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Report on Krysuvik-Trolladyngja (Iceland) — 15 September-21 September 2021


Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
15 September-21 September 2021
Managing Editor: Sally Kuhn Sennert

Please cite this report as:

Global Volcanism Program, 2021. Report on Krysuvik-Trolladyngja (Iceland). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 15 September-21 September 2021. Smithsonian Institution and US Geological Survey.

Weekly Report (15 September-21 September 2021)



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

All times are local (unless otherwise noted)

The eruption from the fifth vent in the W part of the Krýsuvík-Trölladyngja volcanic system, close to Fagradalsfjall on the Reykjanes Peninsula, continued during 15-18 September. According to a news article lava ponded for a few days in Geldingadalur, and during 14-15 September the crust ruptured and sent a larger lava flow rapidly into the S part of the valley; the flow then turned E into the Nàtthagi valley. Authorities temporarily closed the area due to the activity and the large number of tourists; the Coast Guard rescued two people whose exit route had been cut off by the flow. Lava continued to flow on this path during 16-17 September and overtook the “A” hiking trail. Later that day at around 1800 the flow rate decreased or paused, and only minor incandescence from the vent was visible.

The Institute of Earth Sciences reported that based on aerial photography acquired on 17 September the area of the flow field had grown to 4.8 square kilometers, and the total volume erupted was 151 million cubic meters. The lava-flow rate during 11-17 September averaged 16 cubic meters per second. IMO noted that 19 September marked six months since the eruption started.

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.

Sources: Icelandic Meteorological Office (IMO), Institute of Earth Sciences, Icelandic National Broadcasting Service (RUV), Icelandic National Broadcasting Service (RUV), Almannavarnadeild ríkislögreglustjóra (National Commissioner of the Icelandic Police and Department of Civil Protection and Emergency Management), Dr. Evgenia Ilyinskaya (University of Leeds)