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Structural and temporal analysis of a caldera collapse using high-resolution drone imagery: Askja volcano, central Iceland.

Nicolas Serrano1, Nicolas Oestreicher2, Thorsteinn Saemundsson3, Elisabetta Panza1, Joël Ruch1

  • Affiliations:  1 Department of Earth Sciences, University of Geneva, Geneva, Switzerland 2  WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland. 3 Faculty of Life and Environmental Sciences, University of Iceland, Reykjavik, Iceland. 

  • Presentation type: Poster

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

  • Poster Board Number: 65

  • Programme No: 3.11.25

  • Theme 3 > Session 11

Abstract

Volcanism in Iceland is expressed by volcanic systems, constituted by fissure swarms and the related central volcanoes, often in the form of calderas. The structural interaction between regional rift faults and caldera structures plays a critical role in controlling volcano morphology, fluid circulation, and volcano flank stability. However, this interaction and the related volcano tectonic processes in time remain poorly studied. We used high-resolution digital elevation models (DEMs) and orthophotos derived from drone imagery to map and analyze ~4400 volcanic and tectonic structures along the eastern wall of the Öskjuvatn caldera. This caldera is the most recent at Askja central volcano, formed in 1875 during a Plinian eruption. The structural analysis was complemented by field observations collected in August 2023 and by 3D modeling to enhance spatial and structural interpretations. Our analysis focuses on the 1875 collapse sequence that shaped the current Öskjuvatn caldera wall, with major N130° collapse faults concentrated in the northeast that are nowadays inactive. Also, to the southeast, we mapped in detail a large landslide that occurred in 2014, displaying a general N030° fracture direction with active landslides and intense hydrothermal activity. Therefore, this cliff is characterized by concentric fracture systems that contrast with long lived rift-related faults that cross-cut the Eastern portion of the caldera wall with N030° trend. We suggest that the coalescence of these fracture sets is a critical factor in the caldera's collapse history, current morphology, and ongoing hydrothermal and gravitational activity.