Paraglacial exposure and collapse of glacial sediment: The 2013 landslide onto Svínafellsjökull, southeast Iceland

In the last 130 years, Icelandic glaciers have experienced significant mass loss, and numerous paraglacial slope failures have been documented in the country. One such failure occurred in late February 2013, when a large landslide fell onto the Svínafellsjökull outlet glacier in southeast Iceland. Digital elevation models and aerial imagery were used to quantify the glacial and paraglacial changes leading up to the event, reconstructing the processes that occurred during the landslide and the effects of the debris on the glacier surface. Between 1994 and 2013, glacier thinning and glacier-retreat exposed a steep lateral moraine perched on bedrock which later failed and caused the landslide. Increased pore-water pressure after an intense rainstorm and potential fluvial erosion at the toe of the source area are considered to be the primary trigger mechanisms. Morphological evidence indicates multiple phases of movement in the source area and a highly water-rich debris avalanche on Svínafellsjökull. The debris reached a runout distance of almost 4 km and affected an area of about 1.7 km². The estimated displaced volume of the slide is 5.33 ± 0.08 × 10⁶ m³, making it the largest documented landslide originating from unconsolidated material in Iceland. The glacier surface ablation beneath the debris deposits was reduced due to insulation, whereas increased glacier thinning was observed surrounding the deposits, resulting in an up to 35 m height difference between the debris-free and the debris-covered ice by 2020. This study shows that large catastrophic landslides can originate from, and result in the formation of ice-cored or frozen sediment complexes and highlights the potential risk coming from similar slopes around the world as glaciers continue to recede and the number of paraglacial landslides increases.