Slope instability and permafrost variations at Askja caldera (Iceland) investigated over 50 years with multi-sensor aerial and satellite data

• Main Authors: Shevchenko, A., Walter, T., Guðmundsson, M., Marzban, P., Belart, J., Stefanova Vassileva, M., Motagh, M., Richter, N., Kakar, N.
• Format: Conference Object
• Language: English
• Published: 2023
• Subjects: Askja; Pleiades; Iceland; permafrost; Thermokarst
• Online Access: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5017774

The morphology of Askja caldera walls demonstrates features related to slope instability and permafrost variations that can be linked to each other. However, the causal link between mass wasting and cryosphere in active volcanic environments is poorly understood. Factors of permafrost degradation and associated slope instability at Askja may involve volcanic heat flow and atmospheric temperature increase. To investigate long-term morphological changes related to slope processes and permafrost activity, we performed photogrammetric processing and comparative analysis of archive aerial, recent Pleiades satellite, and drone data. We extracted DEMs and orthophotographs covering the period of 1970-2022 and revealed evidence of slope instability, previous mass wasting occurring on different scales, and permafrost degradation. The high-resolution multitemporal data allowed recognition of such surface features as emerging tensile cracks and multiple thermokarst sinkholes. Our photogrammetric dataset was complemented with SAR and infrared data processing, and historical ground-based photographs analysis. Our results show that landslides are common at Askja caldera, and considering the identified morphological features, a new mass wasting event can occur at any time. We outline unstable areas at the caldera walls and discuss the relevance of permafrost and instability that may have contributed to the Askja 2014 rockslide avalanche. We suggest that slope instability at Askja poses significant hazards and requires constant remote sensing and on-site monitoring.