Volcanoes in Iceland – August 2025
Text and photos by Erik Sturkell
I arrived in Iceland on the 30th of July around two weeks after the start of the 16th of July volcanic eruption on Reykjanes. This eruption fissure followed the Sundhnukar crater row, and the lava flow didn’t threaten anything important, but the SO2 gas caused problems. For a few days in the beginning of the eruption both SO2 and SO4 (sulphuric acid) spread in Iceland particular in the Reykjavik area. The eruption slowed down and terminated on the 5th of August. On the same day, I travelled north to arrive in Rekjahild in the evening. The goal was to continue to Askja the next day, but before the departure to Askja I got a fantastic sweater knitted by Dísa (figure 1). My old sweater was beyond repair even by the most skilful!
This year the group consisted of several persons. Sveinbjörn and Fjóla got to Askja on Tuesday (5th of August) and started to deploy GPS stations in the southern part. The gravity survey that was planned to start on Friday started in the south, so the GPS stations were taken down freeing the sites for gravity. They continued to deploy GPS stations on the following days. Michelle, Ásta Rut, Eve (student from Genève) and I left Reykjavík in two cars on Tuesday morning and stopped in Akureyri for supply. A moment of panic struck as the centrally located alcohol shop was closed. The text on the note at the door informed that the shop had moved to the edge of the town, and this was the only shop in Akureyri. We found the shop and met the second car. We did all the shopping and continued to Rekjahild. The following day we drove to Askja and started with the levelling of the line. The first day went well and we completed a third of the line. The next morning (Thursday) it was mist and rain, so we waited until lunch when a gap in the rain opened. We went out and could measure some distance along the line until the rain came in again. Freysteinn, Elske and Elske’s daughter arrived from Akureyri on Thursday as there is a weekly fight from Amsterdam to Akureyri that came in that day. On Friday, Sveinbjörn, Fjóla, Freysteinn, Elske and Elske’s daughter went south to start with the gravity. Sveinbjörn and Fjóla took in the GPS instruments that had occupying several gravity points. To make anything out of gravity measurements the heights must be known. The measurements need to be corrected for the elevation to determine the mass as the height differences totally dominate the data. On Friday we completed the long levelling line, and the calculated numbers shows continued inflation. The yearly inflation is now the half of the initial inflation during the first two years (starting in August 2021). Elske continued with gravity in the middle of the caldera and Sveinbjörn and Fjóla deployed four GPS instruments on the northern “road” (Vikrafellsleid) and in the valley to the west (Dyngjufjalladalur). In the evening, we held a barbeque for our group and the group from the university of Genève, a total of fourteen people (Figures 2 and 3). On Saturday Sveinbjörn left for Reykjavík so he could get one day off before he took on the Cambridge seismic group. Àsta Rut and I waited a few hours for the weather to improve and then we went to the short levelling line at Bathshraun. It was occupied by Elske and Fjóla doing gravity, so we went down to the lake to measure the lake level (Figure 4). We also measured one of the sites of a benchmark from the old and destroyed tilt station which was now only a hole. In 2024 a circular hole in the rock was found and it is assumed that one of the benchmarks was in this hole. The benchmark was swept away but the hole remains (it took ten years to find it!). We guess this hole hosted the 9031benchmark. The lake level was measured from benchmark 9033. The calculation to combine the pre and post landslide is preliminary and is under the assumption we have found the location of the 9031-benchmark. The water level normally shows a ± 0.5 m variation since 2009, except for the measurement in August 2014. This water level measurement was made on the 9th of August about three weeks after the landslide. A possible explanation of the high water level 2014 is that plenty of the cracks in the lake bottom got plugged by sediment and this recovered to ”normal” the next year. After the measurements of the lake level, we returned to the short levelling line. The gravity measurements were almost done so we started in the far end. With the levelling done we left the tripod on the GPS site for Freysteinn. We met him and Michelle (coming from two directions) at Víti (Figure 5). Freysteinn was moving a GPS from the centre of the caldera to Batshraun and Michelle helped to carry all the equipment (GPS and levelling) to the car park at Vikraborgir (Figure 6). As Sveinnbjörn left I moved down to Dreki. It is boring to be alone in the little hut in the mountain. On Sunday Michelle took her research boat on the Víti crater lake and in the afternoon Ásta Rut and I took two of the Genève students to the tilt station Nautahnutur. The next day Michelle and Ásta Rut left to deploy GPS instruments in Vonaskard. I had some time to visit and look for a benchmark in Batshraun (Figure 7). It was one of Eysteinn’s lake level benchmarks, but as expected the benchmark was lost in the tsunami that followed the landslide in 2014 (Figure 8). On Tuesday (12th of August) Freysteinn, Fjóla and I took the grand circle around the Dyngjufjall (Askja) volcano to retrieve the GPS stations deployed by Sveinbjörn and Fjóla on Friday (8th of August) and to perform tilt measurements (Figures 9 and 10) at three sites (Svartadyngja, Hrútur and Lokatindur). The complete circle with measurements took about eight hours. I left Dreki 4:30 PM for Reykjahlid with the student Eve (one of the Genève students) left her in the house Helluhraun. I proceeded to visit Helgi and Júlia (figure 11) and stayed over-night. The next day I was bound to Reykjavík, but I took the road over Sprengisandur. Both for variation and to meet Michelle and Ásta Rut at Hrauneyjar. By exceptional good timing (or luck) we met at the intersection Sprengisandsleid and the road from Hágöngulón at Hnausalda. We had a pit stop at Hrauneyjar and ate a Hamburger and continued to Reykjavík.On the last day the weather forecast was good and Dori, Sonja, Greta and I went to the tilt station Næfurholt next to the volcano Hekla. This site provides information of the magma inflow under Hekla. It is a 474 meters long levelling line in a “L” shaped outline. We were visited by RUV (the Icelandic TV) and the levelling made the evening news, that Hekla is still inflating. The tilt signal shows the highest values since the measurements started in 1970 indicating new magma under the volcano.
