Long-term impacts of volcanic eruptions on glacier dynamics – a case study of the 2010 summit eruption of Eyjafjallajökull, Iceland

Several eruptions at glacierized volcanoes have been witnessed during the 20th and 21st centuries. However, most of the published studies of these eruptions have focused on understanding the volcanic products or the hazards generated by volcano-ice interactions. Much less attention has been put into analyzing the effects on the glaciers. During the 2010 summit eruption of Eyjafjallajökull (Iceland) three different areas of its glacier were affected in distinct ways: (i) The summit caldera by the formation of eruption vents—the main one active for almost six weeks; (ii) the southern flank by a short-lived (one day) eruption fissure; and (iii) the outlet glacier Gígjökull by (subglacial) lava propagation over more than two weeks. Lava accumulation started subglacially in the caldera and eventually became subaerial while progressing northwards, finally reaching a length of more than three km.

Here we study how the ice cap has evolved after the eruption and how individual areas have changed with time. We use elevation data obtained from Pléiades, SPOT5, LiDAR scans, and overflights to calculate elevation and volume changes over varying time periods. Aerial photographs and on-site investigations helped documenting visual changes. Lastly, we used Ground Penetrating Radar (GPR) to map the depth to the 2010 tephra layer in the accumulation area and to the volcanic bedrock.

While signs of the eruption on the southern flank have completely vanished, the areas in the caldera have not fully recovered. This is most notable in the northern part of the caldera where subglacial lava emplacement started. However, snow accumulation and thus gain in elevation in most of the impacted areas started quickly after the eruption ended. From August 2010 to August 2014 the area of the main vent showed an elevation increase of more than 80 m. A similar increase was visible on top of the lava pile towards the north. Gígjökull also started to recover, although the glacier front has been alternating between advance and retreat—similar to the pre-eruption time. Volume change and area calculations reveal that the ice cap overall is shrinking. The glacier covered an area of 72.3 km² in 2010 and decreased to 63.5 km² in 2024, with an average elevation change of -8.3 m. However, the caldera and Gígjökull do not follow this trend and showed a persistent volume increase over various time periods from 2010 to 2024, corresponding to an average elevation change of +13.4 m. A potential explanation for the fast recovery of the summit area is the positive feedback effect on the mass balance. The depressions formed by the eruption acted as traps for drifting snow in winter, resulting in a local thickening rate far exceeding the average winter accumulation. Sporadic geothermal activity has also been detected. This includes the re-emergence of a minor cauldron in October 2024 which was first observed in 2012.