Glacial Outburst Flood Has Begun in Grímsvötn

Vatnajökull Grímsfjall Grímsvötn Bárðarbunga Kverkfjöll Jöklar Jökull Vísindi

A glacial outburst flood has begun in Grímsvötn beneath Vatnajökull glacier, experts have confirmed. An M4.3 earthquake at Grímsfjall this morning alerted experts to increased activity at the site. While such floods are known to increase the likelihood of volcanic eruptions, there are no indications an eruption is imminent at the site.

In an interview with RÚV, Professor of Geophysics Magnús Tumi Guðmundsson confirmed the glacial outburst flood began several days ago in the highland region. Elevated water levels have already reached inhabited areas further south, but they are not significant. “There is more water in Gígjukvísl river,” Magnús Tumi stated. “However, this is not a big event, it just looks like the summer water levels. It’s not a lot and it’s equivalent to a small or medium-sized glacial outburst flood in Skaftá river.”

Strongest earthquake in a long time

The M4.3 earthquake that occurred just before 7:00 AM this morning is “noteworthy,” according to Magnús Tumi. He says it’s “the biggest one we know of there for a very long time.” The earthquake hasn’t been followed by others of a similar magnitude, however, and appears to be a one-off event.

What is a glacial outburst flood?

Grímsvötn is an active volcano located beneath Vatnajökull, Iceland’s largest glacier. It has the highest eruption frequency of all the volcanoes in Iceland, but is located far from any inhabited areas. The geothermal and volcanic activity at Grímsvötn causes regular glacial outburst floods, known as jökulhlaup. Such outbursts are triggered by geothermal heating beneath the glacier which causes ice to melt, and eventually be abruptly released from beneath the glacier, into the surrounding water systems.

Magnús Tumi says Grímsvötn is now in a period of increased activity, which typically lasts between 60-80 years. It last erupted in 2011.

No Changes in Geothermal Activity at Askja Volcano

Michelle Parks / Veðurstofan. Dr Melissa Anne Pfeffer taking gas measurements at Askja.

There are no changes to geothermal activity at Askja volcano, according to preliminary results from a recent research trip conducted by the Icelandic Met Office. The land at Askja has risen 70 cm over the past two years, indicating that some 20 million cubic metres of magma are collecting under the volcano’s surface. An uncertainty phase has been in effect at the site of the remote highland volcano since September 2021.

Eruption on the way?

Volcanologists in Iceland have been predicting that Askja is preparing for an eruption in the near future. While uplift (land rise) has been occurring at the site for around two years, this summer local rangers reported that the temperature of the site’s geothermal lake Víti had risen. A plume of steam was also reportedly sighted at Askja this summer.

Plume of steam was likely dust

A group of scientists from the Icelandic Met Association led by Dr. Melissa Anne Pfeffer and Dr. Michelle Parks made a trip to Askja recently to collect data at the site, including gas and water samples. The preliminary results show no changes in gas or water from previous years, though the samples are being analysed futher at this time. There are no visible changes in the landscape and measurements of temperature and acidity do not indicate chanes in the geothermal activity around Askja and Víti geothermal lake. The report of a plume of steam seen at the site on August 12 has been interpreted as dust from a rock fall on the steep slopes of the caldera.

Askja is a volcano situated in Iceland’s central highland region. Its last eruption occurred in 1961 and gave clear warning in the form of strong earthquakes and a significant rise in geothermal temperatures. No such signs have yet occurred at the site. Tourism operators have nevertheless called for improved telecommunications at the site in case of an eruption.

Gas Pollution and Water Level Rise Near Mýrdalsjökull Glacier

Katla volcano

Hot water is flowing out from the geothermal system underneath Mýrdalsjökull glacier in South Iceland and conductivity remains high. Activity has, however decreased as compared to several days ago and there are no signs of volcanic unrest, RÚV reports.

An earthquake swarm was detected beneath the glacier last week, with the largest quake measuring M 4.4 and occurring on June 30 at 2:45 AM. Earthquake activity in the area has calmed since but continues nevertheless, with M 3.1 and M 2.2 earthquakes detected around 11:00 PM last night.

Gas pollution has also been detected near the site, and the Icelandic Met Office is warning travellers against being in the Katla volcano area due to the associated gas pollution risks. The Met Office also warns of a possible rise in water levels in Múlakvísl river due to the geothermal activity beneath Mýrdalsjökull.

Increased Geothermal Activity at Askja


Satellite images taken two days ago indicate increased geothermal activity at the bottom of Lake Askja, part of the Askja volcanic system in Iceland’s highland. Increased geothermal activity coincides with land deformation (uplift) and seismic activity in the region. There are no signs of an imminent eruption.

The Volcanology and Natural Hazard Group at the University of Iceland published a series of satellite images of Askja on their Facebook page yesterday, showing large thaw holes in the ice on the lake as compared to previous years. “The thaw holes that appeared [January 8] are big and can only be explained by increased geothermal heat in the water. That’s in line with the signs of uplift and earthquakes that have been measured (see Icelandic Met Office). So, it is therefore worth being vigilant about Askja these days.”

GPS measurements show that the land around Askja has risen about half a metre since August 2021, when monitoring began. The development has been relatively steady, with little seismic activity. In September 2021, the National Police Commissioner declared an “uncertainty phase” due to the uplift that remains in effect.

The last eruption at Askja occurred in 1961. It lasted 5-6 weeks and produced about 0.1km3 of basaltic lava, considered a moderate eruption. Askja lake is the youngest caldera in the volcanic system, occupied by a lake measuring 12km2 [4.6mi2] and 200m [656ft] deep. Askja erupts on average 2-3 times every century.

Larger Flood in Skaftá Imminent as Smaller Flood Subsides

On September 1, a small glacial outburst flood began in Skaftá river from the western Skaftá ice cauldron, which generally produces smaller floods than the eastern one. While the smaller flood is now declining, the Iceland Meteorological Office expects a flood from the eastern cauldron to be starting, which will likely reach the route 1 road along the south coast tonight.

Yesterday, GPS measurements from Vatnajökull glacier showed that the surface of the ice cap over the Eastern-Skaftá cauldron had started to subside. It had dropped by just under 1m [3ft] the 12 hours since the process started but will likely drop by 60-100n [200-330ft] once the cauldron fully drains. That indicates that the glacial meltwater will drain, producing a glacial flood. The last flood from the Eastern-Skaftá cauldron occurred in August 2018.

The latest data suggest that floodwater from the eastern cauldron will reach the hydrological station at Sveinstindur tonight. Based on earlier floods, it will reach its peak just over 30 hours after that. The first signs of the flood are expected to reach lake Eldvatn during the night or early tomorrow morning. Once it does, the river’s flow will steadily increase and likely reach its peak by route 1, late Wednesday night or early Thursday morning.

Initially, the water flows along a 40km [25mi] long tunnel below the glacier and then for 28km [17mi] along Skaftá before it reaches the first hydrological station at Sveinstindur, which will provide data on the increase in water levels. Earlier floods from the Eastern cauldron have reached 3.000 m3/s [105,944 ft3/s] but the last one in 2018 peaked at 2.000 m3/s [70,629 ft3/s]. The current flood from the western cauldron peaked around midnight, September 2 at around 520 m3/s [18,363 ft3/s], and the river currently flows at 412 m3/s [14,549 ft3/s]. Based on experience from earlier floods, the floodwater will reach the first hydrological station today.

Based on the current amount of water in the cauldron, it’s likely that the flood will be of a similar size to the one that occurred in 2018 but water could spread further as last week’s smaller flood has raised the water level in the river.

The Met Office will continue to monitor this event closely.

Possible hazards

Locals and people travelling in the area should be aware of possible hazards and conditions there.

  • In the next few days, Skaftá may overflow roads close to the river.
  • High values of H2S are expected near Skaftárjökull and people are advised to stay at a safe distance from the river and nearby glaciers.
  • Crevasses can form rapidly around the cauldron, so people travelling on Vatnajökull should stay away from the cauldrons and glaciers where floodwater is emerging.

Background information

The Skaftá cauldrons, eastern and western, are located in the western part of the Vatnajökull ice cap where geothermal activity melts the glacier from below and water accumulates beneath them. When the hydrostatic pressure is high enough for the water to lift the ice above it, the cauldron drains, causing a flood. Floods from the eastern cauldron are usually larger than the floods from the western cauldron. This phenomenon was first observed in 1955 and since then 58 floods have occurred. On average floods from each cauldron occur every two years.

The increase in electrical conductivity in the Skaftá river is probably due to steam explosions from the geothermal area beneath the ice cauldron. Steam explosions occur as the geothermal area adjusts to decreased water pressure resulting from the drainage of the cauldron. The explosions increase the amount of dissolved material in the floodwater, which is detectable downstream as conductivity increase in the river.

Fourth-Largest Earthquake in Bárðarbunga Since 2015 Eruption

Vatnajökull Bárðarbunga

An earthquake of magnitude 4.8 occurred at 3.54am this morning at the Bárðarbunga caldera in Iceland’s Highland. About a dozen aftershocks followed in its wake. The earthquake is the fourth largest in the area since the months-long Bárðarbunga eruption in 2014-2015. Experts say, however, there is no volcanic unrest in the area.

Elísabet Pálmadóttir, a geohazard specialist at the Icelandic Met Office, says it is common for Bárðarbunga to have isolated strong earthquakes like the one this morning. Such an earthquake occurred on January 5, with no follow-up activity. “We sometimes get earthquakes that are over M4, and then nothing else happens. Bárðarbunga often behaves like that.” Elísabet assures there is no sign of volcanic unrest in the area. “Nothing like it.”

Earthquake was larger than initial data suggested

The earthquake was larger than initial measurements showed. “We have an automated system that analyses earthquakes in real time and gives us a magnitude, but it was too low in relation to other data we were seeing, so it was obvious it had been much bigger. So we did the analysis again and got the magnitude 4.8, which makes it the fourth largest earthquake since the 2015 Bárðarbunga eruption. Since then there have been 12 or 13 small aftershocks, maybe around magnitude 1.”

Clear signs are likely if eruption is imminent

Magma is currently accumulating underneath the caldera, part of its regular activity. “When the eruption ended in 2015, then magma started accumulating again, in preparation for the next eruption, whenever that will be,” Elísabet explains. In 2014, seismic activity in the region gave warning of an imminent eruption around two weeks before it occurred. “Hopefully we get a clear sign beforehand like we got last time. We expect a bit of a heads up, maybe a few weeks in advance.”

No Magma Near the Surface by Grindavík

Þorbjörn efitr Pálmi Erlendsson Veðurstofan

The Icelandic Met Office has increased monitoring by Þorbjörn mountain on the Reykjanes peninsula. Land west of the mountain continues to rise, though gas measurements show no evidence that magma has risen near the surface. Land rise and earthquakes at the location suggest magma is accumulating under the surface, just north of the town of Grindavík.

“With increased monitoring, we are receiving more data in house which gives a clearer picture of the development by Þorbjörn mountain on the Reykjanes peninsula,” the statement from the Met Office reads. While land rise continues at a steady pace, gas and water samples from the area give no evidence that magma is near the surface.

Earthquakes can be expected to continue in the area, and the strongest of them near Grindavík. “The most likely explanation for this activity is a magma intrusion at a depth of 3-5km (1.9-3.1mi) just west of Þorbjörn. Most often such activity concludes without an eruption,” the statement closes.

According to geophysicist Páll Einarsson, if an eruption were to occur, experts would most likely be able to warn authorities hours in advance.

Geothermal Heat Exposes Glacial Cliffs

Fifty-metre [164 ft] high cliffs have emerged to the west of Grímsvötn volcano in southeast Iceland after having been covered by the Vatnajökull glacier for fifty years, RÚV reports. Geophysicist Magnús Tumi Guðmundsson says that increased volcanic activity and geothermal heat, not climate change, are responsible for the glacial melt that has recently uncovered the towering rock walls. The Icelandic Glaciological Society discovered the cliffs on a spring outing in the area.

Grímsvötn is located on the west side of Vatnajökull glacier and is the most active volcano in Iceland. Over the last few decades, its activity has increased, and the resultant heat has melted part of the glacier.

“If we’d talked about this twenty years ago,” Magnús Tumi continued, “I’d have said it meant that Grímsvötn would see [an increased accumulation of water]. What’s happened over the same time period, however, is that the geothermal heat has shifted such that water does not accumulate in Grímsvötn like it did up until 1996.” Magnús Tumi said this indicates that the melt that led to the cliffs being revealed was not triggered by global warming.

Researchers will better explore the cliffs once they’ve emerged more from the side of the glacier. “This is part of a caldera,” he continued. “These are steep cliffs. What you can see of the largest of them is at least 50-metres high. If this continues, they’ll be even bigger.”

Newly uncovered cliffs have been found in three spots around Grímsvötn, but Magnús Tumi says it may not be long before more show their faces. “There are cliffs that haven’t emerged yet that were named in the 50s, Depill and Mósar, which we’ll hopefully be seeing soon.”

Sulphur Smell by Sólheimajökull Glacier

Sólheimajökull glacier

A strong sulphur smell has been noticed in the vicinity of Sólheimajökull glacier in South Iceland, the Icelandic Met Office reports. No significant changes have been observed in hydrological, gas, or seismic data in the area.

Still weather in the coming days means any gases caused by geothermal activity can accumulate in higher concentrations. Individuals in the region are encouraged not to remain in low-lying areas where gas tends to accumulate and avoid proximity to Jökulsá á Sólheimasandur river.