about 8.5 million cubic meters). A third period began on 30 July 2022 (intrusive volume of about 10 million cubic meters in initial two days), with onset of an eruption on 3 August following some decline in seismicity. While a number of eruptions have well documented escalating rates of precursory activity prior to eruption, this was not observed prior to the 2021 Fagradalsfjall eruption in Iceland, suggesting a release of tectonic stress followed by a decline in deformation and seismicity rate may be a characteristic precursory activity for a certain class of eruptions. This poses challenges for forecasting volcanic activity. The difference in behaviour may to some extent relate to tectonic setting of volcanoes and the role of release of stored crustal stresses in an unrest phase preceding an eruption.
References:
https://www.nature.com/articles/s41467-020-16054-6
https://www.nature.com/articles/s41586-022-04981-x
https://www.nature.com/articles/s41586-022-05083-4
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