Powerful Earthquake Swarm In Bárðarbunga, Scientists Are Cautious

The Civil Protection Department has declared an uncertainty level due to a powerful earthquake swarm that began in Bárðarbunga shortly after 6:00 on January 14, reports RÚV.

The swarm subsided by nine o’clock, but another could occur in the coming hours or days. Experts describe the seismic activity as unusual, with a likelihood that it is related to magma intrusion.

A natural hazard specialist at the Icelandic Met Office noted that this earthquake swarm resembles the lead-up to the 2014 Holuhraun eruption.

Seventeen earthquakes over magnitude 3, largest at 5.1

Bárðarbunga has remained relatively calm throughout the day and evening following the intense earthquake swarm between 6:00 and 9:00 yesterday morning. According to the Icelandic Met Office, the largest earthquake reached a magnitude of 5.1, with two others measuring around or above 4. In total, 17 earthquakes exceeded a magnitude of 3.

The swarm was located in the northwest part of Bárðarbunga.

This was the most powerful earthquake swarm since the end of the last eruption, which lasted from late August 2014 to late February 2015. The uncertainty level was declared at noon.

“At some point, there will be an eruption there — it’s just a question of when and where,” said Kristín Jónsdóttir, head of volcanic activity, earthquakes, and crustal deformation at the Icelandic Met Office, adding that the earthquake swarm is part of an ongoing process spanning the last ten years.

It is difficult to predict what kind of eruption might result from the process currently underway, said Kristín. The volcanic system is large and lies beneath Vatnajökull glacier but also extends beyond it. Therefore, an eruption could begin either beneath the glacier or outside of it. It could result in either an ash eruption or a lava eruption, not to mention glacial outburst floods.

Scientists remain cautious

“We cannot breathe easy just because the earthquake swarm in Bárðarbunga has now subsided,” says geophysicist Freysteinn Sigmundsson.

Freysteinn explains that there is increasing pressure in the Bárðarbunga volcano, with the most significant land uplift recorded in Iceland, according to calculations by Magnús Tumi Guðmundsson.

“Even though the [earthquake swarm] has stopped, for now, nothing has fundamentally changed. We expect magma to continue flowing into the roots of this volcano. That’s why caution is needed,” he says.

Freysteinn adds that this area likely has one of Iceland’s highest rates of magma production. He notes that even a small eruption beneath the glacier could have significant impacts, due to glacial floods and ash fall.

The most likely scenario is that magma is travelling underground from Bárðarbunga’s caldera before reaching the surface. Magma intrusions can take many directions and may surface either beneath the glacier or outside of it.

What’s Bárðarbunga?

At 2,000 meters, Bárðarbunga is the highest point in the northwest part of the Vatnajökull glacier. Beneath the glacier lies the caldera of the central volcano, which covers an area of 65 square kilometres.

The Bárðarbunga volcanic system stretches roughly 190 kilometres in length and about 25 kilometres in width. It has been highly active since the settlement of Iceland, with at least 26 eruptions occurring over the past 11 centuries. This makes it the second most active volcanic system in Iceland, after the Grímsvötn system.

The photo is from the 2014-2015 Holuhraun eruption.