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Report on Krysuvik-Trolladyngja (Iceland) — 27 July-2 August 2022


Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
27 July-2 August 2022
Managing Editor: Sally Kuhn Sennert

Please cite this report as:

Global Volcanism Program, 2022. Report on Krysuvik-Trolladyngja (Iceland). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 27 July-2 August 2022. Smithsonian Institution and US Geological Survey.

Weekly Report (27 July-2 August 2022)



63.917°N, 22.067°W; summit elev. 360 m

All times are local (unless otherwise noted)

Icelandic Meteorological Office (IMO) reported that an intense earthquake swarm began around noon on 30 July within the Krýsuvík-Trölladyngja volcanic system. The earthquakes were located in an area just NE of lava field in Geldingadalir, along the dike intrusion that preceded the March-September 2021 eruption. The swarm was likely caused by a magmatic intrusion at depths of 5-7 km. Earthquakes were reportedly felt in SW Iceland, in Reykjanesbær, Grindavík, the Capital region, and as far as Borgarnes. Several earthquakes were above M 3; a larger M 4 event was recorded at 1403. IMO raised the Aviation Color Code to Yellow, based on above-background seismic levels. At around 1800 the epicenters shallowed to depths of 2-5 km. By 1527 on 31 July almost 3,000 earthquakes had been detected, with four of the events larger than an M 4. A larger M 5.4 earthquake was detected at 1748. IMO reported at 1749 on 2 August that deformation models indicated magma around 1 km below the surface. The intrusion rate was close to double that recorded prior to the 2021 eruption, though by the reporting time the intrusion and seismicity rates had slowed. IMO noted that a similar pattern of events took place prior to the last eruption and stated that the likelihood of an eruption had increased. An effusive eruption began at 1315 on 3 August in Meradalir, near the border of the previous flow field N of Fagradalsfjall. Webcam video showed lava fountains rising along a 300-m-long fissure. As a result, IMO raised the Aviation Color Code to Orange at 1536. Gas-and-steam plumes rose 500-1,000 m high, but no ash was detected.

Geological Summary. The Krýsuvík-Trölladyngja volcanic system is described by the Catalogue of Icelandic Volcanoes as an approximately 50-km-long composite fissure swarm trending about N38°E, including a 30-km-long swarm of fissures, with no central volcano. It is one of the volcanic systems arranged en-echelon along the Reykjanes Peninsula west of Kleifarvatn lake. The Fagradalsfjall and Krýsuvík fissure swarms are considered splits or secondary swarms of the Krýsuvík–Trölladyngja volcanic system. Small shield volcanoes have produced a large portion of the erupted volume within the system. Several eruptions have taken place since the settlement of Iceland, including the eruption of a large basaltic lava flow from the Ogmundargigar crater row around the 12th century. The latest eruption, identified through tephrochronology, took place during the 14th century.

Source: Icelandic Meteorological Office (IMO)