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Crater Rims or Graben Faults? Ground-Penetrating Radar Insights into the Eldgjá Canyon Formation, Iceland

Diana Brum da Silveira1 , Thorvaldur Thordarson1, Ármann Höskuldsson2, Ingibjörg Jónsdóttir1, William M. Moreland3

  • Affiliations: 1Faculty of Earth Sciences, University of Iceland, Reykjavík, Iceland; 2Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland; 3Icelandic Met Office, Reykjavík, Iceland

  • Presentation type: Poster

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

  • Poster Board Number: 118

  • Programme No: 3.15.23

  • Theme 3 > Session 15

Abstract

Comprehensive models of volcanic deposit distribution can be built by correlating Ground-penetrating radar (GPR) data with geological and stratigraphic observations. GPR has many applications in geophysical and geological research. However, its use for studying volcanic deposits remains underdeveloped. The unique nature of volcanic materials poses challenges in interpreting radar profiles, and therefore, developing a standardised method for applying GPR methodology to volcanic materials is preferable. The Eldgjá eruption, part of Iceland's Katla volcanic system, stands out as one of the most notable explosive basaltic eruptions in historical times, occurring in 934 CE. The Eldgjá fissure is one of the largest in Iceland, located in the southern Icelandic highlands. However, the proximal vent deposits are unclear about the vents, particularly within the Eldgjá Canyon. GPR offers a potential for characterising and mapping the proximal Eldgjá eruptive units. Are the canyon walls crater rims or graben faults, as suggested by some previous researchers? To achieve this, traditional fieldwork observations and GPR surveys were conducted during the summer of 2024. The GPR successfully mapped various volcanic units in key locations such as the Eldgjá Canyon and Skælingar, ranging from proximal tephra fall to fire fountains deposits, with the latter varying from spatter and lapilli to rheomorphic lava layers. Field calibration of the GPR indicates proximal fire fountain deposits that rapidly thin 30-40m from the cliff edges within the Eldgjá Canyon. Accordingly, we propose that these cliffs are not graben faults but rather the crater rims of the Eldgjá 934 eruption.