Report on Fagradalsfjall (Iceland) — 28 June-4 July 2023
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 28 June-4 July 2023
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2023. Report on Fagradalsfjall (Iceland) (Sennert, S, ed.). Weekly Volcanic Activity Report, 28 June-4 July 2023. Smithsonian Institution and US Geological Survey.
63.895°N, 22.258°W; summit elev. 250 m
All times are local (unless otherwise noted)
Icelandic Meteorological Office (IMO) reported that inflation began in April in the western Reykjanes Peninsula, reaching a total of 3 cm, with rates up to about 1 cm per month. Data possibly indicated accumulating magma at 15 km depth beneath Fagradalsfjall. In June more than 1,000 earthquakes were recorded with most of them located beneath Reykjanestá, NE of Fagradalsfjall and SW of Kleifarvatn.
Seismicity intensified during 3-4 July. An earthquake swarm began at 1400 on 4 July and more than 1,600 earthquakes were detected beneath Fagradalsfjall, in the vicinity of the July 2022 dike intrusion, by mid-morning on 5 July. The earthquake locations became shallower within the first few hours of the swarm and by 5 July were at depths of 2-3 km. Seven of the earthquakes were above M 4, with the largest being M 4.6 recorded at 0821 on 5 July. At 1055 on 5 July IMO raised the Aviation Color Code to Orange (the third level on a four-color scale).
Geological Summary. Although the Fagradalsfjall fissure swarm has previously been considered a split or secondary swarm of the Krýsuvík–Trölladyngja volcanic system, as of September 2022 Icelandic volcanologists managing the Catalogue of Icelandic Volcanoes made the decision to identify it as a distinct separate system. The recent eruptions and related reports have been reassigned here, and other content will be prepared and adjusted as appropriate.