One of Iceland's most extensive volcanoes is showing signs of restlessness. As reported by the Iceland Monitor, tremors beneath the southern Katla volcano reached magnitudes of about 4.6 at the beginning of this week, followed by another series hitting around 3.3M. These tremors could indicate that magma is rising up through the crust and fracturing it, but according to geophysicist Gunnar Guðmundsson of the Icelandic Met Office (IMO), there are no concrete signs yet of magmatic ascension.
Small effusive episodes do occur at Katla on a semi-regular basis, producing iridescent lava flows that are not particularly hazardous to anyone nearby, but it’s long overdue for a major eruption. At present, though, there’s no immediate danger of it happening.
“On average the time between eruptions is 50 years but now the volcano hasn‘t [significantly] erupted in 98 years,” Kristín Jónsdóttir, earthquake hazards coordinator at the IMO, told RÚV. “There will be an eruption, it‘s only a question of when.”
The mighty Katla has erupted at least 20 times in the last 1,000 years or so, but it has not erupted violently for about a century. Its last event, in 2011, was not powerful enough to break through the ice cap, the vast Mýrdalsjökull glacier – but perhaps next time, it will.
If it does, it is likely a huge, sustained ash column – something akin to the one that Eyjafjallajökull produced in 2010 – will be generated. More dangerously for Iceland itself, there is a possibility that the glacier will suddenly melt and cause catastrophic flooding to the valleys below.
The 2011 event caused flooding bad enough to sweep away a major bridge at Múlakvísl, without any fatalities. A more paroxysmal eruption, however, could produce something more devastating.
Katla, like all Icelandic volcanoes, is being closely monitored, and all technical equipment is currently being checked to ensure it is operating correctly.
Image in text: Katla explosively erupting in 1918. RicHard-59/Wikimedia Commons; Public Domain