Olafur Ragnar Grimsson, Iceland's president, warned the world about Katla, another volcano much larger than Eyjafjallajokull which could erupt in the near future in an interview on BBC this week. He has been criticized by some of scaring people without any need, while others say that the world should be aware of the dangers.
So the question is, how likely is Katla to erupt and how dangerous will it be?
We don't really know much about volcanoes and how to predict an eruption. There are two factors we use for that. One is history and the other is seismic activity.
If we look at Katla's behavioural pattern through time, we have about 1100 years of eruptions that are documented. In this time, Katla has erupted 21 times. The last time it erupted was on October 12th 1918 though some say it did have a minor eruption in 1955 which never managed to melt the icecap. Either way, it's time for it to erupt again.
We also know that Eyjafjallajokull, the volcano that is now erupting and manage to ground all air traffic in Europe for several days, has erupted three times before since the settlement of Iceland in 874. That was in 920, 1612 and 1821. In all three cases the eruption was followed by an eruption in Katla within a few weeks or months. That is why many think it is very likely to erupt within the next 18 months or so.
There is one important difference in this eruption from the previous three. This time it did not start by an eruption in Eyjafjallajokull, but an eruption on Fimmvorduhals, a passage between the two volcanoes, Eyjafjallajokull and Katla. It hasn't erupted there in about 5.000 years. That could mean that some pressure has been released from Katla which would make it more unlikely to erupt now.
There has been now seismic indication of an eruption in Katla. We've had some seismic activity in the mountain for years but not enough to indicate an imminent eruption. We did how ever see some rise of the Eyjafjallajokull mountain and a clear increase in seismic activity so an eruption was expected any time now.
On the flood watch below Eyjafjallajokull - Golli/mbl.is
How dangerous is Katla?
Katla is a larger volcano under much thicker ice than the 250 meter thick ice in the Eyjafjallajokull crater. That means that the flooding following such an eruption is expected to be 50-100 times larger than the flooding from Eyjafjallajokull. A little river turns into a gigantic flood within a few minutes, but the flood is expected to reach the shore in just 45 minutes. The amount of water flowing down is estimated to be about 300.000
The effect on Europe
The effect the Eyjafjallajokull eruption had on Europe took everyone by surprise. One of the reason it was so vast is not the size of the eruption but the nature of it. The ash particles were exceptionally fine which means the spread much more easily by air. Winds from the north over Iceland and little wind over Europe was a bad combination for air traffic in Europe. Even though Katla may be a much larger eruption, the dust and ash particles tend to be larger than the ones we've seen in Eyjafjallajokull and should therefore not spread as far. The dangers for Europe in the event of an eruption in Katla are therefore probably less, than in the Eyjafjallajokull eruption.
The dangers for people in Iceland are also minimal. I live in Reykjavik, only 120 km west of Eyjafjallajokull and 150 km west of Katla, and I have not seen any smoke, ash or inconveniences of any sort because of the eruption. It has been very unpleasant for the farmers living right below the volcano, but that's about it. There is no reason to fear coming to Iceland. It's just more interesting being able to see the enormous forces of nature in action. This is how the planet has been shaped and created through millions of years. As Paulo Coelho put it on twitter:
Feel free to ask anything about the eruptions and volcanoes in Iceland and I'll try to find the answers for you.