Report on Krysuvik-Trolladyngja (Iceland) — 28 July-3 August 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
28 July-3 August 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, 28 July-3 August 2021. Smithsonian Institution and US Geological Survey.
63.917°N, 22.067°W; summit elev. 360 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 28 July-3 August. Lava fountaining and overflows from the fifth vent occurred at intervals of 10-15 hours, with similarly long periods of no activity in between; this pattern emerged around 17 July. According to the Institute of Earth Sciences an overflight was conducted on 27 July; based on new measurements, the lava effusion rate averaged 11 cubic meters per second during 2-27 July, though the average since 17 July was likely lower. The area of the flow field had grown to 4.3 square kilometers, and the total volume erupted was 109 million cubic meters. Lava flowed into the Meradalir Valley and areas to the W and did not advance in the Geldingadalur, Nátthaga, and Sydri Meradalir (SE of the fifth vent) valleys. The flows in Meradalir thickened about 1 m per day. 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. 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.