Report on Fagradalsfjall (Iceland) — 11 August-17 August 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
11 August-17 August 2021
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2021. Report on Fagradalsfjall (Iceland). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 11 August-17 August 2021. Smithsonian Institution and US Geological Survey.
63.895°N, 22.258°W; summit elev. 250 m
All times are local (unless otherwise noted)
The fissure eruption in the W part of the Krýsuvík-Trölladyngja volcanic system, close to Fagradalsfjall on the Reykjanes Peninsula, continued during 11-17 August. According to the Institute of Earth Sciences photographs of the flow field captured on 8 August suggested that the lava effusion rate averaged 9.3 cubic meters per second over the previous 12 days. The area of the flow field had grown to 4.4 square kilometers, and the total volume erupted was 119 million cubic meters. New ground cracks were observed in Gónhóll, a hill S of the main crater (the fifth vent) that was a former vantage point but is now surrounded by lava, though they had likely formed sometime in the previous two weeks and may not have been caused by rising magma. A new vent that opened on 9 August was not confirmed to be separate from the nearby main vent until about a week later. The new cone quickly grew from intense spattering and by 17 August was around the same height as the main crater. Spattering from the new vent was at times ejected higher than spatter from the main vent. The Aviation Color Code remained at Orange due to the lack of ash and tephra emissions, though IMO warned of the potential for lapilli and scoria fallout within a 650 m radius of the active vent. Authorities also warned of gas emissions hazards.
Geological Summary. Although the Fagradalsfjall fissure swarm has previously been considered a split or secondary swarm of the Krýsuvík–Trölladyngja volcanic system (https://volcano.si.edu/volcano.cfm?vn=371030), as of September 2022 Icelandic volcanologists managing the Catalogue of Icelandic Volcanoes (https://icelandicvolcanoes.is/) made the decision to identify Fagradalsfjall 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 in the next few months.