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Volcano-glacier interactions during a silicic phreatoplinian eruption at Katla volcano in the Younger Dryas

Rosie Cole1 , Magnús Tumi Gudmundsson1, Brian Jicha2, Birgir Vilhelm Óskarsson3, Catherine Gallagher1, Esther Ruth Guðmundsdóttir1, Guðrún Larsen1, James White4

  • Affiliations: 1Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland; 2WiscAr Laboratory, University of Madison-Wisconsin, Madison, USA; 3Natural Science Institute of Iceland, Garðabær, Iceland; 4Geology Department, University of Otago, Dunedin, New Zealand

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 192

  • Programme No: 3.3.23

  • Theme 3 > Session 3

Abstract

Silicic eruptions that occurred at the end of the last glaciation at Katla volcano have distributed tephra across northern Europe and the North Atlantic. The resulting tephra layers are valuable stratigraphic markers for Quaternary studies, but since the eruptions have likely all occurred through an ice cap, proximal deposits are sparsely preserved. We present detailed geological maps for two nunataks exposed in the Mýrdalsjökull glacier. The nunataks record explosive eruption of silicic tephra with synchronously emplaced rhyolite lava flows and intrusions. Based on physical characteristics of the deposits, we infer a phreatoplinian eruption involving explosions and lava effusion from multiple englacial vents around the Katla caldera. 40Ar/39Ar dating of the capping lavas determined ages of ~12 ka for both nunataks. These ages, as well as the geochemistry, of the lavas and tephras are comparable with those of the Vedde Ash, a well-known distal ash layer originating from a Katla eruption dated to 12.1 ka. We propose that the nunataks preserve the proximal deposits of this significant eruption. At the end of the last glacial period, retreat of the Icelandic Ice Sheet was rapid and coincided with increased volcanic activity. Empirical evidence to support paleoenvironmental reconstructions in south Iceland is fragmentary, however. We use the physical characteristics of the lavas on the nunataks to reconstruct the ice surface profile over Katla at the time of eruption. Further, we discuss the possible influence of deglaciation and unloading on the Katla magmatic system in facilitating this phreatoplinian eruption.