Icelandic volcanoes are once again on the brink of showing the world what they are capable of. Four of them have been suggested as possibly on the verge of eruption: Bardarbunga, Grímsvötn, Hekla and Katla. However, the latter is the one that looks most threatening.
This is no surprise for Icelanders. They are used to living in a restless environment, dominated by the relentless power of volcanoes. As a matter of fact, Iceland is the largest landmass exposed along the northern sector of the Mid-Atlantic Ridge, a submarine volcanic chain along which magma is continuously issued by vents and fissure, producing countless, quiet underwater eruptions.
Why has the volcanic ridge been able to emerge from Atlantic ocean waters, resulting in the formation of this huge volcanic island? The reason Iceland exists is that it has been built, over the past 16 million years, by the combination of ridge volcanism and a huge and persistent plume of magma rising from the depth of Earth’s mantle.
There is no other place on Earth that is so fully dominated by fire and ice, two opposing forces that ever so often clash with each other, just like it happened in 2010 at Eyjafjallajökull Volcano, when the explosive contact between uprising magma and ice from the volcano’s summit glacier triggered an explosive eruption. The ash column that ascended about 12 kilometers above the crater was due to magma being instantly turned into tiny silica fragments as meltwater started gushing into the volcanic vent. The Eyjafjallajökull eruption led to major air travel disruption in northwest Europe for six days in April 2010.
Two years later, Iceland witnessed another eruption, this time from Bardarbunga volcano, that lasted between August, 2014 and February, 2015. The eruption produced huge volumes of sulphur dioxide which had a major impact on air quality in Iceland. There was no effect on flights outside the country, thanks to very limited emission of volcanic ash.
Now, it seems to be the turn of Katla: this large volcano, partially covered by the large Mýrdalsjökull glacier, last erupted in 1918, but it has erupted 16 times since the 12th century. The repose interval between eruptions is about 55 years: moreover, eruptions the nearby Eyjafjallajökull in 1821-23 and 1612 were followed within months by eruptions of Katla.
Actually, in 2011, a flood from Katla’s glacier swept away a bridge along Iceland’s Ring Road, leading some volcanologists to suppose that the meltwater was caused by an eruption underneath the ice cap, that never made it to the surface.
What about the possibility of a major explosive eruption from Katla? Well, after 99 years from the latest one in 1918, we may say that, judged in terms of the historical calendar, an eruption may be regarded as “overdue”. Although we are aware that the geological calendar and the human one are extremely different, Katla may really be priming for eruption. In fact, the volcano has been restless in the past few months, with swarm of earthquakes detected underneath the volcano, some of which as powerful as M 4.3.
Volcanologists are aware that these quakes can be interpreted as possible indications of magma rising through the crust; nobody can predict, at the moment, whether magma will make it through Katla’s summit glacier and trigger a major outburst.
Federico Pasquaré Mariotto (Associate Professor, Insubria State University, Varese, Italy)
Corrado Venturini (Associate Professor, Bologna State University, Bologna, Italy)