The Un-Frozen North – A Hotbed for Large Volcanic Activity

Guest post for VolcanoCafé by Greg S (Aka Cbus05)

One thing I have come to realize after years of reading about and following volcanoes, is that there is a considerable bias in people’s interest towards certain volcanoes. I used to think there was a western bias, but this phenomenon is just as prevalent in Japan and Indonesia, with many articles written in their native tongue about famous volcanoes such as Fuji or Merapi.

Mt. Fuji

Mt. Fuji is an extremely well-known volcano, partially owed to its beauty

Realistically, the bias is more such that volcanic regions that are extremely remote get very little attention. This is understandable, why should people worry about or care about volcanoes that are way far away from civilization? It also makes more sense that funding and monitoring goes towards volcanoes that have a higher likelihood of impacting people, so some of these remote regions simply do not get as much love as they potentially deserve.

While I don’t blame the average person for not spending lots of time understanding distant volcanic arcs that probably will never affect them, I have found an extremely valid reason why those of us who are more volcanically inclined should pay a bit more attention to these remote regions.

I will get back to that reason further down this post.

Caldera Eruption Findings

Over the past 12,000 years, the period referred to as the Holocene, there have been a variety of very large volcanic eruptions and volcanic events that have been well-studied. On the VEI-scale, there have been no VEI-8 sized eruptions, but there have been a few VEI-7 sized eruptions, similar to Tambora’s blast in 1813 AD.

According to the Global Volcanism Program, there are 9 listed and verified VEI-7 eruptions, coming from the following Volcanoes:

  • Tambora – 1813 AD
  • Rinjani / Samalas – 1257 AD
  • Changbaishan / Baekdu – 969 AD
  • Taupo – 230 AD
  • Santorini – 1610 BC
  • Cerro Blanco – 2300 BC
  • Kikai – 4350 BC
  • Mt. Mazama / Crater Lake – 5677 BC
  • Kurile Lake – 6440 BC

My Personal Research Into Caldera Eruptions

On my own blog;, I wrote a post that goes into detail on a different way to track large eruptions. In that post, I listed the largest volcanic eruptions of the Holocene period based on the size of the calderas being formed.

My reasoning for doing this was the fact that large eruptions are likely highly under-represented in the current record. My simple reasoning is that caldera size has a direct relationship with eruption size, and there are many large calderas out there that formed in the Holocene that we haven’t really accounted for.

Luckily, we have some good measuring sticks – those being the well-measured and researched VEI-7 eruptions of the last 1200 years (Tambora, Changbaishan, Samalas/Rinjani). We know with much greater accuracy how much ash was ejected at these volcanoes, and we can also accurately measure the size of their respective calderas.

As a result, it’s fairly reasonable to assume that volcanoes that created a caldera of similar or larger size likely came from eruptions that were of a similar size or larger. There are some important caveats here, and this is not by any means a perfect system, but it DOES give us a much more accurate ballpark to determine how many very large eruptions have occurred during the Holocene.

What I Found was Quite Interesting

By scouring every source I could to find known dates of large caldera formation, I was able to round up a pretty sizable list – significantly larger than the current list of 9 volcanoes that have gone VEI-7 in the Holocene. The list currently sits at 27 volcanoes that have created Tambora sized calderas or larger, with a few additional volcanoes that are more uncertain.

This dramatically changes current expectations of caldera eruption frequency for VEI-7 range events.

It has previously been thought that VEI-7 eruptions occurred approximately once per 1000 years as a very rough estimate. This is wrong.

With 27 known large caldera eruptions over the last 12,000 years, this provides an approximation of a large caldera forming eruption every 444 years (note that I won’t say VEI-7 since that can’t be verified). If you account for the fact that there are likely quite a few large eruptions that have not been discovered or dated, we would see this interval fall down into the 300’s, which is way more frequent than many would have thought.

Back to Volcanic Regions…

When compiling this list, something basic stood out to me like a sore thumb. There were three regions that accounted for over half of the total volcanic eruptions (15 total).

The most notable region was the Aleutian Arc in remote Alaska, which had 6 known large caldera eruption events during this time period, and also had numerous nested caldera events or smaller caldera eruptions (like Katmai).

Second most active in terms of large caldera creation came the remote island of New Britain (and islands north of New Guinea) with 5 events, although we know considerably less about the eruptions here. This is particularly impressive given the fact that this is not a particularly large volcanic arc. No region has had a higher rate of caldera formation per volcano than New Britain has.

Third Most Active is Kamchatka and the Ryukyu Island Arc with 4 caldera eruptions. Including the Ryukyu arc may be cheating to an extent however, since it could just as well be claimed by Japan. Either way, Kamchatka has had numerous other smaller or nested caldera events as well, and has been the most active region in the world for caldera formations over a longer period of time than just the Holocene.

The Unfrozen North

When you consider the fact that Alaska and Kamchatka are right next to each other, it becomes even more interesting that there were so many large caldera eruptions that came from remote regions close to the northern pacific.

Aniakchak Caldera

Aniakchak Caldera, one of the many Aleutian Caldera Volcanoes

Alaska Caldera Formations in the Holocene Period

Aniakchak: Aniakchak’s 10×10 caldera formed during a major eruption 3400 years ago according to the GVP. Pyroclastic flows from this eruption travelled over 50km to reach the Pacific ocean, where they were large enough to cause a significant tsunami. Aniakchak has also been highly active even after its major blast, with many other sizable eruptions that have occurred since.

Veniaminof:  8 x 11 km, glacier-filled caldera that formed around 3700 years back. The detail in the GVP isn’t quite as high on the caldera eruption here, although there is likely other literature that can be found on this volcano.

Fisher: 11 x 18 km, the Fisher Caldera is possibly the largest caldera that has been created in the last 12,000 years. Kikai is technically bigger, but that’s only because it is a nested caldera, whereas Fisher formed in one fell swoop around 9400 years ago. It has been researched and most studies state that it was a VEI-6 eruption based on measurements of the eruptive products, but I’m not buying that. Pinatubo-sized eruptions don’t create Long-Valley sized calderas.

Okmok: 10 x 10, Okmok is a monster in another way – it created a 10 x 10 caldera not once, but twice in the Holocene, once at the very start of the Holocene, and a second time at approximately 2050 years back. If we were to count each individual caldera formation here separately, there would be 7 large caldera formations in the Aleutians, and not 6.

Seguam: With a size not entirely known (I estimate around 6×7 based on measurements), Seguam has two calderas, but there is one particularly notable caldera that seems to be larger than what it’s listed as (going off measurements made using Google Earth). This caldera is probably more of a collapse scarp, where we don’t truly know how long it goes as the scarp heads into the ocean.

Semisopnochoi: This is a very little-studied caldera far out in the western Aleutian islands that is 8km wide. It is thought to have formed in the Holocene period.

Why Are the Aleutians so Active During this Period?

While I won’t say anything definitive, there is one fairly obvious answer – that being of deglaciation. Just like Iceland saw an increase in large effusive eruptions after glaciers went away, it’s not surprising that the northernmost subduction arc in the world also had a period of greatly increased volcanic activity after the glaciers retreated.

How long will the effects of deglaciation affect volcanoes? That’s tough to say, but considering we were still seeing big caldera eruptions as recent as 2000 years ago, and have seen smaller VEI-6 caldera events such as the eruption of Novarupta, it’s likely that heightened Aleutian activity is not yet over.

Last glacial vegetation map

In this map, Gray represents glaciers during the last ice age (Wisconsin Ice age). If you look closely, you can see where the ice sheets extended across where the Aleutian volcanic arc currently sits.

Were these eruptions VEI-7 in size? Why aren’t they listed in the GVP as such?

First off, not all of these volcanoes have been extensively studied. It takes a lot of money to undergo an expedition to a remote island volcano in the frozen north. Furthermore, it’s necessary for scientists to justify the reasoning for that study, so we don’t see nearly as much research on these types of volcanoes as we do on volcanoes such as Mt. Shasta, or Vesuvius for example.

For the volcanoes that DO have a lot of research performed on their eruptive history, the Aleutians are particularly challenging when it comes to measuring eruptive deposits. Not only do they sit in a region where there was likely rapid weathering and lots of glacial activity, they also are surrounded by the ocean, which is quite effective at hiding eruption deposits.

As such, it would make sense that some eruptive output estimates are extremely conservative, or simply far off base due to the erosion of those eruptive deposits. That’s not to say all of these eruptions definitively created VEI-7 sized eruptions, but we should at least realize that these are NOT small calderas. All of these are larger than Tambora, some of which dwarf Tambora’s caldera, which we recognize as a definitely large eruption which affected the world.

Summarizing Things…

Well, this was an exceptionally long-winded post that basically states that the Aleutians are the most active volcanic arc in the Holocene, and the most likely to produce a large caldera forming eruption.

We don’t pay much attention to the Aleutians because they are out of sight and out of mind, but another large eruption would certainly have some ramifications that would affect people far outside the Aleutians.

Greg S (Aka Cbus05)

85 thoughts on “The Un-Frozen North – A Hotbed for Large Volcanic Activity

  1. Thanks for the article Greg! I agree there is a lot yet to be understood and poster child volcanoes tend to attract the most monitoring and research for the reasons you highlight.

    Where will the next big one come from? We often say it’ll come from somewhere unexpected and understudied 🙂

    And so I wonder whether there is a distinction to make between explosive Caldera eruptions and those formed by other processes, such as subsidence. I’m not sure what the question is here, I can’t quite frame it in my mind, but does one have more of an affect than the other? I guess it’s all in the gases …

    Anywho, happy Friday all!

  2. I have some data to share:

    Changbaishan 942AD – 75km3 (calculated from 30km3 DRE value)

    Aleutians/Alaska Peninsula:

    Fisher 8100BC – 100km3
    Semisopochnoi 7925BC – 120km3 (largest ever known eruption in Alaska)
    Okmok 7275BC – 50km3
    Veniaminof 2115BC – 100km3
    Aniakchak 1628BC – 100km3
    Okmok 75BC – 50km3

    • One of the challenges seems to be whether we are analyzing bulk volume or DRE.

      Some of these, I’m highly skeptical on the measured size. I’ve read papers that mention isopachs and such for a lot of these eruptions, but some things just don’t make sense. In a general sense, I expect volcanoes to follow the laws of physics in the most basic manner. The most glaring error to me seems to be coming from Fisher Caldera.

      As a very rough estimate, the 11×18 km Fisher Caldera probably has a volume of over 120 cubic km (and that’s extremely conservative).

      IF we’re assuming the output was 100km3, then how do we explain the size of the caldera being larger than the amount of material displaced from the magma chamber during the eruption? There is just no way that the volume of a collapse caldera is larger than the volume of the material displaced. This would imply that the material emitted somehow compressed AFTER they were erupted, which makes zero sense.

      In all our more recent and well-studied examples of caldera collapse, we know that the amount of tephra deposited during the eruption tends to be a lot larger than the net volume of the collapsed caldera. Tambora for example deposited around 150 km3 of material. The caldera size there is circular 6x6km with a depth of a little over 1km. Assuming a hemisphere type shape, the volume ends up around 55 km3. So in Tambora’s example, a 55 km3 caldera produced nearly 3 times the volume of ejecta.

      Going with another recent and well-studied example, Novarupta emitted around 30km3 of material, creating a caldera roughly 3×4 km in size. This gives us a rough volume estimate of around 12km for the caldera here, which once again, puts the tephra volume at a little short of 3x the size of the caldera.

      You can do this with just about all the recent well-studied volcanoes that experienced caldera collapse, and it holds surprisingly true. The trend holds for Pinatubo, for Rinjani, for Baekdu, and a few others as well.

      • That would just about agree with the basic/general formula of bulk volume= ~2-2.5 x DRE volume (1km3 of tephra for every 0.4km3 DRE). Pinatubo was 11km3 bulk, 5km3 DRE. Mazama was 150km3 bulk, 47km3 DRE.

        Most of the volumes given from the source I found are very general “assumptions” e.g. “somewhere in the low VEI-7 area= lets just say 100km3 bulk, 40km3 DRE”. Some (e.g. Atka) data is just like “we know there was a major eruption, no idea what size, let’s just go with >0.1km3 bulk, >0.04km3 DRE, VEI anywhere between 4 and 7”. The source is like that with a lot of major eruptions of all sizes and all volcanoes it has data for. Even includes several high (0.07-0.09km3) VEI-3 eruptions even though the 0.1km3 mark is the given boundary between minor and major explosive eruptions.

        By the way, I read a (relatively) recent paper that re-calculated the Tambora eruption as ~110km3 bulk and ~33km3 DRE (from other sources this should probably be 37km3 DRE:

  3. If there were a lot of huge eruptions just after the ice retreated, wouldn’t that mean they were the result of that immediate post-glacial rebound?

    I’d think Iceland, when its ice cap finally melts away (sometime this century, yes?) would have the next caldera blast of the North. I’m just thinking out loud.

    Great article though, by the way. You folks should collect all these awesome articles into a book because I’d totally buy it.

    • It’s pretty tough to accurately predict what will or won’t happen. Iceland is more likely to experience large effusive eruptions than explosive caldera collapse, although there are examples of explosive Icelandic volcanism coming after glaciation ended.Those examples include the Saksuvartn eruptions and the Vedde ash eruption. Things definitely do have the potential to get interesting however as more glaciers retreat, especially in Iceland.

    • Iceland recovered very quickly from the ice age, because it was a comparatively small glacier. (It covered all the land, and some 50 km into the sea, but that is still small in ice-age terms.) The rebounce was completed some 9000 year ago already. The remaining glaciers are tiny: melting them will cause havoc in the volcanoes underneath but not affect the rest of iceland. But the next 500 years could be very interesting.

  4. Thank you Greg! I am in the initial stages of writing something of my own, and its quite hard, especially if you are a perfectionist like me. 😀

    So as I usually say, kudos to you!

    • I have the fortune of not being a perfectionist 🙂 . I consider it both a strength and a weakness, just depends on the situation. I feel like a lot of people who work in the sciences tend to be more perfectionistic or detail-oriented people, I don’t think I have the patience for that unfortunately. I applaud those who do.

  5. VON station is back, and it looks like there could be some water flow in the area, perhaps even some hydro-thermal stuff…

  6. Two questions/comments:

    Is it possible that additional calderas are underwater? I’ve always wondered how many eruptions might take place in somewhat shallow parts of the ocean or would underwater mapping have found these?

    Would the climate record point out the larger VI-6/7 eruptions? I guess space debris could count for some of them but generally wouldn’t these be volcanic.

    Good article, thanks.

    • I’ve also wondered about the undersea calderas; the (largely still submarine) arcs between Japan and the Philippines, eg the Marianas, seem to have a fair number of large, apparently youthful calderas which are only vaguely dated, if they’re dated at all

    • Two points: yes, shallow underwater calderas are easy to miss and there may well be some. Lurking pointed out Iwo JIma with a possible caldera surrounding the island (I should say I am not convinced by this one – it seems a wave-eroded plateau to me). Especially island arcs could have some of these below the water line. Deeper calderas not, though. You can’t get explosive eruptions at depth: physics is against it.

      The climate record only has the worst eruptions. VEI7 have possible effect, but VEI6 mostly do not (it depends to some degree on composition and location, not only the VEI). There are a number of posts on this site discussing that. The climate record has been used to show that Eldgja was mis-dated. The missing eruption of 1809 is another one: strong climate effect (it killed off Napoleon’s Rusland invasion), but no smoking gun. That could be a missing VEI7.

      I found about one VEI7 per 300 year or so. That agrees well with what Cbus derived.

      • Some time ago, in a paper that I can’t remember, I read that the water vapor in and around tropical eruptions tends to somewhat mitigate the SO2 plume when a volcano goes off. Aquatic eruptions should be even more depleted of SO2 as the plume has to actually get through a column of liquid water. My guess is that Aquatic eruptions would leave very little signature in the ice record.

  7. I think the risk posed by an Aleutian caldera forming eruption could also pose a very short term risk to life. Considering the routing of commercial aircraft across the region, a major explosive plume (particularly at night) could put tens of aircraft at risk. If you average 300 people per aircraft, then 3000+ people at at immediate risk. Here is a random snapshot taken from Flightradar24 24 tonight.

    • This is definitely true, although the Alaskan volcano observatory should be able to route aircraft around a plume if needed (provided they have the funding for monitoring).

      • I protest such statements. This is scaremonging at best.
        All planes have Radar etc., and and abowe average (intelligent) captains and pilots. And eruptions are monitored for. So far no one has died on large commercial jet whilst several have penetrated plume.

        edited: it violated the ‘be nice to each other’ rule. -admin

        • island’er, I think ‘disgusted’ is a harsh word to use in this context. Eagleowl61 wasn’t scaremongering and was just speculating about a VEI7 eruption on aircraft, something which has never happened in flying history. There’s no harm in debating such events.

          • Speculating in this context is. Just look and analyse this a bit.

            Fact: Most planes on that “snapshot” are NOT overflying the volcanic Arc. How many planes are? I see maximum of three large, one small..

            Fact: Less number of jet fly by night, but there are traffic peaks – usually in morning or afternoon hrs. Daytime.
            Depends on location., but pretty much follows the sun, except North Atlantic eastbound, that fly into the night, but again few active volcans there (except here, and few do VEI7). Just NASA planes fly directly into plumes – they did and damaged (not ruined) engines. Plane is still in service BTW, depite old age DC-8.
            Over Iceland peak is midday, 12.00 -14.00 hrs – also highest sun angle and most planes fly above the weather – making plumes instantly visible to “Original Mk.I” eyeballs, usually two per pilot.

            Fact: All have radar and collision avoidance systems.

            Fact: All need clearances and minimum distance from each other is 15 miles (in non-radar controlled much more), this also reduces greatly the risk of any (one) flying into plume.

            Fact: All have radios and can and do report plumes.
            But of course Militay radar stations do this (scanning 24/7/365~6) and if anyone spots plume – report instantly to ATC as it begins to rise. Askja 1961 was spotted by military radar, and F-89´s were scrambled to investigate.

            Take it all the way. Living is dangerous.
            Close all roads; no more traffic accidents.
            No flying; no airline crashes.

          • island’er, aircraft weather radar does not “see” ash. Weather radar is optimized for weather (water and other round objects, like hail and such). Ash does not provide a ‘return’ that the radar recognizes, so it is ignored. You can fly right into it and never know it if you didn’t directly see it.

            Here is what a plume looks like to weather radar vs IR and VisSat imagery.


          • V.L. You are not interpreting correctly.
            I write of just “Plume”, “Radar” and your reference exactly says, Plume (close to erupting mountain, and has plenty of water content) is INDEED visible on RADAR.
            I say nothing on ash after it leaves the area, I never say WEATHER Radar either, or how it disperses, or if radar sees it then.

    • True and not true. There has been damage to aircraft from volcanoes and the ash is bad for engines, but i am not aware of any actual accident. Isolated eruptions are on occasions first spotted by aircraft. But there are effective warning systems on board and aircraft also warn each other (same as for local turbulence). But we have never had a large eruption into used airspace, so no doubt there are still lessons to be learned.

      • Also, aircraft (weather) radar is optimized for water and hail (eg, round things) and clouds of water in its various phases show up quite well. HOWEVER, airborne weather radar is almost useless picking up ash in the air (basically super heated, pulverized dirt with next to zero water content) and unless as a pilot you can physically see it with your eyes (daylight) you will never know it is there until the St Elmo’s Fire lights up your aircraft and you impact terra firma a few minutes later.

  8. Reading a book on the effects of Tambora and it was mentioning not only the fall in global temperatures but the effects of volcanos on storm intensities as well. It has a graph of the intensity of storms in Edinburgh Scotland and showed a peak at 1811 (1810 unknown) and 1816 (Tambora).

    • Interesting. In the polar regions (including the UK) the storms get their energy from the difference in temperature between the subtropics and the polar regions. So it is perhaps possible that the post-volcanic cooling increases the strengths of storms. 1816 was a very wet year in Europe , I believe (fact check needed..) which would indicate jet-stream weather. Tropical storms might get less intense as they get their energy directly from the warm ocean water.

  9. Maybe the volcano Gríms… wakes up?
    05.03.2017 22:03:27 64.298 -17.571 13.5 km 0.5 90.01 18.6 km SW of Grímsfjall
    05.03.2017 22:01:30 64.288 -17.562 3.1 km 1.6 90.06 19.0 km SW of Grímsfjall
    05.03.2017 21:44:01 64.294 -17.531 5.6 km 1.2 90.01 17.4 km SW of Grímsfjall
    05.03.2017 21:43:05 64.288 -17.562 3.9 km 1.4 90.03 19.0 km SW of Grímsfjall

    or only tectonic movment?

    • Tetonic alignment, but suspicious quantity of very small ones, making it now ongoing 45 min (And instant IMO re-calc rendering sizes above invalid, is highly noteworthy

    • It’s actually next to Thordarhyrna, so not directly Grims but related. Don’t want to be alarmist since it’s probably an insignificant event, but given the depths could be a small intrusion (or some kind of movement) maybe? Worth keeping an eye on for now. We don’t really know how this volcano works, so if this keeps going it might raise a few eyebrows, considering it *could* be on the way to waking up as we approach the “maximum” in that area. But let’s not get carried away! 😀 (I take no responsibility for a Daily Fail article from this comment! :P)

      • A few hours before the mentioned swarm there was a very interesting quake (M2.5) at Grímsvötn:

        05.03.2017 01:37:47 64.443 -17.201 2.1 km 2.5 99.0 5.5 km NE of Grímsfjall

        I think the pattern of quakes around Vatnajökull looks very much like one would expect during the last 6-20 months of runup before a Grímsvötn eruption.

  10. My post was not meant to be scaremongering but unfortunately the evidence points to the risk. As stated previously, aircraft weather radar does not see volcanic ash and, other than in clear daylight skies, a dispersed plume is almost impossible to delineate from meteoric cloud. In regards to monitoring and detection, there are limits to the speed of dissemination of information. I did a recent case study of the Pavlof eruption (paper in prep) and, despite seismic activity and a Pirep of the eruption, it was an hour before the NOTAM was issued and a full 14 hours before the plume position was being accurately mapped on forecasts. In the 15 hours post the eruption of Pavlof at least 12 aircraft were routed such that they were probably in an ash risk airspace and all at night.
    In regards to the NASA DC8, it experienced an unintentional encounter and the fact that the engines were older designs probably reduced the impact of ash ingestion. Modern engines work at higher temperatures and at much tighter tolerances than older designs,, making them more susceptible to silicate ash.
    Aircraft ash encounter is a known risk and currently being actively studied. Plume detection is still not fully reliable and the models for the dispersion and transport still under development. Consider a plume taken to 10+ km altitude, dispersed downwind at 100km / hr and aircraft approaching the area at 800 – 900 km / hr; two hours after the eruption will the ACC controllers have the information they need to safely route aircraft, that were 1600 + km away, 2-300 km downwind around the hazard ?
    As with any major eruption, risk to life exist in many forms. The way to safeguard is to recognise, study and develop systems to minimise them. Right now we need a cost effective and robust on board detection system for aircraft urgently.

    • And a comment from the peanut gallery (me)

      eagleowl61 mentioned that silicate ash doesn’t show up on radar. To give an analogy, light that we see is very similar to radar. Radar and Visual light are both electromagnetic energy, just at different wavelengths. We think nothing of the fact that we can see through windows…. yet windows are made up of a special form of silica that we call “glass.” Only in certain circumstances can you actually see the glass itself, mainly when there is a reflection off of it’s surface. Normal light, being of a much smaller wavelength, is more critical to roughness of the surface. Radar, being of a much longer wavelength, is less effected and passes right through.

      Re clouds and rain. Water vapor easily affects the dielectric constant of air, and this variation changes the incidence of refraction. It can also act as a reflecting surface. That is why radar (well, mainly radar designed for the purpose) can see clouds and rain squalls. And also the reason why antenna radomes and structures that RF energy has to pass through, is usually made from fiberglass.

      Caveat: Not an expert, I only have 20 some odd years of work in the field of radars and propagation. (retired Electronic Warfare specialist)

      • Ideally, use wavelength of radiation smaller than or similar to the size of the object you try to see. Ash particles may be micron size, so use micron-radiation, also called infrared. An infrared laser shining ahead might work? But that may not give you long enough notice in an airplane.

        • This is exactly why satellites are used primarily for plume detection and propagation tracking – the IR function of weather sats (GEOS – as an example) is infinitely better equipped to “see” the irregularly shaped, micron sized aerosol glass particles. Yes, any radar can “see” an eruption column and plume as it exits the vent supersonically, but at 10km ASL and 300km downwind – that is a different story.

          (Sadly, I have less experience than GL – I only have 11 years working fire control and ISAR radars on USN aircraft and an additional 10 years working part-time on airport ATC search radars.)

          • Did some work as a test target for an inSAR rig. Thing has some seriously spooky capability.

          • It certainly draws some pretty pictures. It can allow for positive ‘visual’ target ID when said target is well beyond visual range. Worked great for painting the masts of subs or drawing the superstructures of shipping vessels *way, way down range…*

          • … yeah, and the cute part about it, is that if the aircraft using it doesn’t use that mode, it’s as good as not being there. Human Error can still bite you in the arse.

  11. Nice swarm between Kilauea and Pu’o’o. Pressure may be increasing again after a few months of calm.

  12. This winter has been the warmest on record ever for us in the Faroes, with an average temp of 6,1C for dec-jan-feb, the previous record was in 2006 with 5,5C

  13. Swiss seimoslogical service says: 2017-03-06 21:12 4.6 Linthal GL probably not felt .
    Not so uncommon: 24 octobre 2016 Loèche-les-Bains – Valais – magnitude de 4.1.

  14. It was a IV strength earthquake and there are 187 comments that people had felt this earthquake the furthest location was 193 km away in Innsbruck.


    ,,Laying in bed in hotel with wife at 21:14 approx felt as if the bed was being shook similar to feeling of someone shaking their legs in bed and the mattress shifting. Enough to make us get out of bed and check how stable the bed was. The bed is totally solid and could not be moved by hand,,

    Other comments say it was also felt in Italy Austria and Germany.

  15. How can we see if the following eq are “non-volumetric change non-double-couple” (dixit Carl):
    08.03.2017 03:56:24 64.624 -17.442 11.4 km 4.0 99.0 4.5 km ESE of Bárðarbunga
    08.03.2017 03:55:32 64.623 -17.468 10.9 km 3.9 99.0 3.5 km SE of Bárðarbunga
    08.03.2017 03:52:44 64.615 -17.478 0.1 km 3.3
    (source IMO)

    • I asked Carl the same question a while back and he looks at the raw feed (unfiltered) waveforms for the quakes. I’ve no idea where he sources these from though…

      • Was interesting one a few hours previously at depth. Wednesday
        08.03.2017 00:18:28 64.596 -17.535 28.2 km 0.9 99.0 5.0 km S of Bárðarbunga

    • Interesting that these are on the SE side of the caldera. During the eruption, the bigger quakes alternated between the northwest side and the southeast side. Of course at the time the thing was sinking while now it may be coming back up (much slower than it went down though).

  16. Bogoslof erupted again at approximately UTC 0745 on 3-8-17 for about 3 hours, According to the AVO it’s the biggest eruption yet, it charged for about 2 weeks or so before blowing this time. It appears to be taking longer and longer between eruptions. The island is growing beautifully (even if it is just loose tephra that the Bering will eventually swallow up).

    Last night’s eruption:

    Replaced active link with static image as requested – admin

    • Dear Moderator,
      Was unsure how to upload an image, so i added the link, but it is actively updating, and will change with time. Can you fix it? you can also delete this message after correcting the previous post.

  17. reply to Beardy Gaz


    “Seismic signals combined with sparse GPS data released from the area seems to suggest that an eruption very well can occur at any time now, the time period could be anything from weeks to years. We will not really know until we see a persistant swarm moving from the current depth of 5km upwards to 2km or less.”

    [joke]Not sure if this is a peer reviewed paper, but interresting [/joke]

  18. An M3 on Mauna Loa. Nothing out of the ordinary but it had been a while since the last one of this size.

    • I noticed this on the EMSC-CDEM site:

      Magnitude mb 4.2
      Date time 2017-03-09 13:03:34.6 UTC
      Location 21.69 N ; 156.89 W
      Depth 10 km
      Distances 3772 km NE of Majuro, Marshall Islands / pop: 25,400 / local time: 01:03:34.6 2017-03-10
      109 km NE of Honolulu, United States / pop: 372,000 / local time: 03:03:34.6 2017-03-09
      61 km N of Kualapu‘u, United States / pop: 2,100 / local time: 03:03:34.6 2017-03-09

      • A couple of witnesses said it woke them up. One in Honolulu & the other in Kailua. Albert what was the time of Mauna Loa’s EQ? Was wondering if they felt Mauna Loa instead.

        • They were different quakes. The M4.2 was out in the ocean, next to one of the other island. It is not related to the Mauna Loa quake. Because of the location and strength, the M4.2 was more likely to have been felt.

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