Geology

An earthquake swarm hits the beast of a volcano Katla

By Staff

Mýrdalsjökull glacier Katla volcano is located under the ice cap to the right. The much smaller Eyjafjallajökull glacier is to the left (south). Photo by NASA Earth Observatory

A magnitude 3.3 earthquake struck in Katla volcano at 2.15 last night, followed by a few aftershocks according to the Icelandic Met Office (IMO). Katla is located under the ice cap of Mýrdalsjökull glacier in South Iceland and is one of the country's most notorious volcanoes.

In a great feature by world renowned volcanologist Haraladur Sigurðsson, published here on IcelandMag, he explains that history shows that Katla generally erupts shortly after its neighbouring volcano in Eyjafjallajökull glacier, in 960 AD, 1612 and 1823.

Read Haraldur's feature: Iceland's most notorious volcano is kept under close surveillance

Eyjafjallajökull's last eruption in 2010 was felt around the northern hemisphere when the dispersal of the ash cloud shut down all aviation across the North Atlantic for one week. 313 airports were closed and 104,000 international flights between Europe and North America were cancelled.

In his feature Haraldur says that no one knows if there is a connection between these volcanoes, or if this is just a coincidence. Katla has erupted at least 22 times since Iceland was settled 1,100 years ago, another eruption in the not-too-distant future is therefore inevitable.

As Haraldur points out the major problem with Katla and many of Iceland’s volcanoes is that they are generally capped by a thick ice sheet. All the highest mountains in Iceland are volcanoes, and they have accumulated layers of ice on top that may be 400 to 700 meters thick. When 1,200°C (2,192° F) hot magma rises up in the volcano beneath the glacier it causes massive melting of the ice and violent steam explosions. Normally, this magma would create relatively harmless lava flows on land, but the steam explosions in the glacier change the nature of the eruption to explosive, with production of huge volumes of ash that are dispersed widely in the atmosphere.

Katla has historically erupted at least once every century. As its last eruption was in 1918, geologists have been expecting it to take off for a while.

When Katla will eventually erupt it has, according to Haraldur, the potential of generating an eruption that is at least ten times larger than the 2010 Eyjafjallajökull eruption.

Although Katla is stirring, there is no need to panic. The volcano has sent us a similar reminder now and again for a while. But this beast of a volcano is certainly keeping geologists, volcanoes enthusiasts and Iceland's Civil Protection on their toes.