An earthquake swarm started near the Reykjanes and Eldey volcanic systems on 17th April 2022. A volcanologist was reported by the Icelandic media to have said that there is a 50% chance of another eruption on the Peninsula by the end of this year. If the eruption occurs offshore, the resulting ash may reach Reykjavik and beyond. Another possibility is that Fagradalsjall may erupt again.
So we decided to plot the earthquakes on the Reykjanes Peninsula from 1st January 1995 to 26th April 2022 for the area 63.6°N, 23.5°W to 64.2°N, 21.0°W by month. The results are interesting.
Intense earthquake activity starts early 1995 in the east of the region to the south east of Hengill near the Hrómundartindur volcanic system, which has not erupted since the early Holocene. Activity migrates slowly westward to Geirfuglasker via Krýsuvík, Fagradalsfjall, Reykjanes, and the intensity of activity near Hrómundartindur lessens. The volcano-tectonic episode which resulted in the eruption at Geldingadalir started in month 300, the eruption, itself, started in month 315.
We have discussed the Hengill, Brennisteinfjöll, Krýsuvík and Reykjanes volcanic systems in an earlier post (Recent Seismic Activity on the Reykjanes Peninsula, 14th May 2020) The Hrómundartindur system is about 25 km long, comprising a fissure swarm and a 500m high central volcano. The system lies at the junction of the Western Volcanic Zone and the South Iceland Seismic Zone. Its lavas range from picrite to basaltic andesite. There is an active geothermal field in the system. The Eldey volcanic system is a 40km long fissure system on the Mid Atlantic Ridge, here, the Reykjanes Ridge. There is no central volcano. It is mostly submarine; the island Eldey and the skerries, Eldeyjardrangur, Geirfugladrangur and Geirfuglasker, are the only subaerial features of the system. Six small submarine/explosive Basaltic eruptions have occurred in the last 1,100 years, the last eruption occurring in 1926 CE.
We would not like to predict where the next eruption will be based on the above earthquake plots alone, other than to say it could be anywhere between Hrómundartindur and Geirfuglasker. Our non-expert interpretation of the above plots is that magma is ascending between Krýsuvík and Reykjanes. The seismic activity to the east and west of that area is caused by resulting stress on the crust; whether there is enough activity to provide an additional path for magma remains to be seen. Time will tell where and when magma makes it to the surface again.
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Reykjavik Grapevine: From Iceland — RVK Newscast 179: Underwater Volcano On The Cards (grapevine.is)
Kristján Sæmundsson (Iceland GeoSurvey) (2019 November 15). Hrómundartindur. In: Oladottir, B., Larsen, G. & Guðmundsson, M. T. Catalogue of Icelandic Volcanoes. IMO, UI and CPD-NCIP. Retrieved from http://icelandicvolcanoes.is/?volcano=HRO
Guðrún Larsen (Institute of Earth Sciences – Nordvulk, University of Iceland) (2019 November 15). Eldey. In: Oladottir, B., Larsen, G. & Guðmundsson, M. T. Catalogue of Icelandic Volcanoes. IMO, UI and CPD-NCIP. Retrieved from http://icelandicvolcanoes.is/?volcano=ELD
Raw earthquake data: Icelandic Meteorological Office