EGU22-9207, updated on 09 Jan 2023
https://doi.org/10.5194/egusphere-egu22-9207
EGU General Assembly 2022
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Volume, effusion rate, and lava transport during the 2021 Fagradalsfjall eruption: Results from near real-time photogrammetric monitoring

Gro Pedersen1, Joaquin M. C. Belart2,3, Birgir Vilhelm Óskarsson4, Magnús Tumi Guðmundsson1, Nils Gies4,5, Thórdís Högnadóttir1, Ásta Rut Hjartardóttir1, Virginie Pinel6, Etienne Berthier7, Tobias Dürig1, Hannah Iona Reynolds1, Christpher W. Hamilton1,8, Guðmundur Valsson3, Páll Einarsson1, Daniel Ben-Yehoshua9, Andri Gunnarsson10, and Björn Oddsson2
Gro Pedersen et al.
  • 1Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Sturlugata 7, 102 Reykjavík, Iceland (gro@hi.is)
  • 2Institute of Earth Sciences, University of Iceland, Sturlugata 7, 102 Reykjavík, Iceland
  • 3National Land Survey of Iceland, Stillholt 16–18, 300 Akranes
  • 4Icelandic Institute of Natural History, Urriðaholtsstræti 6–8, 210 Garðabær, Iceland
  • 5Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, 3012 Bern, Switzerland
  • 6Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, Univ. Gustave Eiff el, ISTerre, 38000 Grenoble, France
  • 7LEGOS CNRS, University of Toulouse, 31400, Toulouse, France
  • 8The University of Arizona, 1629 E University Blvd Tucson, AZ 85721-0092, USA
  • 9Faculty of Civil and Environmental Engineering, University of Iceland, Dunhagi 5, 107 Reykjavík, Iceland
  • 10The National Power Company of Iceland (Landsvirkjun), Háaleitisbraut 68, 103 Reykjavík, Iceland

The basaltic effusive eruption at Mt. Fagradalsfjall began on March 19, 2021, ending a 781-year hiatus on Reykjanes Peninsula, Iceland. At the time of writing (January 7, 2022), no eruptive activity has been observed since September 18, 2021. To monitor key eruption parameters (i.e., effusion rate and volume), near-real time photogrammetric monitoring was performed using a combination of satellite and airborne stereo images.

By late September 2021, 32 near real-time photogrammetric surveys were completed, usually processed within 3–6 hours. The results are a significant achievement in full-scale monitoring of a lava flow-field providing temporal data sets of lava volume, thickness, and effusion rate. This enabled rapid assessment of eruption evolution and hazards to populated areas, important infrastructure, and tourist centers.

The lava pathways and lava advancement were very complex and changeable as the lava filled and spilled from one valley into another and short-term prediction of the timing of overflow from one valley to another proved challenging. Analysis of thickness maps and thickness change maps show that the lava transport into different valleys varied up to 10 m3/s between surveys as lava transport rapidly switched between one valley to another.

By late September 2021, the mean lava thickness exceeded 30 m, covered 4.8 km2 and has a bulk volume of 150 ± 3 × 106 m3. Around the vent the thickness is up to 122 m. The March–September mean effusion rate is 9.5 ± 0.2 m3/s, ranging between 1–8 m3/s in March–April and increasing to 9–13 m3/s in May–September. This is uncommon for recent Icelandic eruptions, where the highest discharge usually occurs in the opening phase. This behavior may have been due to widening of the conduit by thermo-mechanical erosion with time, and not controlled by magma chamber pressure as is most common in the volcanic zones of Iceland.

How to cite: Pedersen, G., Belart, J. M. C., Óskarsson, B. V., Guðmundsson, M. T., Gies, N., Högnadóttir, T., Hjartardóttir, Á. R., Pinel, V., Berthier, E., Dürig, T., Reynolds, H. I., Hamilton, C. W., Valsson, G., Einarsson, P., Ben-Yehoshua, D., Gunnarsson, A., and Oddsson, B.: Volume, effusion rate, and lava transport during the 2021 Fagradalsfjall eruption: Results from near real-time photogrammetric monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9207, https://doi.org/10.5194/egusphere-egu22-9207, 2022.