Today commenter Islander brought to my attention some news that the Icelandic volcano Katla seems to be picking up activity. But what is actually all the hoopla about really?
Katla is as most of you know one of the larger volcanoes on Iceland, but not the largest. The largest volcano on Iceland is the far less known Bárdarbunga volcano. Katla has been dormant since 1918, with the possible exceptions of small hydro magmatic events during 1955, 1999 and 2011. The hydro magmatic events are though not entirely proven to even have happened.
Katla has a 10 by 14km caldera that seems to have been formed during a minimum of two large VEI-6 eruptions. The volcano is covered by Myrdalsjökul glacier. During eruptions the volcano emits copious Jökulhlaups (water discharged as the volcano melts the glacier) and they are the single greatest threat from this volcano. Normally Katla has eruptions that range between VEI-3 to VEI-4, with larger eruptions happening after longer times of dormancy. Katla has had two large flood basalts after the ice age ended, the 5 500BC Hólmsá Fires and the Eldgjá eruption, both of them where following NW rifts trending roughly towards the larger volcano of Grimsvötn.
Earlier today (2012-09-29) the geologist Kristin Vogfjörð appeared on Icelandic Radio reporting that during the 24th of September a set of deep earthquakes had happened under Katla and that is considered as a sign of an increase of the risk for an eruption. She carefully avoided making any predictions.
So what happened then? Late on the 23rd 6 earthquakes ranging between 0 and 0.5M happened at depths ranging from 30 to 20 kilometers. On the 24th two more earthquakes occurred at 26 kilometers depth at the same location, those two where 0.4 and 0.7M respectively. The area is in the eastern part of the caldera.
Normally I have a deep respect for Icelandic geologists, but this is just so much hot air blowing. First of all the earthquakes are so minute that the amount of in-fluxed magma can comfortably be counted in wheelbarrows. It is like taking a piss in the ocean.
There was no associated tremor pointing towards magmatic movement of any significant scale. There is also absolutely no visible motion on the GPS stations surrounding Katla. Even at worst and these earthquakes where just precursors of a later influx we are still talking about years before an eruption taking place, and one should remember that Katla has had no less than two significant influxes of magma during the last 13 years without erupting. This so called “news” will only bring out the Katla fearmongerers, without anything having happened really.
This idylic scene is from Lake Tondano situated within the 20 by 30km Tondano Caldera.
Some volcanoes just can’t catch a break. Imagine for a little while that you are a bona fidé supervolcano. You are the largest of your type on the planet, you are highly active, and by gosh you have shown what you are capable of. In a perfect world your 20 by 30 caldera explosion should have put the world into awe, and the 1 000 cubic kilometer of DRE you ejected in the form of pumicious tuff covers an entire sub-continent. Yepp, you really did reach the small highly exclusive club of VEI-8 volcanoes. You smirk at your little sibling Monte Sommas antics with Vesuvius. Your Vesuvius event left a 3.5 by 5 km God honest caldera on its own. To top it off you have a huge underground reservoir of liquid acid that would seriously alter the planets weather if you felt like discharging it. You are also perfectly located to have a maximum kill ratio. So, you wake up and stretch your arms and start a double eruption from two different sub-volcanoes just to celebrate the new day. You have your largest eruption in recorded history. Then you look around to see the fearful faces of the residents as they offer up motorcycles in your name, you expect volcanologists doing somersaults as they play lip banjo, and literally thousands of blog pages glorifying your power and shear awesomeness. What do you find? Yawning people and a cockerel trying to wake up a pig sty. You find that for being an erupting supervolcano you are a massive PR failure. One single small earthquake at Yellowstone outperforms you in publicity.
Tondano
Compund satellite image/map of the Tondano area courtesy of JPL.
The quarternary volcano of Tondano in northern Sulawesi (Indonesia) had its massive caldera event about 2.5 to 2 million years ago. Technically it is a somma type volcano, complete with the remnants of Pangalombian, a former stratovolcano that disappeared in a Vesuvian VEI-7 total caldera event.
Parts of the Pangalombian caldera were later covered by the now dormant Tompaso volcano that ejected large amounts of basaltic andesites in a long series of VEI-6 eruptions.
Todays Tondano is known for having acidic maar eruptions inside the caldera, a couple of mud volcano events during recorded history and no less than 4 active volcanoes, Lokon-Empung, Mahawu, Sempu and Soputan. Quite often Lokon-Empung and Soputan have tandem eruptions.
Lokon-Empung
Lokon-Empung is a double coned strato-volcano located at the northern rim of Tondano. Lokon is a flat topped probably dormant volcano that no longer exhibits a crater on top and Empung is a historically active volcano that last erupted 1775. From 1829 onwards the site of no less than 25 eruptions has been Tompaluan, a smaller double crater situated in the saddle pass between Empung and Lokon. It has erupted since 2011 in tandem eruption with Soputan. The tandem eruption before that occurred on the 13th of May in 2000.
The current ongoing eruption is slowly working its way to becoming a VEI-3 eruption. But it has so far mainly been consisting of small explosive ash eruptions so it takes time to reach that level.
Soputan
This small stratovolcano is located on the southern rim of the Tondano caldera. It is part of trending line of ring dyke vents that formed in consequent eruptions ending with the formation of Soputan stratovolcano. It normally erupts from either the flanking vent of Aeseput or through the unusually large summit crater that pretty much has the same width as the top of the stratovolcano. This is of course a sign of a very young volcano with a highly potent vent system.
The current eruption consists of ejections of small to moderate explosive ash plumes. The ash columns according to the Darwin VAAC have been up towards 12.1km, with several slightly smaller columns reaching 9km height during the last few weeks. Smaller explosive ash plumes have been pretty much ongoing for the last 3 months now. This eruption is quickly ramping up to becoming a VEI-4, and is as such the largest sub-aerial eruption since Grimsvötn 2011 and that is without even counting in Lokon-Empung into the picture.
The system
As any volcano capable of a large caldera event Tondano has a large and intricate internal plumbing. It is believed that there is a very large reformed magma chamber at depth. As pressure increases in that magma chamber when new hot magma arrives it is believed that the magma either goes up into the caldera as emplacements, and that those sometimes cause maar explosions or reheats the very active thermal fields contained within the caldera. Or that the magma is pushed up into smaller sub-chambers under the active rim volcanoes. When that happens eruptions normally follows very rapidly. A sign of the rim volcanoes being systemically interconnected somehow is that Soputan and Lokon-Empung on many occasions has had eruption interspaced with mere hours.
As any Somma volcano the Tondano caldera is highly intricate and complex, and still it is surprisingly badly researched. The only good material is an Icelandic funded study on the possibility for hydrothermal energy plants in the region. Yepp, the Icelanders are going international with their knowhow.
Why it won’t happen
Image by Andreas / AFP – Getty Images. This image shows how relatively close the volcano is to villages, the height of the ash column and at the same time that the base of the ash column is equally wide to the width of the top of the volcano of Soputan.
For those who dream dark dreams about enormously destructive eruptions Tondano is a bad bet. Why? Tondano has it all really, large magmatic influx, steady inflation, a large central chamber, active volcanism. Pretty much everything that it should need for a VEI-8 eruption. Except for 3 small things, it does not any longer have the amount of water necessary to drive an eruption like that. As many of you know water is a large part of large caldera events. When Tondano went massively caldera it was situated pretty much at ocean level, so as the final large eruption (probably a large VEI-7) happened and the top of the caldera slumped inwards the ocean roared in and what is probably the largest steam explosion happened. Think of it as hundreds of Krakatau eruptions happening at the same time, and you have the picture. As time has passed the land has been lifted due to tectonic uplift.
Second thing is that the magma before the massive caldera event was highly crystallized rhyolites. After the eruption the magmas have been predominantly alkali basalt-andesites.
And the third reason is that Tondano is very well vented as long as the rim volcanoes are connected to the central magma chamber. As soon as the pressure gets above a certain level the magma squirts into the sub-chambers and the volcano on top erupts.
To put it simply, Tondano is a champagne bottle with 5 bottlenecks. The cork is well fastened on top of the actual central chamber, so it cannot erupt that way. Then it has one volcano with the cork slammed back fairly well (Sempu), but that is not fully dormant. One that has the cork put lightly back on (Mahawu) and two bottlenecks that haven’t seen a cork for hundreds of years.
Basically, the pressure is almost constantly being released by Lokon-Empung and Soputan, and if that is not enough Mahawu erupts too. Last time Mahawu erupted with another of the volcanoes it was Lokon-Empung in 1958. Currently even if pressure got really high the only thing that would happen is that all 4 volcanoes would go off.
The only risk for anything really interesting happening would be if one or two of the vents got blocked off. Even then no caldera event would happen, but the likelihood of a Vesuvius event would increase a lot. Currently the candidates for that is either Lokon-Empung or Soputan. Soputan seems to have a very wide bore caliber vent so it could probably release the pressure without exploding from the face of the planet. But Lokon-Empung has evolved quite a lot more, and as it has grown older the vent has narrowed down considerably. If Lokon-Empung was subjected to high pressure it would probably not be able to handle the stress and subsequently go off with a VEI-6+. This is though not likely at current geological timescale.
The only real risk is that a magmatic emplacement will happen in, or around the large reservoir of sulphuric acid (water with a ph of 2). I think anybody can imagine how un-nice a maar event, or even worse, a phreatic explosion, would be if it happened to cubic kilometers of liquid acid. First of all it would make northern Sulawesi uninhabitable and kill off large portions of all life there. And a phreatic explosion would severely hamper the world weather for quite some time. Not a nice thought is it, an acid caldera event. I would decidedly not want to be around if that happens.
Tondano today
Lokon-Empung belching out a 3km ash column.
For being a highly active volcanic region with at best medium risk of fatalities the volcano is surprisingly badly monitored and highly under-studied. Almost all I have written is from one study alone, and that was produced by Orkustöfnun as a part of the geothermal engineering program. Interestingly that report predates the recent article in Nature about a new tectonic plate forming next to Sulawesi. You can clearly see the rift fault in one of the maps in the PDF. Nature seem to have done a bad background check on their paper before publication.
In reality if we look beyond the doom and gloom prophecies of a large caldera event volcano the risk is the bad monitoring. The area is heavily populated and an unexpected VEI-4 eruption at a flanking vent, or lahars, or pyroclastic flows will kill people, potentially a lot of people.
A thought
When a volcano of this size erupts and the world’s volcanologists, volcano-bloggers, and generally the large number of volcano aficionados yawn and continue to look at other less interesting volcanoes that is not even erupting, then something is a bit wrong. I happily admit that it took me almost a week before I actually got around researching the volcano. Then my jaw dropped and I started doing somersaults while playing lip banjo. It is just the sad truth that there are more well known supervolcanoes in the predominantly white western world that steal all the attention.
While we sit and moan about there being no interesting eruption we did not even reflect as we read that two more volcanoes in Indonesia erupted simultaneously 30km from each other. The only comments about it was that people rode their motorcycles inside an ash cloud to get to and from work (Lokon-Empung), and that a rooster cackled at a video of Soputan barfing up a 9km ash column. Then we went back to looking at out Katlas, Heklas, and the rest of the non-erupting volcanoes. Indonesian volcanoes could do with a good PR-Agency.
This image from the tourist bureau gives quite a good perspective on the island of El Hierro and La Restinga. One just need to lift the eyes to see the volcanic edifices looming over the villcage.
As the smoke starts to clear at El Hierro we get a much more detailed picture of what is happening. As data has poured in we can now deduce a few things.
First of all GPS figures today confirmed that this is indeed a fourth bolus of magma coming up from the depth. The first one in July 2011 started the entire hubbub and in the end caused the sub-aquatic eruption south of La Restinga. A second bolus in January that followed the same path revigorated the ongoing eruption briefly, but was too small to keep up the pressure in the volcanic system and the eruption dwindled to a halt. The third bolus is so far the most interesting, during a few days more magma arrived than during the first one that caused the eruption. The magma arrived at the same place as for the first two (around the Tanganasoga volcano), but then it took an entirely new path and created quite a few earthquakes as it moved towards the western point of the Island. The fourth bolus also arrived at Tanganasoga, and immediately started to move south and slightly downwards.
Image by IGN. GPS data points for the uplift, figures are aproximatly 2 days old.
We still have only one set of data points for the GPS, but since it is visible on many of them it is still credible. What is a good test for if there is actual inflation or not is to check for motion in EW and NS directions. A false read normally does not show that.
The earthquake swarm is very vigorous with more then 100 earthquakes per day. The pattern is still continuing with a south and slightly down dipping motion. We will see if the hard tested village of La Restinga will have to suffer both the knowledge and the feeling of magma moving straight down under their feets.
Image by IGN.
We can also rule out any degassing or actual small eruption, what initially looked like harmonic tremor are most likely small earthquakes, there is no clear signal showing harmonic tremor to this date.
Image by IGN. No harmonic tremor showing on the charts now. So, no eruption, or no de-gassing.
There is no way to know if this bolus will cause an eruption or not. The lack of harmonic tremor says that it will at least not happen within the next 24 hours or so. But, for the residents on El Hierro the same advice is always valid, stay on top of the news.
The thermal hot spring bath of Balneario Pozo la Salud. Quite likely the new “to be at” spot for Jacuzzi watching.
The volcanic island of El Hierro is really turning into the Little Volcano that Could.
3 earthquakes seem to have changed the ballgame around once more. First came two deep earthquakes at a new spot at 10.10 in the morning, both of them at the depth of 20 km. 26 minutes later followed a 2.6M at 10 kilometers depth.
Within minutes a sharp increase was noticed in the high frequency tremor. The tremor lacks low frequency components making this a dead giveaway that we are seeing a de-gassing event. What has happened is that a persistent earthquake swarm north of Balneario Pozo La Salud most likely finally cracked through and things started to move up beyond the de-gassing threshold.
Image by IGN. Please notice the lack of tremor at the lower frequencies.
After the 10.36 earthquake the shallower earthquakes pretty much disappeared and we had an onset of a new active deep earthquake swarm. In retrospect it is clear that we most likely caught the arrival of a new bolus of magma arriving from depth. If so it is the fourth time new magma arrives from the depth.
The deep earthquake swarm roughly follows the same pattern as for the previous 3 arrivals. Activity started at 20 kilometers depth at Tanganasoga, and then moved outwards and slowly dipped deeper. Every arrival has taken a slightly different direction; this one is moving into what can only be seen as pristine territory.
Image by IGN. Notice the 10km swarm north of Pozo la Salud, and the arrival of the new magma at 20km around Tanganasoga, this time moving roughly towards La Restinga area with a slow dip downwards. Remember that it never went this way during the Eruption of Bob south of La Restinga.
It is still too early to see anything on the GPS, but it should start to be visible tomorrow.
Question then is where is the de-gassing happening? My guess is that the guests of Balneario Pozo La Salud might have an interesting wake up call. If they are lucky they will have a brand new hot water Jacuzzi out in the ocean. For those who do not know, Pozo La Salud is a thermal spring bath in El Hierro.
CARL
Friday riddle is still unsolved:
I am the stony product of music that make Pavarotti mate a canis canis sheep mixture, I am spawned out of the apothecary.
What am I? And what is my origin? 3 points to be had, 2 for the name of “What am I”, and 1 for the origin. There is also a cunningly hidden bonus point out there…
When Santorini erupts I will pack a particle filter mask, a mining helmet, goggles, a backpack full of water-bottles and book a room at Katikies hotell. Imagine sitting in this infinity-pool looking at the distant view of Nea Kameni as it farts out a slow and nice VEI-2. I will so do it.
Sometimes there is news about volcanoes that get blown out of all proportion. The island volcano of Santorini has unassumingly been erupting with small eruptions for the last 2 000 years or so. It is though mainly known for its VEI-7 Thera eruption 3 600 years ago.
Why do I mention the small ones? Well, a large volcano takes a lot of time to recuperate after a large eruption. First we need to understand what the large eruption was and what it did to the plumbing of the volcano. The Thera eruption started as a very large normal eruption that emptied out the magma chamber at rapid pace. In the end the roof of the chamber fell in on itself and water poured in. That in turn caused a very large steam explosion blowing away a sizeable chunk of the Island. One should remember that this is by far not the largest such eruption of Santorini, but thing is that they are far apart.
The effect of the collapse and the subsequent hydro magmatic explosion is that it left the volcano without a magma chamber. Where the chamber used to be there was only rubble. For the first 1 600 years after the eruption there was not even a chance for even a small normal eruption, any magma pushing up was deposited straight into the water filled rubble. In the end a solid roof started to build, and the cycle turned into the pattern we have today of small island building eruptions. Those eruptions are centered on the Nea Kameni Island with a few exceptions.
A few days ago Nature Geoscience published a paper on the current activity at Santorini. The paper itself was rather factual. Nea Kameni uplifted 14 centimeters from January 2011 to April 2012. That equals to 10 to 20 million cubic meters of magma. Sounds like a lot of magma does it not? We are after all talking about one of the largest active volcanoes around.
Well, the worlds combined press services though it was a lot. They picked up on it with war headlines.
Now let us look at it critically. The Italian volcano of Campi Flegrei inflated a bit in the 70s. It did 270 centimeters in less than half the time of Santorinis 14 centimeters without showing any other signs of erupting. After inflating 270 centimeters it went back to sleep, goes to show that it takes quite a lot for a supervolcano to go super if nothing else.
Now back to the magma chamber at Santorini and its size. The reason for Santorini having small and slow VEI-2s and a couple of VEI-3s and nothing bigger is that the chamber is still too small and weak to be able to withstand the pressure and volumes of a large eruption.
So, how about all that magma, it must be dangerous? No, not at all. Why? Because it is only 0,01 to 0,02 cubic kilometers of magma. If all of that jumped out of the volcano in one good eruption we are talking about a small VEI-3. Only problem is that all of it will not come up. Normally only one tenth to one twentieth of the magma comes to the surface from the chamber during an eruption. Bummer for all those who dream about gloom and doom.
So, taking that fact into account we are looking for 0,0005 to 0,002 cubic kilometers of lava coming out of the volcano. That is a midsized VEI-1 to a small VEI-2. Quite normal for Santorini really, the island has had a lot of them.
