Did you notice the erupting Supervolcano?

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 13^th 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.

CARL

http://www.os.is/gogn/unu-gtp-report/UNU-GTP-2010-03.pdf

Chain of Dead Poets!

Amsterdam Island with visible craters.

The Amsterdam St Paul hotspot is one of the weaker hotspots around. It has created the St Paul and Amsterdam Islands, the now active Boomerang Seamount (last known eruption 1995), and an elongated chain of seamounts called the Chain of Dead Poets. These are remnants of the eruptive wake of the Amsterdam St Paul hotspot as the plates move on over it. The hotspot has had 2 episodes of increased activity after it became active. The first period lasted from 10 million years ago to six million years ago. The second period started 3 million years ago and lasts up until today. Amsterdam, St Paul and the Boomerang Seamount have all been produced during this second period of activity.

The hotspot is associated with the South East Indian Ridge and its rift system, and the chains volcanoes show evidence of changing in its chemical composition as the hotspot moved into the SEIR.

Amsterdam Island

The Island is the northernmost of the Antarctic sub-aerial volcanoes. It has had two eruptive centers down the line. Both with visible craters, the younger of the craters are far more visible on the image. Both of the craters are from periods of heightened activity, but later volcanism on the Island has primarily been of the flanking fissure type. Even though no eruption has been witnessed lava samples taken from the flanks of the younger crater shows that the volcano has indeed erupted during the last 100 years.

St Paul Island

The channel into St Paul natural harbour. One should keep slightly to the portside of the centerline of the channel when sailing in. The starboard side is much more shallow. By keeping slightly to portside of the middle you can get a 3 meter deep sailing ship into the natural harbour, well inside of it depth is not a problem, and you are quite safe regardless of weather. Stay away from the mammals on the beach, they are big and mean and are in no way to be compared to people in bikinis.

The island had a large eruption a few years before 1780 in which the predominant caldera formed. Even though the caldera is small for being a caldera it was probably formed by a Krakatoa style eruption starting with a for the volcanic system unusually large eruption with a subsequent magma chamber roof failure that let the ocean water down into the chamber. The ensuing steam explosion gutted the chamber.  In 1780 the vestigial remnants of the caldera wall facing the ocean crumbled and the ocean has during the following years carved out a fairly broad, but shallow canal that is open for smaller sailing ships due to its limited depth of around 3 to 5 meters.

Map of St Paul Island from Wikipedia. Note that the island is very small. The actual caldera is only slightly larger than 1 km across.

The Island is together with Isle du Kerguelen the best harbor in the southern ocean, and many trans-globe sailors make a port of call for repairs, or just general relaxation and landfall.

Boomerang Seamount

Not much is known about Boomerang that lies 18 kilometers north of Amsterdam Island. It rises 1 100 meters above the sea floor, but is still 650 meters below the ocean surface. During an expedition in 1996 they dredged up a lava sample and tested its Uranium/Thorium content. It showed that the lava had been erupted only 5 months prior to the visit.

The Seamount has a 2km caldera showing that the volcano has had at least one substantial eruption and probably have been a bit closer to the surface before.

CARL

The Santorini Midget Lava Blob!

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.

Gosh darn, who stole my end of civilization?

CARL

Answers to Name that Lava XX and Alan’s Evil Riddle #13

 

Photographer, Fredric Alm. Used by explicit permission from LKAB. Remnants of the open pit mine with the mountain of Kiirunavaara cut in half on the right hand side. The city of Kiruna to the left on the brink of tumbling into the mine, and the lake in the top is situated on a second large orebody believed to be the actual old magma chamber, the ore body is named the Lake-ore and requires that the lake itself is moved to another location. Click on the image to view it in detail, it is well worth it.

The lava this time was from a sample taken from Kiirunavaara iron ore mine. It was a Kiruna type magnetite-apatite. Kiirunavaara is a very old volcano (1 900 million years old) of a very unusual type. It is situated within the Svekokarelian orogenic zone. The zone is filled with large ore bodies; the largest conglomerate of ore bodies is the Malmfälten (Ore-fields). It was constructed as very deep magma moved upwards from the core, forget mantle plumes, here we are talking about an actual core plume. That explains the ultra-pure ores in the area. It is normal with ores with an iron grade of up to 60 percent.

Kiirunavaara was in the 1870s a mountain 763 meters high, but in 1960 the mountain was gone and the mine went subsurface. Since then it has gone through 5 main levels, the fifth being at a record breaking 1 365 meters depth.

The magma intrusion formed a hangwall 8o meters thick, 4 000 meters wide, and with a known minimum depth of 2 000 meters, but with no known restriction at depth. As it goes deeper the ore body widens. Since the intrusion is slanted at 55 degrees angle the amount removed reaches more than 2 500 meters making the mine that largest and deepest iron ore mine on the planet. Since the start more than 950 million tons of iron ore has been extracted.

Photograph from Wikimedia Commons. The abandoned open pit mine at Kiirunavaara. Click to view the details.

It is prognosticated that the Malmfälten contains a reserve of iron ore that would guarantee the current production (5 percent of world consumption) for 250 000 years. That number is actually more mind-boggling than the scale of the operations in Kiruna.

Lonely Planet has put the mine in the highest category as a must to visit. The mine is open for visitors year round, one of the few open for visitors. It is a true Mecca for all rock nuts, volcanoholics and general mine fetishists.

The 540 meter level was used in the late eighties for growing ordinary mushrooms, but as prices plummeted the company that borrowed that part of the mine switched to growing Shii-take instead. The mine proved to be perfect for that particular mushroom. Since Shii-take is highly sporous it has pervaded into all parts of the mine through air ducts. So, at any part of the mine where there is light you can find Shii-take growing from the bare rocks, sometimes one can even find them on the machines. Today the mine is one of the top producers of this tasty mushroom.

Shii-take growing on a slab of iron ore.

There are two other large mines in Kiruna, both of them closed in the eighties during the world wide steel crisis. The Luossavaara Mine was of the same type as Kiirunavaara Mine, the ore body is probably connected at depth with the Kiirunavaara ore body. The other, Tuollavaara Mine, is a comparatively slender low-phosphor hematite ore. And with slender we are talking about 6 ore bodies that are on average 30 meters thick and 150 meters wide with unknown depth.

The entire city is now going to be closed down and moved since it is soon going to fall down into the hole created as the slanted hangwall caves in on itself and falls down into the mine. The same fate also awaits the City of Malmberget (Ore Mountain).

Economically it is one of the world’s leading power hubs. The area sprouts 4 operational mines on mammoth scale, among them the largest copper mine on the planet. And several more are being projected or are in startup phase to ensure a production yield of up to 20 percent of the world’s annual iron consumption. During the next 20 years a staggering 130 billion Euros are going to be invested in building new infrastructure, replacing two entire cities falling down into old parts of mines, and generally starting new mines and 2 new smelting plants. Income in the area is the highest in Europe and the city of Kiruna sports a 10 percent negative unemployment. The area has a gross municipal income surpassing many smaller European economies on a population of 35 000 deep frozen souls. The city of Kiruna also has its own spaceport and its own space program together with Virgin Galactic. In theory it would be a nice place to live in from a purely economic standpoint. Only problem is that the city resembles Mordor with a tinge of hell frozen over and then plunged into eternal darkness.

All of this due to the core having a burp 1.9 billion years ago, I am still curious about how that burp happened. It is a mystery that really should be solved; because I do not think we would like to be around if it happened again. The core contains a lot of not so nice stuff compared to the fairly friendly constituents of the mantle.

Russian Apatite, Wikipedia Commons. Click on the image for details.

The riddle was quite simply a rhymed word pun on apatite derived from apathy. Part of the poem was about it doing naught and being lethargic, the other part was about sitting in a chair as apatite sits in a matrix. Lair is of course the mine of Kiruna making the Riddle recursive of the Name the Lava competition with the Apatite-magnetite Iron ore. As someone said, it is easy afterwards. Here is the poem in orignal, and do not blame Alan for lack of poetic excuberance, I am guilty of it since Alan is on a mysterious walkabout.

I do naught,
I make naught.
Joyless in my chair,
deep in my lair,
I think naught.

CARL

El Hierro and the Physics of magma chambers

Image from Nature GeoScience. From Phillip A. Allens article Geodynamics: Surface impact of mantle processes.

Part 1

Not many people think about what is great with physics. People are normally more occupied with buying Prada hand-bags to carry their rat-sized yapp-dogs than physics. The great thing with physics is that the laws of nature are universal. And with that I mean that they can be transferred easily from the school books into real life, and from one part of science into another.

I am as most of you know not a volcanologist or a geologist, but I am a physicist. So every time I try to understand a volcano I do it from how it is behaving from the point of perspective of the laws of nature.

This time I would like to write about a few things regarding how magma chambers must be formed according to physics. I will mainly not talk about magma chambers because they are fairly hard to visualize since nobody has seen one in real life as it is forming. But most of us have for instance blown up a balloon.

In this case we will be talking about magma chambers that come from hotspot volcanism; the process will be slightly different in a subduction volcano. But first we need some background, this post will be about precisely that background.

Hotspots, weightlessness and Blobs

Let us start with what is required for a magma chamber to even start forming. And as a physicist I am always talking about basic forces. And there is only one basic force, and that is energy. There are of course many types of energy, and in this case we are talking about energy as mechanical pressure and heat.

Thankfully for the poor fledgling magma chamber there is one thing that causes both pressure and heat, and that is your basic magma. So, let us drop up a ball of nice hot juicy magma from the hotspot under El Hierro.

It is not entirely clear how magma travels upwards via a hotspot, but we know there are two types of hotspots. First we have the deep Icelandic type that brings up material from the depth, this magma is hot and arrives at high (relatively) speed and with great force. It brings with it an assortment of rare and heavy metals from deep down at the boundary between the core and the mantle. The other type is a colder and less deep hotspot. The magma here is either brought up from within the mantle, or created as the hotspot heats up material close to the MOHO boundary either through heat or pressure, perhaps even a mixture between them. This type creates magma that is low in precious metals, and gives a low Uranium-Thorium (UrTh) count which in turn is a dead giveaway that it comes from a shallow source. The Canarian hotspot seems to end up somewhere in the middle of these two types, it is definitely not melting crust as a part of the magma creation, the almost pure basic basalt tells us that, on the other hand it is not from the core/mantle boundary since the UrTh count is wrong for that option. Let it suffice to say that the Canarian hotspot is a bastard mongrel of a hotspot.

So, where does now the pressure to drive any hotspot come from? Well, once again the answer is not simple. We have at least two sources. The first is heat; the Earth is producing loads of juicy heat due to at least 3 different processes. The first one is UrTh and other atomic nuclear processes. Yepp, we live on an atomic reactor. The second one a form of pressure called overburden pressure. That is the combined weight of the planet pushing downwards, this creates compression heat. The third is through the dear old gravity slowly massaging the planet, this is by far the smallest of powers creating the heat. Here I have simplified a bit, there are more forces at play than this.

Image of nested magma.

So, how come then that magma travels upwards? The answer might surprise you a lot. If you are getting a headache from this it is normal. Let us imagine that you where hanging at the exact mid-spot of the planet. The pressure would be phenomenal from the overburden pressure; still you would notice something odd. For the first time in your life you would be completely weightless. This would be due to the entire planets gravitational pull would be affecting your entire body in every direction at the same time, effectively cancelling out any gravitational effect.

What does this now have to do with magma? Well, you have magma under tremendous pressure that does not weigh a lot. A cubic decimeter of magma at the mantle/core boundary is considerably more lightweight than the same volume of water. And at the same time it is squeezed by tremendous pressure.  Here we enter a nice little simple physics, when you squeeze a fluid it will try to run away, in this case it can’t go down, it is fairly buoyant and will try to float. Now we just need one small thing, a conduit. Enter the heat.

Energy will always go from a high state to a lower state; this is the nutty little physics law that also gives that order will always go towards disorder, in other words, entropy and enthalpy. So, the core will try to lose heat, and the heat will always be able to escape, and once a convective current of heat has started to run upwards it will jolly well keep on going. When magma finds a stream of heat going upwards it will follow that stream because the fluid will follow the point of least resistance. And that is why a mantle plume and a hotspot is the same thing (simple physics). The mantle plume cannot exist without a hotspot, and the hotspot will sooner or later create the mantle plume.

Now our blob of magma is finally moving upwards towards El Hierro, the trip started a long time ago, it takes a while to go through all that semi-permeable heated pipe that runs up through the mantle. One day, let us say on the 24^th of June 2012 our blob of magma arrives at the bottom of the crust under El Hierro.

The speed with which it arrives is very slow even compared to a human walking, but the weight is enormous, the same goes for the amount of heat energy and the buoyancy pressure. Let us just say that it is like a comet sized blow-torch hitting the almost melted MOHO boundary. It will cut through the first layers in a rather short time. As it goes on up through the bottom of the crust it decelerates fairly quickly, and that is the point where all the fun starts, the formation of the magma chamber.

Until the next time!

CARL