TY - JOUR

T1 - Hydrothermally altered deposits of 2014 Askja landslide, Iceland, identified by remote sensing imaging

AU - Marzban, Pouria

AU - Bredemeyer, Stefan

AU - Walter, Thomas R.

AU - Kästner, Friederike

AU - Müller, Daniel

AU - Chabrillat, Sabine

N1 - Funding Information: We are grateful for the kind help of Tanja Witt, Anne Schöpa, Bastian Steinke and Constantin Hildebrand during our fieldwork, and Heiko Woith and Magnus Tumi Gudmundsson for various discussions on Askja. Our acknowledgements to Planet Labs Education and Research Standard Program for providing us the PlanetScope/RapidEye imagery. We appreciate discussion and support by Magdalena Stefanova Vassileva and Mahdi Motagh from the GFZ Section 1.4 (Remote Sensing and Geoinformatics). We also appreciate the support by Ferdafelag Akureyrar for allowing hospitality and battery recharge at Dreki, and the Vatnajökull National Park for research and the exceptional drone permit. Funding Information: The Funding was partially provided by VOLCAPSE, a research project funded by the European Research Council under the European Union’s H2020 Programme/ERC consolidator grant ERC-CoG 646858. Travels were financially supported through GFZ expedition grants.

PY - 2023/3/9

Y1 - 2023/3/9

N2 - Volcanic flanks subject to hydrothermal alteration become mechanically weak and gravitationally unstable, which may collapse and develop far-reaching landslides. The dynamics and trajectories of volcanic landslides are hardly preserved and challenging to determine, which is due to the steep slopes and the inherent instability. Here we analyze the proximal deposits of the 21 July 2014, landslide at Askja (Iceland), by combining high-resolution imagery from satellites and Unoccupied Aircraft Systems. We performed a Principal Component Analysis in combination with supervised classification to identify different material classes and altered rocks. We trained a maximum-likelihood classifier and were able to distinguish 7 different material classes and compare these to ground-based hyperspectral measurements that we conducted on different rock types found in the field. Results underline that the Northern part of the landslide source region is a hydrothermally altered material class, which bifurcates halfway downslope and then extends to the lake. We find that a large portion of this material is originating from a lava body at the landslide headwall, which is the persistent site of intense hydrothermal activity. By comparing the classification result to in-situ hyperspectral measurements, we were able to further identify the involved types of rocks and the degree of hydrothermal alteration. We further discuss associated effects of mechanical weakening and the relevance of the heterogeneous materials for the dynamics and processes of the landslide. As the study demonstrates the success of our approach for identification of altered and less altered materials, important implications for hazard assessment in the Askja caldera and elsewhere can be drawn.

AB - Volcanic flanks subject to hydrothermal alteration become mechanically weak and gravitationally unstable, which may collapse and develop far-reaching landslides. The dynamics and trajectories of volcanic landslides are hardly preserved and challenging to determine, which is due to the steep slopes and the inherent instability. Here we analyze the proximal deposits of the 21 July 2014, landslide at Askja (Iceland), by combining high-resolution imagery from satellites and Unoccupied Aircraft Systems. We performed a Principal Component Analysis in combination with supervised classification to identify different material classes and altered rocks. We trained a maximum-likelihood classifier and were able to distinguish 7 different material classes and compare these to ground-based hyperspectral measurements that we conducted on different rock types found in the field. Results underline that the Northern part of the landslide source region is a hydrothermally altered material class, which bifurcates halfway downslope and then extends to the lake. We find that a large portion of this material is originating from a lava body at the landslide headwall, which is the persistent site of intense hydrothermal activity. By comparing the classification result to in-situ hyperspectral measurements, we were able to further identify the involved types of rocks and the degree of hydrothermal alteration. We further discuss associated effects of mechanical weakening and the relevance of the heterogeneous materials for the dynamics and processes of the landslide. As the study demonstrates the success of our approach for identification of altered and less altered materials, important implications for hazard assessment in the Askja caldera and elsewhere can be drawn.

KW - Askja landslide

KW - classification

KW - hydrothermal alteration

KW - PCA

KW - remote sensing

KW - volcano hazards

UR - http://www.scopus.com/inward/record.url?scp=85150686371&partnerID=8YFLogxK

U2 - 10.3389/feart.2023.1083043

DO - 10.3389/feart.2023.1083043

M3 - Article

AN - SCOPUS:85150686371

VL - 11

JO - Frontiers in Earth Science

JF - Frontiers in Earth Science

SN - 2296-6463

M1 - 1083043

ER -