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Iceland Mag

Geology

Monster volcano Katla keeps clearing her throat, a large earthquake hit yesterday

By Staff

  • Glacier lagoon at the edge of Mýrdalsjökull glacier Scientists are closely monitoring melt water flowing from the glacier. The magma chamber of Katla is 2 km (1.24 mi) below the top of Mýrdalsjökull glacier in South Iceland. It's Iceland's fourth largest ice cap covering 596 km2 (230 sq mi). The summit is at 1.493 m (4.898 ft) above sea level.

A magnitude 3.9 earthquake struck in Katla, the large sub-glacial volcano, at 13.31 (1.31 pm) yestarday, followed by a few aftershocks. However, there are no signs of volcanic tremors 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 feared volcanoes.

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.

Earthquakes in Katla started to pick up the pace earlier this summer. On 29th August two magnitude 4.5 quakes struck in the northern rim of the caldera. They are the biggest earthquakes in the volcano since 1977.

When asked what is going on in the volcano, Magnús Tumi Guðmundsson, professor of geophysics at the faculty of Earth Sciences at the University of Iceland told local news site Vísir that he is not loosing sleep over the situation. “We have witnessed several unusually large earthquakes, of magnitude 3 or larger. But their depth is rather shallow and we see no signs of expansion in the caldera or increase in geothermal activity,” said Magnús and explained that if those factors were occurring in addition to the quakes that would be a sign of the volcano starting to warm up.

Several similar periods of unrest have occurred at Katla in the last 50 years without resulting in an explosive eruption. The history shows us Katla is overdue, so we should be prepared. Here you can read IMO’s assessment.

IMO has several monitoring networks around Mýrdalsjökull glacier, the home of Katla, and via twenty-four-hour monitoring, every effort will be made to issue a timely warning in the event of a volcanic eruption.

imo_earthquakes_map_sept.png

Sub-gacial The green star shows the location of Katla volcano. The map shows the locations of earthquakes during the last 48 hours. Around 800 earthquakes were detected last week, 12-18 September, by the national seismic network of the Icelandic Met Office. Image by the Iceland Met Office.

The history of Katla
In a great feature by world-renowned volcanologist Haraladur Sigurðsson, he explains that history shows us 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. 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 other large volcanoes, is that they capped by a thick ice sheet. 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.

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.

Read more: A guide to Iceland’s glaciers, what to do there & their claim to fame

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.

The distance between Katla and Reykjavík is around 180 km (112 mi). However Vík village (population 318), a very popular travel destination on the south coast, is located at the bottom of the volcano.

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