During 17-23 September, IMO maintained Aviation Colour Code Orange due to continued activity at Bárdarbunga’s Holuhraun eruptive fissure. Chemical analysis and geophysical modeling indicated that the source of the magma was at a depth of more than 10 km. Persistent subsidence was detected from the Bárdarbunga caldera and crustal movements signified that the volume of magma in the dyke slightly increased. On 21 September the lava field measured 37 square kilometers. Field scientists estimated that about 90% of the sulfur dioxide gas from the eruption originated at the active craters and the rest rose from the lava field. Dead birds were also found around the eruption site. A report on 22 September noted that the total volume of the erupted lava was 0.4-0.6 cubic kilometers and the flow rate was 250-350 cubic meters per second. Persistent subsidence was detected from the Bárdarbunga caldera; the volume of the depression was an estimated 0.6 cubic kilometers on 23 September.

Geological Summary. The large central volcano of Bárðarbunga lies beneath the NW part of the Vatnajökull icecap, NW of Grímsvötn volcano, and contains a subglacial 700-m-deep caldera. Related fissure systems include the Veidivötn and Trollagigar fissures, which extend about 100 km SW to near Torfajökull volcano and 50 km NE to near Askja volcano, respectively. Voluminous fissure eruptions, including one at Thjorsarhraun, which produced the largest known Holocene lava flow on Earth with a volume of more than 21 km3, have occurred throughout the Holocene into historical time from the Veidivötn fissure system. The last major eruption of Veidivötn, in 1477, also produced a large tephra deposit. The subglacial Loki-Fögrufjöll volcanic system to the SW is also part of the Bárðarbunga volcanic system and contains two subglacial ridges extending from the largely subglacial Hamarinn central volcano; the Loki ridge trends to the NE and the Fögrufjöll ridge to the SW. Jökulhlaups (glacier-outburst floods) from eruptions at Bárðarbunga potentially affect drainages in all directions.

Source: Icelandic Meteorological Office (IMO)