Multidisciplinary constraints of hydrothermal explosions based on the 2013 Gengissig lake events, Kverkfjöll volcano, Iceland

• Published in: Earth and Planetary Science Letters
• Main Authors: Montanaro, Cristian, Scheu, Bettina, Gudmundsson, Magnus Tumi, Vogfjörd, Kristín, Reynolds, Hannah Iona, Dürig, Tobias, Strehlow, Karen, Rott, Stefanie, Reuschlé, Thierry, Dingwell, Donald Bruce
• Other Authors: Ludwig Maximilian University Munich = Ludwig Maximilians Universität München (LMU), University of Iceland Reykjavik, Icelandic Meteorological Office (IMO), University of Bristol Bristol, Géophysique expérimentale (IPGS) (IPGS-GE), Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Ecole et Observatoire des sciences de la terre (EOST), Institut national des sciences de l'Univers (INSU - CNRS)-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), CM, BS, MTG, HIR, and KS acknowledge the support of the European Commission (FP7-MC-ITN, grant number 289976: NEMOH). KSV, MTG and TD acknowledge support from EC FP7 grant number 308377, FUTUREVOLC. BS and DBD acknowledge support from the EC FP7 under grant agreement No. 282759 (VUELCO). CM, BS and DBD acknowledge support from EC FP7 grant agreement No. 308665 (MED-SUV). DBD acknowledges the support of ERC Advanced Grant No. 247076 (EVOKES).
• Format: Article in Journal/Newspaper
• Language: English
• Published: CCSD 2016
• Subjects: hydrothermal explosions; lake drainage; multidisciplinary; deposits volume; energy partitioning; [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; Dammed Lake; Kverkfjöll; Vatnajökull; Iceland
• Online Access: https://hal.science/hal-02336311; https://hal.science/hal-02336311v1/document; https://hal.science/hal-02336311v1/file/1_s2.0_S0012821X15007475_main.pdf; https://doi.org/10.1016/j.epsl.2015.11.043

International audience Hydrothermal explosions frequently occur in geothermal areas showing various mechanisms and energies of explosivity. Their deposits, though generally hardly recognised or badly preserved, provide important insights to quantify the dynamics and energy of these poorly understood explosive events. Furthermore the host rock lithology of the geothermal system adds a control on the efficiency in the energy release during an explosion. We present results from a detailed study of recent hydrothermal explosion deposits within an active geothermal area at Kverkfjöll, a central volcano at the northern edge of Vatnajökull. On August 15th 2013, a small jökulhlaup occurred when the Gengissig ice-dammed lake drained at Kverkfjöll. The lake level dropped by approximately 30 m, decreasing pressure on the lake bed and triggering several hydrothermal explosions on the 16th. Here, a multidisciplinary approach combining detailed field work, laboratory studies, and models of the energetics of explosions with information on duration and amplitudes of seismic signals, has been used to analyse the mechanisms and characteristics of these hydrothermal explosions. Field and laboratory studies were also carried out to help constrain the sedimentary sequence involved in the event. The explosions lasted for 40–50 s and involved the surficial part of an unconsolidated and hydrothermally altered glacio-lacustrine deposit composed of pyroclasts, lavas, scoriaceous fragments, and fine-grained welded or loosely consolidated aggregates, interbedded with clay-rich levels. Several small fans of ejecta were formed, reaching a distance of 1 km north of the lake and covering an area of approximately 0.3 km2, with a maximum thickness of 40 cm at the crater walls. The material (volume of approximately 104 m3) has been ejected by the expanding boiling fluid, generated by a pressure failure affecting the surficial geothermal reservoir. The maximum thermal, craterisation and ejection energies, calculated for the explosion areas, are ...