Under-ice volcanic eruption at Vatnajökull Glacier in Iceland triggers sudden flooding and strong sulphuric smell along the Skafta river

The river Skaftá in Southern Iceland is currently flooding and everything indicates the increasing level of water is linked to geothermal and volcanic activity…

Electrical conductivity in the river has increased steadily over the past two days, an indication that geothermal factors are involved.

According to the Icelandic Meteorological Office, sulphuric smells have also been reported in the vicinity of Skaftá and Hverfisfljót.

under ice eruption iceland flooding
Electrical conductivity of the water increases due t geothermal activity in the area. Picture via mbl

Residents and passersby in the area are encouraged to remain diligent. Flooding over the riverbank and across nearby roads is possible in the next few days.

Additionally, the concentration of hydrogen sulphide from glacier runoff to the river is so high that it may damage the mucus membranes of the eyes and respiratory tract.

Cracks are also able to quickly form around Vatnajökull at this time. Tourists are therefore encouraged to avoid this area as well as Skaftárjökull, Tungnárjökull and Síðujökull where running water may come to the surface.

under ice eruption iceland flooding
Water measurements along the rivers flowing out of the Vatnajökull glacier. Picture via MBL

Vatnajökull glacier and volcanic activity

Vatnajökull, literally “Glacier of Lakes”, is the largest and most voluminous ice cap in Iceland, and the second largest in area in Europe.

Vatnajokull national park
Map of the Vatnajokull National Park. Grida

Under the ice cap, there are several volcanoes. Eruptions from these volcanoes have led to the development of large pockets of water beneath the ice, which may burst the weakened ice and cause a jökulhlaup (glacial lake outburst flood).

It is well-known that the Vatnajökull volcanoes continue to erupt beneath the glaciers, resulting in many documented floods:

  • One jökulhlaup in 1934 caused the release of 15 km3 (3.6 cu mi) of water over the course of several days.
  • The volcanic lake Grímsvötn was the source of a large jökulhlaup in 1996.
  • On 21 May 2011 a volcanic eruption started in Grímsvötn in Vatnajökull National Park at around 7 p.m. The plume reached up to 17 kilometers (11 mi).

During the last ice age, numerous volcanic eruptions occurred under Vatnajökull, creating many subglacial eruptions. [MBLGrapevine]