volcano in iceland

By Joschenbacher - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=35599563

On 1 September, the fissure in Holuhraun erupted continuously along its 600–800 m central section. The lava stretched over 4 square kilometres with an estimated volume of 20-30 million cubic metres, with a 5-10 million cubic metres increase over the previous 19 hours, the average output was about 100 cubic metres per second. A white plume rose from the eruption reaching 15,000 feet and extending 60 km NNE; no ash but high levels of sulphur dioxide were recorded.[1] In the next days, eruptions continued with the lava covering 12 square kilometres on 5 September. Reduced seismic activity continued along similar lines with activity near the tip of the dyke and larger earthquakes in the caldera. At 07:00 on 5 September two new smaller eruptions appeared in a graben to the south of the ongoing eruption about 2 km from Dyngjujökull glacier. The cauldron at Dyngjujökull appeared to have grown. Low frequency tremors continued to be detected and substantial emission of sulphur dioxide from the eruptions continued.[1] On 6 September, radar measurements of the glacier surface within the caldera showed 15 metres of subsidence, a volume change of 0.25 square kilometres. This was the largest observed subsidence in Iceland since records began in the middle of the last century. A wide shallow depression was also observed at the Dyngjujökull glacier 10 km from the ice margin, another depression 6 km from the margin deepened to 35 metres. These were likely caused by small and short sub-glacial eruptions. The fissure eruptions continued, producing 100–200 m3/s of lava which covered about 16 km2 by 7 September. Lava had now reached the western part of the Jökulsá á Fjöllum river. Follow-up measurements on 8 September indicated that since 6 September the glacier had subsided another 2.5 to 3 metres. [6] The University of Iceland said that "The events in Bárðarbunga can only be described as a slow caldera collapse".[7] On 9 and 10 September, earthquakes continued to be recorded at Bárðarbunga caldera with a M5.5 at 05:28 on the 10th in the northern part of the dyke intrusion, and also at Herðubreiðatögl. Lava was flowing into the Jökulsá á Fjöllum river, but there was no explosive reaction, only steaming. Continued sulphur dioxide emissions at the eruption sites prompted concerns about air quality in urban areas in eastern Iceland. According to GPS measurements, most of the magma flowing into the dyke was being erupted without further crustal deformation. Forecast scenarios now included references to possible further subsidence in the caldera prompting eruptions beneath the Dyngjujökull glacier. In the following days, the eruption in Holuhraun continued at a similar rate, accompanied by ongoing earthquakes. The caldera continued to subside with regular M5 earthquakes each day. Regions experiencing reduced air quality changed depending on wind direction. In the previous two days GPS monitoring had detected unusual crustal movements which may have been indicative of a change in the movement of magma under the volcano. In the month since earthquakes began at Bárðarbunga, 25,000 earthquakes had been recorded, compared to 10,000-15,000 earthquakes recorded throughout Iceland in an average year. By 21 September, subsidence in the caldera, as measured at the newly mounted GPS station, was approximately 40 cm per day and appeared to coincide with earthquake activity.[8] Lava flow and gas emissions at the eruption site in Holuhraun continued at the same strength. The lava field now extended to 37 square kilometres, with an estimated 0.4-0.5 cubic km of erupted lava.

By Milan Nykodym from Kutna Hora, Czech Republic - Bárðarbunga IV - Holuhraun, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=36544806

Seismic activity continued to be strong in October. The eruption continued apace, subsidence of the caldera continued at about 40 cm per day and the earthquakes continued with regular M5 tremors around the caldera rim and smaller tremors at the eruption site. Larger volumes of sulphur dioxide were emitted. A crater named Baugur and a new lava flow to the east formed at the eruption site in Holuhraun. Geothermal heat was on the increase and the depression in the caldera was 40 metres, subsidence continued at a similar rate to previous weeks. A cauldron in the south-east corner of Bárðarbunga deepened 25 metres in one month and was considered by scientists at the site to be linked to the depression in the caldera. Seismic activity continued in the dyke although at a reduced rate. GPS measurements around the area of activity showed minor changes. Air quality continued to be affected by the eruption. NOVEMBER Volcanic activity remained intense although there were some signs of decrease. Earthquakes continued at the dyke although there were less in number, M5+ earthquakes continued at the caldera, the subsidence of the caldera continued had reduced down from 80 cm a day at the start of the unrest to 25 cm per day, which now reached 50 metres in total. The lava field reached 76 km in area and an estimated 1 cubic kilometre volume of lava, this makes it the biggest eruption in Iceland since Laki in 1783 and the third largest lava field on Earth over this period. The lava output reduced from 200 metres per second in September to 100 m/s in November. Significant sulphur dioxide gas pollution continued to occur. The forecast was for significant activity to continue over the next few months.