Askja will rise again
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Askja will rise again

Written by Erik Sturkell

The results from the measurements of the Askja volcano in late July showed continuous declining subsidence. I concluded this is it, the subsidence has levelled out with the center subsiding with less than 1 cm per year. However, volcanoes can always surprise you and in early August an inflation event started and is still progressing. For two months, the surface in the southwestern part of the large Askja caldera has risen with about 10 cm!

Gabrielle and I had since long planned to go to Iceland 19-26 September to attend the Masters Day of Natural Sciences at the University of Iceland on 24 September, where our student Sigga would have her public Masters’ presentation. While Gabrielle stayed in Reykjavík and took part in the Masters Day, I had to rapidly change plans. Freysteinn arranged a field trip to Askja leaving Reykjavík early in the morning of the 20th with Elske (from the Netherlands), Josefa (PhD student from University of Leeds) and I. The four of us joined up with Sveinbjörn and Siqi at the Dreki hut in the highlands close to Askja on Monday night. They had left Reykjavík a few days before us to do additional GPS measurements and enjoyed some days with good weather. The team consisted of six persons and the hut in Dyngja was too small to host us all, so we stayed in the travel association hut in Dreki. This hut can accomoodate 42 persons, so we had it very spacious. Tuesday morning the first snow had fallen and continued with strong winds. The wind was too strong for levelling, but it was possible to do micro-gravity measurements (Fig. 1 and featured photo at the top with Freysteinn holding the umbrella to keep the gravimeter dry). The wind grew stronger during the day and at night it was a full storm. In the evening we invited all the people working in Dreki (the two rangers and two police officers) for a barbeque. Due to the storm, we made the lamb meat in the oven. Wednesday morning the wind was still too strong for levelling. Sveinbjörn, Siqi and I went to retrieve two GPS stations in the caldera and Freysteinn, Elske and Josefa performed gravity measurements all day. After lunch, Sveinbjörn, Siqi and I deployed the GPS station at Batshraun (Fig. 2). On the third day Tom and Conner from Cambridge University arrived to Askja on a seismological mission. They were to deploy and resurrect some seismic stations in and outside the caldera. On Thursday the weather was predicted to be good up to noon, so we got up at 6AM and started levelling at 7:15AM (Fig. 3). During the day it started to snow again but it was possible to continue until 3PM. By then we only had eight benchmarks left out of 35 to level. Sveinbjörn, Elske and Josefa went to the south side of the caldera to do gravity and to retrieve GPS stations. In the afternoon the snowfall intensified and the next day all was covered with 20+ centimeters of snow. It was difficult to find the road. Freysteinn and Elske left early and had some problems to find the road all the way down to Herðubreiðarlindir. Sveinbjörn and Siqi went through the snow and picked up the GPS instrument at Batshraun. Josefa and I located the remaining benchmarks in the snow, but some digging was required. Sveinbjörn and Siqi returned, and we finished the levelling line in deep snow (Fig. 4). The result from the levelling showed a completely different deformation pattern compared to the previous 38 years. The slow decay of subsidence in the center of the caldera has changed to uplift. Now magma is flowing in under the caldera floor. The location of the inflation takes place at a different location compared to the deflation center. Friday evening we drove down to Rekjahlid and the next day to Reykjavík. Thanks to, Elske, Freysteinn, Josefa, Siqi and Sveinbjörn for a fantastic fieldwork!

And congrats to Sigga and the other students for completing their Masters’ projects! All the best for the future.

Photo: Erik Sturkell. Elske and Siqi with the gravimeter at the base station DYNG.
Photo: Erik Sturkell. Figure 2. Sveinbjörn and Siqi with the GPS at Batshraun. 
Photo: Erik Sturkell. Freysteinn photographing the levelling instrument located between benchmarks 405A and 406.
Photo: Erik Sturkell. Josefa to the right and Siqi and Sveinbjörn with the rods.