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.

Grímsvötn Flooding Reaches its Peak, Begins to Recede

grímsvön flooding

The flow of the Grímsvötn glacial flooding reached its peak yesterday morning and has begun to subside. 

The flooding is caused by melting glacial ice from the volcano Grímsvötn, which rests underneath one of Vatnajökull’s ice caps. Glacial flooding from this volcano system is a regular event on Iceland’s south coast, and the most recent round of floods has not caused any significant damage to infrastructure.

Since last night, several earthquakes have been registered at Grímsvötn, but the Meteorological Office reports that there is no significant increase in seismic activity or threat of eruption.

In total, the ice sheet has sunk some 15m, indicating the volume displaced by the flooding. At its peak, the flow from the glacier reached 500m³/s, a level that is not considered to pose any significant risk to the region. Travellers to the south coast may, however, have noticed swollen rivers over the weekend.

Grímsvötn is one of Iceland’s most active volcano systems, with eruption cycles average 5-10 years. With Grímsvötn’s last eruption having taken place in 2011, it may be soon due, but as of now, there are no immediate signs pointing towards and eruption.

Level of Uncertainty Declared over Glacial Flooding from Grímsvötn

Vatnajökull Grímsfjall Grímsvötn Bárðarbunga Kverkfjöll Jöklar Jökull Vísindi

Civil Defense authorities have announced a State of Uncertainty due to glacial flooding from Grímsvötn, a subglacial volcano under Vatnajökull.

The ice sheet has been measured as receding in the last few days, accompanied by increased seismic activity.

Grímsvötn, one of Iceland’s most active volcanoes, has an eruption cycle of 5-10 years. As its last eruption was in 2011, it could mean that it is due soon. Glacial flooding can also trigger subglacial eruptions, which has been known to happen at Grímsvötn.

The glacial flooding is expected to last for several days, but no structural damage is expected. Grímsvötn flooding has become more frequent in recent years, meaning that individual floods are milder and cause less damage to infrastructure.

Read more about Grímsvötn and the flooding at Iceland’s Meteorological Office.

Unusual Activity at Grímsvötn Volcano: Aviation Code Raised to Orange

Grímsvötn Gígjukvísl

The Icelandic Met Office has raised the elevation colour code at Grímsvötn volcano from yellow to orange due to elevated seismic activity at the site. The glacial flood from Grímsvötn reached its peak discharge yesterday morning. Seismic activity at the site has been increasing above the normal level for the past two days or so, and a magnitude 3.5 earthquake occurred at the volcano just after 6:00 AM this morning.

Despite strong earthquakes detected this morning, no volcanic tremor has been detected at Grímsvötn and no increases or changes in geochemical emissions at the volcano have been measured. According to a notice from the Met Office, the seismic activity “is possibly occurring due to the decreased pressure above the volcano, since the flood water left Grímsvötn sub-glacial lake. According to calculations from the Institute of Earth Sciences at the University of Iceland at least 0.8 km3 of water have drained from the sub-glacial lake.”

Grímsvötn volcano is located in the Icelandic highland, underneath Vatnajökull, the country’s largest glacier. It last erupted in 2011 and emitted about 0.8km3 of basaltic tephra. It erupts roughly once every ten years and the eruptions are accompanied by glacial floods such as the one that is currently winding down.

Read more about the glacial outburst flood at Grímsvötn.

Glacial Outburst Flood Will Likely Peak on Sunday

The glacial outburst flood, or jökulhlaup, which started when the ice sheet in the Grímsvötn volcano beneath Vatnajökull glacier began to melt 11 days ago, is predicted to reach its peak on Sunday. At time of writing, the Icelandic Road and Coastal Administration does not believe that the runoff will affect traffic on Route 1 in South Iceland, nor that roads will need to be closed.

As of Friday morning, the Met Office reported that Grímsvötn ice sheet had sunk over 27m [89 ft] and was flooding the Gígjukvísl river at a rate of 1600 m3/s [56503 f3/s]. The electrical conductivity of the river, which is an indicator of how much geothermal meltwater it has taken on, has also been increasing and was measured above 464 µS/cm on Friday. The gas concentrations along the perimeter of the glacier have been measured at higher than normal levels, but do not currently pose a danger.

In the past, eruptions at Grímsvötn have begun following a glacial outburst flood. Per the Met Office, “[t]he loss of the water from Grímsvötn lake reduces the pressure on top of the volcano and this can allow an eruption to begin.” This happened in 1922, 1934, and later, in 2004, when an eruption beginning three days after a flood began. In that instance, there were a series of earthquakes before the eruption. But no earthquakes have been measured around the volcano at present.