Volcano Radio: From Okmok with Love

An electromagnetic whistler wave, from Palmer Station,  Antarctica. Source: wikipedia, Stanford VLF group

An electromagnetic whistler wave, from Palmer Station, Antarctica. Source: wikipedia, Stanford VLF group

Volcanoes are often inconveniently located in isolated and unpopulated regions. Of course, some of these regions are unpopulated precisely because of their volcano, or instead of unpopulated are depopulated, but that is a different story. When an area is devoid of people, there tends to be a reason. Modernity looks for and finds cheap and empty spaces for new housing developments. It doesn’t have time to wonder about the meaning of the words ‘Mississippi flood plain’ or why Ercolano sounds a lot like ‘Herculaneum’. Modernity also demands that we know about even fairly minor eruptions without delay. That is why we need volcano observatories. The case of the commercial airplane that lost its engines when flying into an unexpected volcanic ash cloud comes to mind. But how do you get instant data and messages from these forbidden places? The next newspaper delivery won’t do. In our modern world, it has to be by the fastest means available.

The answer is old-fashioned radio. It travels at the speed of light. Only the financial world needs things to move faster than that. (That also means they travel back in time. Explains a lot, really.) For people with less money, light speed suffices. Volcanology, and volcano observatories, depend on radio, both for hearing about eruptions and informing about them. Even the monitoring satellites communicate to us by radio. Radio is the original ‘wireless’. And now, volcanoes have joined the fray themselves. For the first time, a volcano has been heard announcing its own eruption by radio.

Radio Alaska

Source: wikipedia

Source: wikipedia

The Aleutian Islands are one of the most active volcanic arcs in the world. 35 active volcanoes are listed on the map above, from the Alaska peninsula to the many volcanic islands. Umnak Island, one of the largest of the Aleutian islands, is known by tourists for its geyser field. The southern part of the island has two rather beautiful stratovolcanoes, Mount Vsevidof and Mount Recheshnoi. The northeast side, almost a separate island, is dominated by the shield volcano Mount Okmok and its 9-km wide caldera, and is most impressive when seen from above.

Okmok caldera, northeast  Unmak. Source: wikipedia

Okmok caldera, northeast Unmak. Source: wikipedia

July 12, 2008, and it is 11:43 am, local time, on Umnak Island. Rather suddenly, Mount Okmok erupts and sends ash 15 kilometer high, in its biggest eruption since the 13th century (at least). It had been a fairly active volcano, with eruptions in 1997, 1958, 1948, and 1817, but the 2008 eruption was bigger. An hour later, an even bigger column forms. In the following weeks the eruption continues with plenty of ashy explosions but little or no lava. The rather wet caldera provides plenty of water for hydro-volcanic explosions. The five week, VEI-4 eruption leaves several Aleutian communities cut off during the height of summer as air travel is curtailed by the airborne ash.

Notably, the eruption got going with very little warning. There were some earthquakes in the hours before the eruption, but that was all and it had not been picked up as a warning. The volcano was monitored with real-time seismic and geodetic networks, but even so, for the real-time monitors it all happened too fast. The Alaska Volcano Observatory (AVO), normally very much on the ball, were told about the on-going eruption by the U.S. Coast Guard, who in turn had heard about it when being contacted by the ranch caretaker family of Fort Glenn (an old US military base) while they were fleeing from the ash fall – they escaped with the help of a fishing vessel. It shows the importance of having people on the ground to report events, albeit in this case unwilling participants who were too close for comfort.

The caldera after the 2008 eruption, with the main sites labeled. The new tuff cone has an 800-m crater at the summit. Source: http://www.alaskageology.org/documents/0809/AGSJanuary08AbstractNeal.pdf

The caldera after the 2008 eruption, with the main sites labeled. The new tuff cone has an 800-m crater at the summit. Source: http://www.alaskageology.org/documents/0809/AGSJanuary08AbstractNeal.pdf

The Okmok eruption was detected 35 minutes later, but only in hindsight. At the time, the watchers did not realize what they were hearing. They were in Dunedin, New Zealand, and hadn’t been looking for volcanic eruptions half a world away. The volcano’s calling went unanswered.

Sferics and whistlers

Sferics and whistlers, from Palmer Station,  Antarctica. Sferics are the vertical lines; curved ones are whistlers. Source: wikipedia, Stanford VLF group.

Sferics and whistlers, from Palmer Station, Antarctica. Sferics are the vertical lines; curved ones are whistlers. Source: wikipedia, Stanford VLF group.

During the first world war, an inventive German physicist, Heinrich Barkhausen, used a system of tubes and wires to pick up radiation leaking from nearby phone lines. In 1911, Barkhausen had become the first professor in the world in electrical engineering. During the war, he was close to the front, and the phone lines he was spying on were on the other side. But apart from intercepted calls home, he discovered a very different kind of signal. Every now and then, a strange, fast descending tone came from his system. The Germans called them ‘whistlers’ because they sounded like the whistling shell being fired at them. Barkhausen could find no good explanation and suggested they were atmospheric.

Whistlers happen at frequencies around 5 kHz, the VLF band (VLF of course stands for Very Low Frequency). They last a few seconds with a descending frequency. in the 1950’s, after many years of studies, they were traced to lightning activity, confirming Barkhausen’s opinion. The reason that this took so long is that the lightning which caused it was not particularly nearby. Quite the opposite: it could be as far as 15,000 km away! Not quite antipodal, but not far off. What happened?

From www.wunderground.com

From www.wunderground.com

Lightning is caused by electric charges building up in clouds. Ice crystals in the cloud become charged by friction. Small crystals are positively charged and large hail stones acquire negative charge. Hail stones tend to fall downward, but the small crystals are blown upward. This gives a tremendous charge separation, with the top of the cloud positively charged and the bottom layer negative. Below this, the ground becomes positively charged. The charge difference finally exceeds the insulating capacity of air. A spark begins to fly from one end. The heat of the spark ionises the air and suddenly the air forms a conducting tube. Once the spark reaches the opposite charge (often trying out various paths until one works), an instantaneous current flows, typically around 10-100 kilo-Amp. The lightning flashes, and the over-heated air causes a sonic boom. Cloud-to-cloud lightning is called a lightning flash, and cloud-to-ground a lightning strike, but there is no fundamental difference between them; note that you can’t get strikes from the top of the cloud directly to the ground through the bottom cloud layer as they have the same charge. (A third type is cloud-to-space, traveling upward. These are called sprites and elves, common but difficult to spot.) Lightning blinds and thunder deafens: people lose their two most important senses simultaneously. The sound can be felt as a disorientating pressure wave. The smell of ozone completes the quartet. It is a frightening experience. Being hit is even worse, of course, and involves a significant fatality risk as the current interferes with the heart and can stop it. A nearby strike can have the same effect: the current travels through the ground especially when it is wet (not uncommon during thunderstorms) until it reaches your feet, and if those feet are some distance apart, it causes a voltage difference between them. A current flows through your body. After a personal experience with a particularly bad thunderstorm, I now know that cattle are particularly prone to this: their legs are very far apart so they attract a lot of current – a bug in their design.

Source:  Weather underground

Source: Weather underground

The instantaneous current flowing through the lightning path causes an electromagnetic pulse to travel outward in all directions. Our bodies are not equipped to detect this radio wave, but it travels the furthest of all lightning signals. Whilst light is limited by the horizon and thunder sound waves curve away from the earth’s surface and can’t be heard more than some kilometers away, the low-frequency radio pulse can curve around the Earth, by continuous reflection between the ground and the ionosphere. In this way it can reach up to 2000 km before fading below detectability. At that distance, there is no indication of any thunderstorm: literally a bolt from the blue.

The radio emission, called sferics (for radio atmospheric signal), is strongest in the VLF band. They have broadband frequencies of around 10-100 kHz and wavelengths of 3-30 km. Modern lightning detectors use these sferics. They use a network of sensors over a region, and from the difference in arrival times at each sensor can calculate where the lightning occured. Four sensors are needed for an accurate position but in practice five are used. Detection rates vary, but for the world-wide network typically 15-30% of detected lightning strikes can be located, mostly for lightning currents in excess of 30 kA. A denser grid of sensors helps, and therefore national networks can perform better and also detect weaker lightning.

But if the wave can travel upward and reach the ionosphere, 100 km above the Earth, it can travel along the magnetic field lines – and these bend around the horizon to the other hemisphere. The lines connect pole to pole, and initially go out, reaching high altitudes over the equator. Across the equator they begin to curve down again. Finally, they enter the Earth’s surface on the way to the centre. The point where a field line leaves the Earth’s surface and where it re-enters will be at the same distance from the magnetic pole (but the opposite pole, obviously). The point of re-entry is called the conjugate of the outward crossing. Because of symmetry, the outward crossing point is itself the conjugate of the re-entry point: each point has a unique magnetic conjugate.


Thus, the electromagnetic wave which reaches the ionosphere will eventually approach the conjugate point of its origin. Here a fraction of the wave leaks through to the surface, and interferes with the radio enthusiast. The higher frequency travel faster, and thus the
interference begins at the highest frequency and descends as the lower frequency parts of the wave arrive. Thus the whistler is born. When you are hearing a whistler, it is your magnetic conjugate calling, from a world away. Listen carefully.

Listen carefully

In practice the waves can first travel across the Earth’s surface before finding their way into the ionosphere. Thus, when you hear whistler, it may be from lightning not at your conjugate point, but some distance from it. The real location of the lightning could be as far as 2000 km from the point you are listening to. This is what makes research frustrating – and exciting.

There are many VLF receivers around the world which detect sferics and whistlers. The signals are automatically analyzed, by what is called an Automatic Whistler Detector and Analyzer, or AWDA for short. (This slightly disappointing acronym seems open for improvement. How about Analyzing Detections of Whistlers by Automatons!, or AnD WhAt!.) This has shown that Hungarian whistlers come from the East coast of South Africa. Whistlers at the Antarctic Peninsula come from the Gulf Stream. But in both cases, there are also correlations with other regions with high lightning activity, closer to the equator. Apparently equatorial lightning has a separate path, not via the conjugate point, to travel long distances but the details of this are not understood. Lightning is much more frequent in tropical climates, and even a minor leakage here can become noticeable.

Dunedin and the Okmok whistlers

Dunedin in New Zealand is geographically opposite (antipodal) to Coruna, Spain, a cultural highlight. But its magnetic conjugate is not there. The local magnetic field line connects to 55.84°N 174.70°W, just north of the Aleutian Islands. This should make Dunedin a good place to avoid whistlers, as lightning is fairly rare in the Aleutians. Still, whistlers are heard. After detailed studies, the conclusion was reached that the Dunedin whistlers are best correlated with lightning activity at the west coast of Central and North America. The lightning rates here are 2000 times higher that those in the Aleutian Islands, and so even if only a small fraction makes it to Dunedin, they will still dominate the numbers. But the area is 6000 km from the conjugate point. Apparently an alternative path exists which allows the waves at this location to travel below the ionosphere towards Dunedin. The details of this connection are not clear. Getting to New Zealand can involve mysterious ways.


On 12/13 July 2008, an enormous number of 21,021 whistlers were detected at Dunedin. They started suddenly and ceased after nine hours. This was one of the highest number of whistlers ever recorded here: usual numbers are less than 1000 per day. Over an 8 year period there were only two days with a higher count (both in the second half of 2012). Even stranger, the spike happened during daylight hours when whistlers don’t travel well. The spike was noticed at the time (it was hard to miss!) but the cause was not known. There was no thunderstorm activity in the usual suspect region of North/Central America. The answer was only found six years later when people looked for activity near the conjugate point. It was the volcano radio of Mount Okmok.

Mount Okmok is located 350 km from Dunedin’s conjugate point. Two other rather active volcanoes are also within range of Dunedin’s magnetic conjugate: Mount Redoubt is 870 km away, and Mount Kasatoch 815 km. But the clear culprit was Okmok and its significant eruption that day.

Mount Redoubt: another radio-active volcano

Mount Redoubt: another radio-active volcano

Two other possible cases of volcano radio were however found in the Dunedin records, related to these two. Mount Redoubt had several eruptions during 2009, and its eruption from 26 to 28 March coincided with a high count of whistlers. Other Redoubt eruptions did not lead to higher whistler counts.

Mount Kasatochi (Kasatochi Island) erupted on 7 August 2008. The 14 km ash cloud led to 36 whistlers. An eruption a few hours later did not add to the whistler count. So both Redoubt and Kasatochi are radio-active – but Okmok far outstripped them.

Volcano lightning

The clear cause of the whistlers was lightning activity in the ash clouds. The eruptions that showed whistlers had lightning – the others didn’t. The World Wide Lightning Location Network (WWLLN – I would have gone for the acronym www.lightning.net) showed that lightning at Okmok began 35 minutes after the onset of the eruption, mostly within 10 km of the volcano. The Dunedin whistlers began at the same time. WWLDN measures the time of a lightning strike to 30 micro-seconds (although it tends to see only the strong strikes), allowing individual whistlers to assigned a particular lightning strike.

he May 2008 eruption of Chaitin, Chile,  showed plenty of volcanic lightning. Photo by C. Gutterriez

The May 2008 eruption of Chaitin, Chile, showed plenty of volcanic lightning. Photo by C. Gutterriez

We have many images of volcanic lightning in explosive ash clouds. But how does volcanic ash generate lightning? How does it build up the electric charge and how and how does it discharge the charge? Part of this is not difficult to answer. Even in normal thunderstorms, adding a bit of dust to the atmosphere greatly increases the lightning activity. Saharan sand over Europe can coincide with very impressive thunderstorms. Part of this may be due to the sand itself being charged, in the same way as the ice, by friction. But dust grains can also act as condensation nuclei: adding a bit of dirt to air makes it much easier for the water to condense.

Volcanic ash is not the same as sand. Does it work the same way? Or is the crucial difference the water mixed in with the ash? Wet eruptions are more ashy, so the two often go together. Recent studies of Sakurajima have shown that the volcanic lightning occurs in the lower parts of the ash plumes, relatively close to the ground. The electric charge apparently is already created in the initial explosion. This is different from thunderstorms where it is created at higher altitude.

Video of Sakurajima’s lightning

It is a strange thought that VLF radio can be used to detect -and locate- distant eruptions. Mount Okmok was first heard 11,000 km away, across the entire Pacific. If the Falklands (or Malvinas, depending on your preference) erupts, England could be the first to know, via radio whistling. (The lack of a volcano on the Falklands may make this scenario less likely, of course.) But of course the whistlers really detect the lightning, and lightning can also be detected directly. If you monitor the WWWLLN you could already know about the eruption. Whistlers are more sensitive: the WWWLLN detects only a fraction of the strongest strikes, and you can detect whistlers from lightning missed by the WWWLLN. But the whistlers also tell you other things. With volcanic whistlers, you know exactly where the lightning occured, and therefore how the radio wave traveled. This tells you how well the lightning connects to the ionosphere – and that is a poorly understood problem which may also tell us a lot about volcanic ash in the stratosphere. Scientists have found themselves a new tool – what they will eventually use it for can be hard to predict. Who could have expected that Heinrich Barkhausen’s early experiment in government snooping would lead to real-time monitoring of thunderstorms and volcanoes on the other side of the world?

Hidden love

And the title of this post? Lightning Of Volcanic Eruptions uses whistlers to send messages from secretive and hidden volcanoes around the world to their conjugate admirers. Volcanoholics need more LOVE.

Based on the article: Investigating Dunedin whistlers using volcanic lightning, by Claire Antel and collaborators. Geophysical Research Letters, Volume 41, Pages 4420–4426 (2014)

52 thoughts on “Volcano Radio: From Okmok with Love

  1. The most powerfull lightning strikes are actually positively charged, so called CG+ strikes can carry a lot more energy then regular cloud to ground lightning. They usually form from the positively charged anvil part of a thunder storm

      • Interesting! These go around the bottom of the cloud so avoid the negative lower reaches. Rare though.

        • And bloody scary seeing where and how they strike, most people will remember lightning strikes that came from nowhere and sounded like an explosion. The chance of these being CG+ are pretty high.

          I can remember a dissipating lightning storm a few years back that wasn’t much more then a left over anvil slowly raining out, however it did still manage to produce the odd strike. One of these struck a big poplar tree about 1.5km away, the damn ding pretty much disintegrated the tree and sounded like a small nuke going off..

          • Yes, in principle the spark can fly from either direction. It normally starts in the cloud where the field is strongest, but in this video the tips of masts act as the starting point. Of course the fields at a narrow tip can also get very strong, and this is not surprising. It would be surprising to see it go up from the ground.

          • For it to be emanating from ground level the field would have to be enormous, as far as I know streamers always start from high(er) points not matter which way the strike eventually ends up going.

            Another intriguing lightning related reading subject is the terrestial gamma ray flash, sometimes it seems the more we detect the less we understand.

          • Yeah, but as Albert pointed out it will always start from a point higher up, that being some sort of tower, (very) high tree or other elevated object where the charge has the oppurtinity of concentrating.

            Somewhat related to the disproven point of lightning always hitting the highest point I guess?

            My guess is that it’s a lot harder for the “stable” earth surface to build up the required charge for a ground to cloud strike then it is for a proper dynamic lightning storm to generate the charge to do the opposite

          • I saw one this summer coming up from a rape seed field.
            I was standing under a road tunnel looking out. The field was very strong, I could actually feel the field across my skin for a minute before it went up.
            If I had any hair at all I guess it would have been dancing about, but since I do not I had to go by the skin feeling. It was like thousands of tiny tiny needles pricking me all over.

          • I would guess that what you saw was the return flash, but that the original spark came from above. Your description of feeling the hair on your skin sounds like the tendrils os the lightning sparks were getting close. Once one of them reaches the ground, you get the flash traveling along the path. It could have been you..

  2. Albert this is awesome information! I did not know anything about this at all – and I love learning new stuff all the time. Thank you very much for such an intriguing article!

  3. Awesome article Albert!
    And you have just explained something about bankers I have always wondered about 😉

    • I am still chuckling at the jokes and puns that Albert put in. This article gave me bad ideas and a warm fuzzy feeling inside as all good science should do.
      When Albert started talking about this article I was highly intrigued and boy did Albert deliver. This is my absolute favorite so far!

  4. Really interesting article, though I suspect I’ll have to reread it a few times to understand everything, the subject matter is a bit above my head.

    There are however an annoyingly high number of typos in the article (or the few that are, just really stuck out to me)

    • The horribilities with an international site where most of the writers are not native UKians. 🙂

    • Typos are fixed when I find them. There isn’t always enough time in a day to finish the polishing! Science can have rough edges.

      • Repeat due new post, from Kaikoura…

        Hi XXXX
        Remember you both well, I am pleased to report that we are ok in fact I wrote a bit of a blurb to send to
        Our friends and guests so will add it below, and yes you are right the sea is definitely lower than it was but not to the extent that it is further up the coast.
        An extremely unpleasant experience and would not like to have it repeated and luckily we rose up with the rocks at the same time so it could have been worse if that fault line had torn through  the main part of town and South Bay. At present the aftershocks have settled so we are keeping fingers crossed that the worse is over however also know that we could have more over the next year.

        Our little home business is stuffed for the year as is most of the town so it is very quiet, one or two cafes up and running so the locals who can seem to meet there for a morning coffee, and it is helping to keep us in contact and in good spirits, still a lot of army trucks and civil defence folk around and scientists and geologists about as this has proved to be the worse quake in NZ history and the movement of the land and sea and the fact that several separate faults erupted at the same time at a rate of 3 km a second I think I heard on the radio, is something they wish to study.

        A heap of campervans and rental cars parked up at our racecourse awaiting to be driven out when we finally get some roads open, but that could still take a few weeks hopefully we will get down to Christchurch for our annual Christmas dinner with family but not counting on it, even the small aircraft are fully booked so we will just have to hang in there.
        Great to hear from you again xx
        Regards to you both

        thank you so much for your email, pleased to report that we are ok, sorry for such a delay in getting in touch, had to deal with many cancellations and family phone calls etc. and were without phone email etc for first week, we have had no damage to the house or property, thank goodness for that hard limestone rock under us i think. it was an awful night and very frightening and we spent it up on the peninsula hill with the rest of the town and all the poor tourists that were caught up in this.
        spent the following night in the car as well, as many after shocks kept us on our toes.

        anyway we have all the services back on, limited showers and water usage and that is wonderful after not having any for 10 days or so, it is amazing how much we waste and have had a good reminder of that!
        town has taken a major economic hit and it will difficult for some businesses to survive this, we were all set up for a bumper tourist season and that of course is the problem as no access by road yet, some limited access today for a week or so but the contractors have to repair it as well so we are expecting that we will be stuck here for several weeks yet. the farmers are having to dump milk and have problems with dairy sheds being written off and trying to get water to stock, just today there was a photo on the internet of a lamb which was stuck in a large crack in the ground where the fault line errupted. poor little thing had been stuck all this time but had survived.

        we now have been uplifted one metre up, which means that we have a new low tide line and more rocks are exposed out in front of the house it also means that sea rise due to global warming will give us another 50 years!!  so guess that is one advantage.
        the land has risen a massive 4-6 metres to the north of us and the road and rail lines are completely stuffed so we will be without a main highway to Blenheim for at least a year so they say, and the road  route possibly will be altered permanently, to the south, well that has been badly damaged but we are hoping that may open before christmas, the only way out is via the inland route but that is causing major problems and is also the only way to get supplies via the army in.

         Pleased to report that sea life all ok baby seals ok and at present a ban on crayfishing and paua as those stocks were affected by the seabed uplift.
        The whale watch and dolphin boats are stuck in the marina as the tide line is now to low for them to get out and marina is going to be dredged and rock removed asap so that if the road opens then folk can at least have that experience when here. Of course the main issue for a lot of businessess is the fact that
        what was once a main thru fare is now not, so dont have the through traffic wanting coffee and food etc. all in all a bit of a disaster.

        a number of homes and business are written off and we had two fatalities, however the support of people such as yourselves has been truly overwhelming and we could not have been luckier.
        at least the tourists could be flown out within a few days and we have several carparks all over town with even the racecourse acting as a park for abandoned campers and cars so there is still a massive disruption to the town and rest of south island as accommodation is altered and vehicles booked cannot be returned.
        our air field will be extended and better roading etc will benefit from all this, so in the long run at least something good will prevail and one towns fall will give rise to anothers boom, and as a bonus we dont have those big trucks on the road for the next year!

        Thanks again for all the care and kind thoughts, we intend to hang in there unless we get an offer we cannot refuse!!! and are in good spirits,
        last day of spring today and we are having a little rain, good for the garden at least as have been unable to water it.
        stay well and our love and regards

        • Thanks for sharing! Always interesting to read first hand accounts and to illustrate how such events impact the communities and environment in the area.

        • Better news on possibility of reopening the road to the South:

          Earthquake-hit sections of State Highway 1 south of Kaikoura are set to reopen within weeks, after faster than expected progress.

          Transport Minister Simon Bridges said work to clear slips on the southern section of State Highway 1 following last month’s magnitude-7.8 earthquake had exceeded expectations.

          “We are making much better progress than expected at this point in the recovery and as a result it is anticipated the road will be opened much sooner.”

      • Great article, Albert.
        This is not a typo, but a small mistake. In the last paragraph, you talk about Falklands… but its spanish name is “Malvinas”, not “Maldivas”, which are in the Indian Ocean

        • Thanks! Fixed. Trying to be culturally inclusive is not much use if you get the name wrong..

      • Right next to the image of Mount Redoubt there’s this one “An eruption a few hours later did not ass to the whistler count.”

        I guess when you (me) don’t understand the subject fully, the mind get’s diverted by errors and such and makes it out to be a big deal.

        • Any corrections are gratefully received. This is actually part of the process scientific papers go through. They are read carefully by a number of people, co-authors and referees who find mistakes and/or suggests corrections, before a paper finally can appear. Much of the difference in the ‘good’ and ‘bad’ journals come from how rigorous this process is. For this blog, sometimes this happens in the back channel. but not for this one. Stef found a mistake in whether lightning from the top of the cloud level to the ground is possible. That is good input into the discussions here.

    • I suppose they’ll not be taking any chances after Calbuco surprised them!

      • For sure. In some level of fairness, Hudson is very well monitored, but it also has a history of going boom in very large ways.

        It had two VEI-6 eruptions in the Holocene separated by roughly 3000 years. In 1991, a little less than 4000 years after the last VEI-6 eruption, it had a VEI-5 eruption which was one of the largest in the last 30 years. In 2011, there was a small throat clearing eruption that created a series of new craters.

        Normally, I would assume that it would still be rebuilding from the previous VEI-5 eruption in 1991 similar to St. Helens. But we should keep in mind that this is a volcano that has had at least two VEI-6 eruptions that were way larger than the VEI-5 eruption it had, and has had more time since the last vei-6 than it had between the two previous VEI-6 blasts.

        I wouldn’t call it likely, but we shouldn’t rule out the fact that the VEI-5 blast could be a prelude to a larger eruption here. I would estimate that the magma chamber is quite large here (large enough at least for a VEI-6) and a VEI-5 eruption will do a lot to deplete it, but there still may be a LOT of potentially eruptible magma down there ready to go.

        • And of course we know about plenty of examples where this situation has occurred. St. Helens had two VEI-5 blasts in 3 years (7.7km3 and 1.5km3, almost a “staggered” VEI-6), and when it reactivated after a 6000 year dormancy it had a big VEI-5 followed a century later by a Pinatubo-sized VEI-6, its biggest ever eruption by far. The Crater Lake VEI-7 was preceded 200 years earlier by a borderline VEI-6. On a magnitude smaller, but the amount of VEI-4 blasts at Kelut in the last century is staggering. Even the Long Valley VEI-8 was preceded relatively closely by a VEI-7. Whether a 20 year gap is too small, who knows?

          • There’s six layers of ash from a little-studied volcano in Alaska known as Hayes Volcano (NOT to be confused with Mt. Hayes further north in that same state!!!), with an average volume of 2.4 cu. km (Mount St. Helens’ May 18, 1980 eruption =1 cu. km) from about 3400-3800 years BP, a period of roughly 400 years. That’s a VEI 5/6 eruption every 67 years on average!

            This volcano is about 142 km (88 mi) NW of Anchorage, so it’s further north than Spurr, but still not much farther from Anchorage. It wasn’t even discovered until 1975, probably because of its remote location and being so heavily covered in ice with no clearly volcanic features and no fumarolic activity visible.

    • I feel a bit sorry for this one:

      Seems to be a candidate for frostbite, has a look of concern – the balloon just popped and it’s a long way down.

    • I think it’s appropriate to provide some background info, since no credits were given.
      Earth to Sky Calculus is a group of high school students in California (with new groups forming elsewhere) that have been conducting experiments/monitoring of the upper reaches of the atmosphere. With the guidance and support of Dr. Tony Phillips at http://www.Spaceweather.com, these young men and women have been sending balloons with instruments to the edge of space to measure the local conditions including cosmic rays, as well as testing how organic items such as seeds, etc. can be affected by cosmic rays plus the other hazards of high altitude exposure. They have also sent their detectors on airplanes to measure how much radiation pilots/passengers get exposed to during high altitude flights. A particularly interesting outtake from the monitoring seems to be confirming that during periods of solar quiescence (low solar wind), cosmic rays striking Earth increases, since the flux of the solar wind acts as an electrostatic barrier that deflects the cosmic rays away from Earth.
      Since ETSC is totally non-profit, and they fund their experiments through donations (I am one) and promotions (such as the pickle), I would encourage all to check out their data and applaud their efforts appropriately….maybe even drop a few bucks into the till?
      IMHO, this is what “education” in today’s world should be….where all things are open to question and debate, solid/thorough thinking is nurtured and then theories tested….and in return our businesses gain a more highly skilled (and innovative) workforce from within, instead of having to seek better qualified people from elsewhere in the world.
      Unfortunately, here in the U.S. the educational powers-that-be do not see it this way, and are more determined to create legions of “indoctrinated” minions in lock step with those who thrive on an obedient and educationally deficient populace that can be better exploited for maintaining political power and personal/corporate gain.

      • Note: I purposely ommited getting into the potential societal impacts of an open vs. closed educational paradigm, since I’ve probably gone too far with my brief rant as it is…and it really is all about the pickles, right?

      • Sorry Lurk, I did not notice your post with the ETSC link (credit). I just saw Oruanui’s other pickle picture and ran with it. Sure wish this blog had edit capabilities!

        • Not a prob. It gives a good endeavor more coverage. My lack of commentary was more from the shock aspect of people discovering stuff on their own. It falls into that “Owner of the process” thing from Total Quality Management.

          Anytime you can keep kids interested in science, you get a more productive person in the long run.

          • After spending 34 yrs. in the Semiconductor equipment field, how I know all about TQM and ownership. What I eventually specialized in was devising new and innovative tests and metrics to increase equipment performance and yields…oftentimes challenging existing paradigms and systemic inconsistencies in the process….i.e. the pursuit of Continuous Improvement through data and experiment.
            But that was only half the battle. The other half involved trying to “sell” the data to the stodgy higher-ups in order to implement positive change. It was amazing how often definitive data went unacted on….and one of the reasons I got fed up with the whole mess and decided to go off on my own. Ahhh, politics…always the politics.

  5. So after Mike’s comment, I ended up doing a few searches, and found something tangentially related to the Aleutians which is really interesting, and related to tsunamis.


    Some people on here know that Aniakchak was a very large eruption around the same time as Santorini. It is listed as a VEI-6 eruption, but this is innacurate. I had never known however that there were distal tsunami deposits from this eruption, upwards of 15 meters high. The interesting thing about this is that Aniakchak is not located directly on the water like Krakataua, and it did not have a flank collapse that slid into the ocean. The tsunami was created from nothing more than pyroclastic flows that hit the ocean more than 30 kilometers from the source of the actual eruption.

    I hadn’t even realized this was a possibility, at least for a VEI-7 sized eruption.

    • Also happened in Tambora: that caused tsunamis by pyroclastic flows reaching the ocean. The earlier tsunamis of Krakatoa were probably pyroclastic: only the last, strongest one would have come from the collapse of the island. The report you link to says it is a bay. Bays can amplify incoming waves, and that could explain the large height. Note that is can be difficult to distinguish storm tides from tsunami tides just based on the debris.

      • I hadn’t realized this happened at Tambora. I would have to imagine that this is somewhat important to know in terms of mitigation.

        If any volcano were to have a large eruption somewhat close to water, I would hope that people would know that they should expect a potential tsunami.

  6. Great. The ol’ “Finger of Thor” treatment. So, “BOOM” goes the mountain, you are too close, and lightning strikes you dead where you stand just prior to the pyroclastic flow overtaking, incinerating, & burying you out of spite.

    That is terminal AND acute cardio-respiratory failure with a nice side complication of 100% 3rd degree burns, blunt force trauma, and crush syndrome all in one!

    • Pretty much sums it up. While someone half a world away listens to the whistler announcing your demise. Life and death of the volcanoholic.

  7. Somewhat random, but just found a new good candidate for a future VEI-7 at Recheschnoi in the Aleutian arc. Given, you can do this for a lot of volcanoes, especially in the Aleutians, but it’s still interesting at the very least. More or less, it checks a lot of boxes, which is always a fun exercise.


    -Has lots of rhyolitic products.
    -Extremely active geothermal field implies high heat production and currently active status.
    -Long repose time indicates future activity may be quite large.
    -Location next to another VEI-7 eruptive caldera (Okmok) could indicate that it could suffer a similar fate.
    -The presence of pyroclastic cones on the flanks *could* be indicative that the central conduit is fully blocked, and magma has started to look for other paths to depressurize (although this isn’t that much of a factor).

  8. Pingback: The Bogoslof eruption | VolcanoCafe

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