Morphological changes of the south-eastern wall of Askja caldera, Iceland over the past 80 years

Abstract Calderas are subcircular depressions with near-vertical walls, which are often gravitationally unstable and prone to mass movements that sequentially widen their basins. However, the details of these erosional changes are difficult to decipher due to short observational periods. Here, we use a photogrammetric dataset of nearly 80 years to study the landslide-prone south-eastern wall of Askja caldera (Iceland). We analyzed aerial data from 1945 and 1987, stereo satellite data from 2013 and 2022, and drone images acquired in 2019, 2022, and 2023. We developed an inventory of geomorphological features and identified types of slope instability. We describe over 700 features, including circa 500 fractures, 200 sinkholes, and four major landslides. We found that morphological changes were persistent over the observation period, accumulating in a sector that collapsed in 2014. We discuss various factors of slope instability at Askja including possible volcano-permafrost interaction, and other processes that could induce mass wasting.