When I planned to write this article about the current states of Iceland I only wanted to write about Katla and Öraefajökull. But, as things turned out a third volcano got my attention.
In the end this article will be about how hard it can be for a layman to see what is important and not when overwhelmed with the plethora of information that is available for our beloved Icelandic volcanoes.
On the importance of importance
Not all volcanic signals are equal. And not all volcanoes are behaving the same prior to an eruption. Some volcanoes like Bárðarbunga are incredibly noisy between eruptions, prior to eruptions and during eruptions.
For Bárðarbunga it is a completely ordinary thing to throw a moment-magnitude earthquake of M5 with a follow up consisting of a heavy earthquake swarm, without it being a sign of an impending eruption. If the same thing happened at a more quiet volcano of the same size and capability, like for instance Grimsvötn, it would be time to run for the hills.
It’s the same with uplift and inflation, what would be big news for one volcano would just be a yawn for another volcano. If for instance Askja would be inflating at the rate and persistency of Iwo Jima it would also be time to run like a bat out of hell. At some volcanoes a few centimetres is a tell-tale sign, whereas at some volcanoes hundreds of meters are normal.
Some volcanoes are consistent stinky gas bags at all times, while others barely fart even during an eruption.
This is why it is so important to know your volcano well before trying to understand what it is doing. And, this is also why new data can be misleading as it comes to light.
Katla is quite likely the grand volcanic master of producing fake news, only rivalled by Yellowstone. Anything, including figures on ice cream consumption, will inevitably lead to war time headlines belting out that it is about to explode and destroy life as we know it.
Before we start with the latest news I would like to state the state of this volcano.
For as long as we have been able to instrumentally track and record this volcano it has suffered from intermittent intrusions visible on both seismometers and GPS-stations. Problem here is that it has not erupted for a long time, so we do not know that well how an upcoming eruption would look like, due to lack of anything to compare with.
All we know is that it is at times a rather noisy volcano, and that it can withstand a lot of big intrusions without erupting. A qualified guess, based on historic records from previous eruptions, seems to indicate that the last couple of days prior to an eruption would be quite memorable. So, expect to see something close to what you saw at Bárðarbunga prior to onset of eruption.
That means hundreds or thousands of earthquakes per hour with, some reaching up to M5 in strength.
Now let us turn to the latest news item. A group of scientists published a paper on measurements of free air CO2 released by Katla. The results are really intriguing since the values was quite literally sky high.
As far as we know Katla is ranking in at number 3 in the world in this regard. This is an anomaly in and of itself, since figures that high are normally associated with calcium-carbonatite volcanoes, or volcanoes that are erupting through heavy layers of carbonatite bedrock.
There is obviously no carbonatite lava in Katla, so we have to look for some other solution to explain where all that CO2 is coming from. My personal guess is that it is a function of fresh basalt percolating through a slab of oceanic crust partially consisting of calcite.
We all know that as you heat crushed calcite to produce cement you get an enormous release of CO2, cement production is the second largest source of manmade CO2 after consumption of fossil fuels. We also know that oceanic crust contains quite a bit of calcites.
What we know is that CO2 normally is an indicator gas pointing towards that magma has moved closer to the surface, so the world press jumped on the band wagon that his meant that Katla would explode hugely in the next couple of weeks. Problem is just that Katla has probably had a tremendous output of CO2 for millennia.
But here is the thing, we do know that the magma has risen closer to the surface lately, so a small part of that CO2 is probably related to an upcoming eruption. What the world press forgot is that even though that part is true, we are not actually seeing any signs that an eruption is close.
In Katla’s case we would see a tremendous amount of earthquakes for a few days coupled with rapid intra-caldera inflation. At least if it will erupt in the normal way through a caldera vent. If instead we get a rifting fissure eruption the noise level would reach unprecedented levels recorded in volcanology and there would be very funky GPS movements to the NNE of Katla proper.
But right now all we can say is that Katla will erupt one day. That is after all what volcanoes do. What we can’t do is accurately forecast when the volcano will erupt, since there are no current signs for an upcoming eruption. But, we will be able to forecast the eruption in time to give warnings to the local residents.
This easy to pronounce Icelandic volcano is currently my main cause for concern. In case anyone from the press is meandering about I should probably state that as far as we know today, the upcoming eruption is quite some ways away.
At the same time the current level of activity has never been seen at this volcano. We do though know from historic records that this volcano is quite noisy prior to an eruption, so what we are seeing is nothing at all compared to what will be visible on the seismometers when the volcano erupts.
After being dormant and almost entirely quiet since the last eruption in 1728 the volcano started to show signs of re-awakening in June 2017. To explain what we are seeing I need to fire off an analogy to put things into perspective.
What we are seeing is a heavy weight boxing champion waking up on a match day. The signals we have seen is the first initial fluttering of the eyelids. We have not yet even gotten to the first yawn prior to the morning cup of coffee.
In other words, do not expect The Rumble in the Jungle starting tomorrow.
The reason for me being so interested in Öraefajökull is it’s eruptive history, as far as we know every single eruption after the last ice age glaciation has been a VEI-5 eruption. In 1362 it belted out a major VEI-5 eruption, and the one in 1728 was a minor VEI-5, and as far as we can see all other eruptions has been around the same power level.
During the two last eruptions the residents near the volcano was wiped out completely, making this particular volcano Iceland’s deadliest volcano after Grimsvötn. And today there are once again residents living near the volcano. This is why this is a volcano that science is not allowed to misjudge prior to an eruption.
That being said, I am confident that science will accurately forecast this volcano in time to perform a mass evacuation.
The thing that makes this volcano so dangerous is that it is old, and that it erupts far apart in time. This has led to the magma fractionalizing at a high degree leaving a large reservoir of rhyolite. And as fresh basaltic gas-rich magma intrudes into that reservoir it will in turn expand.
Gas rich rhyolite has a tendency to erupt violently at the best of times, but in this case there is a lot of glacial ice, and as that melt it means that there is ample amounts of water at hand to further increase the level of explosivity.
During an eruption air travel between Europe and the United States would become impossible, and the weather in the northern hemisphere would be affected.
What I find interesting is how relatively smooth and persistent the increase in seismic activity has been. In June 2017 we saw 13 earthquakes larger than M1.2, and last month we saw 25 earthquakes larger than M1.2. Compared to Bárðarbunga this is of course a pittance, but the trend is clear. Magma is at a steady rate entering the magma reservoir and it is showing quite nicely on the GPS-plots.
So far we have not seen any large earthquake swarms, and we know that prior to an eruption the swarms will be continuous and contain earthquakes large enough to topple houses. At least that is what we know from written historic records.
Without giving any firm timeframe I say that it is a safe bet that we will over time see earthquake swarms developing, that in turn will increase in size, duration and energy level. Between these we will see the background seismic level increase.
So far this is almost a picture perfect start for the ramp-up period prior to an eruption. And as time progress we will be able to produce better forecasts, because all we can say now is that this volcano will erupt again in a not too distant geological future. And with geological future I mean anything from a month to a century in this case, with a month being highly unlikely at the current state of affairs.
Now that we have discussed two volcanoes that we can forecast days, or even weeks in advance, it is time to go to another extreme. A volcano only possible to forecast an hour in advance, at best.
In some ways Hekla is the most boring volcano on the planet, since it is not giving away a lot of information before erupting. At the same time this just increases the mystique for the true volcanic connoisseur.
Between eruptions all we see is a slow and steady inflation without any spurts of activity, it is almost like watching paint dry on a wall. You know it will be finished sooner or later, and that the result will be pleasing, still it is quite boring to look at.
The same thing goes for seismic readings from the seismometers. Now and then you get a couple of earthquakes, but not more than 5 or so a month. None of them are big, none of them are really significant in any volcanic way.
And let’s not even get into measuring gases. Your Friday ale is more interesting than Hekla when it comes to producing gases between eruptions.
In regards of Hekla we can’t even complain about not having an instrumental record of how it behaves prior to an eruption, because we have two good ones. And those two are stunning examples of pretty much nothing.
The only thing we know from those two is that roughly 60 minutes prior to an eruption there will be a small spattering of minor earthquakes, and then the mountain pulls apart and the gates of hell opens up in vivid colours and fury.
In the end what makes Hekla such an enigma, and such an interesting volcano to watch, is that everything has significance. A small earthquake can at any time get a few friends and fire and fury unleashes a few minutes later. Any earthquake can truly be The One.
Today the monitoring network around Hekla is 10 000 times more sensitive than during the eruption in 2000. This means that we see quite a lot more earthquakes, both smaller and at greater depth and in far more detail.
This time around we should be able to pick up what the signs and portents prior to a Hekla eruption are. Hopefully and perhaps.
One of the guesstimates is that prior to onset of an eruption we should see a few deep earthquakes between 25-30 kilometres depth heralding influx of fresh magma at depth. According to the guesstimate these should be almost directly below Hekla proper. And from 2011 the network has been sufficiently sensitive to be able to pick up those deep earthquakes. And on Tuesday two of them appeared.
Let me be the first one to state that there is a bit of conjecture that an eruption at Hekla would be heralded by those deep earthquakes. But Eyjafjallajökull 2010, Grimsvötn 2011 and Bárðarbunga 2014 was indeed heralded by such earthquakes. At those volcanoes it took between a year to several weeks before the actual eruption occurred.
We do though know two things about Hekla, it is an open conduit system, and we also know that the fastest speed with which magma has ever risen in Iceland is 2 kilometres per 24 hours, so if we would accept those figures the fastest possible time to eruption counting from today would be in ten days.
I am obviously not stating that Hekla will erupt in ten days, it might be in ten minutes or in ten years. I was just guesstimating the fastest possible time that fresh magma at depth could cause an eruption.
Those two small deep ones has since been followed by another 3 minor earthquakes at depth between 1.5km and 10.7km. The most shallow earthquake was probably caused by the weight of the mountain causing downwards pressure, and the one 5km is probably near the magma reservoir. But the most recent one occurred at 10.7km and may in some respect be associated with an ongoing intrusion.
Hekla is absolutely infuriating. I suffer from an almost perverse pride in my ability to accurately forecast Icelandic volcanoes based on scientific theory and raw data. Bárðarbunga was easy, I had that lamped a year prior to the eruption, and accurately predicted when and how it would erupt days in advance. For Hekla I might as well don a robe and rub tea-leaves on my bald head and go about chanting. So, all I have written above about Hekla is conjecture at best, but still a scientific conjecture based on raw data and a tea-leaf toupee.
If we now look at Iceland as a whole and try to see which volcano will erupt next time we have two well known candidates, and only one of them is on the list above. Grimsvötn is the most likely, but currently it is a bit far off from erupting according to data, so Hekla would be the best candidate for the next eruption.
But after the likely culprits of Grimsvötn and Hekla the field is surprisingly open. Katla is not a bad bet for an eruption in the next decade, but it might hold out a bit longer.
Öraefajökull is the big unknown, currently it is ramping up nice and slowly and should at the current rate also erupt in the next decade. Problem is just that the current and ongoing intrusion of fresh magma might stall, and it could take a few decades more until it is ready.
The conclusion might be unsatisfying, but in the end all we can say is that deep into the future Grimsvötn will erupt a couple of times, and that a couple of other volcanoes will pop an eruption. Perhaps not so bad after all, there is fire and fury looming in the distance as volcanoes do what they do best, erupt.