Power of the past: 25 super eruptions – continued

The VC list of 25 super eruptions – continued

In our quest for major eruptions, we are continuing our journey around the world, moving north from Indonesia.

Kyushu, Japan

Japan’s southernmost main island is volcanically highly active. Past explosions have left large calderas, separated into two groups. In the centre of Kyushu is Aso, and it lies along a NE-SW graben. In the south are Kakuto, Aira, Ata and (submerged) Kikai, along the Kagoshima graben. Geologically, the island is caught in a fight between three plates (Eurasia, the Philippine plate, and further to the east the Pacific plate; the last two are subducting) and it is rotating under the pressure. This rotation has caused faults and grabens to form, and the subducting Philippine plate, which is quite young and warm, has been feeding magma into these zones for about 1 million years.

10. Aso (600 km3)

The most powerful eruptions of Kyushu have come from Aso. It also made the VC NDVP list. The caldera measures 25 by 18 km across. There have been four significant eruptions here, conveniently numbered as Aso-1 (265 thousand years ago, 50 km3), Aso-2 (140 thousand years ago, 50 km3), Aso-3 (125 thousand years ago, 100 km3, and Aso-4 (89  thousand years ago, 600 km3). (Erupted volumes, not DRE.) The last two volumes may have been underestimated. Aso-4 was by far the largest of the four eruptions. It left ash 15 cm deep at a distance of 1700 km from the explosion; pyroclastic flows covered the northern and central parts of Kyushu and even reached Japan’s main island, Honshu. It produced mixed magmas, partly rhyolitic and partly dacitic. It appears that mafic magma was injected into the magma chamber shortly before the eruption, at a depth of 14 km. Post caldera eruptions became basaltic.

The solid line gives the extend of the pyroclastic flows of Aso 4. Ishibashi et al. Earth, Planets and Space (2018) 70:137

11. Aira (463 km3)

This is located at the southern end of Kyushu. It lies at the top end of Kagoshima Bay, which is formed by a rifting back arc. The 17 by 23 km caldera and was produced 29 thousand years ago. The well-known Sakurajima volcano grew up on the rim of this caldera, a common event after caldera-forming eruptions. At the time this was a shallow water basin, separated from the bay by a ridge. (The bay was at the same level as now but sea level was 100 meter lower.) This was a double eruption, coming from pre-Sakurajima and from the central caldera. The eruption had an initial Plinian phase with pyroclastic flows, already reaching over 100 km3, which erupted from a vent near Sakurajima. The central vent exploded afterwards, erupting 300 km3; The second event created a much larger pyroclastic flows. Within a radius of 70 km, 40% of the land area was covered in 10 meter of pyroclastics. Compared to many other eruptions on the list, this was a highly explosive event.

12. Kucharo (175 km3)

Moving away from Kyushu to the north across Japan, we find this large caldera in Hokkaido which measures 20 by 26 km. There have been 8 caldera-forming eruptions here between 400 thousand years ago and 40 thousand years ago. The largest one of these occurred 120 thousand years ago, and it is estimated to have had an erupted volume of 175 km3 – a bit small for our list but large by any other measure! However, the caldera is very large and this suggests the possibility that the erupted volume has been underestimated. The eruption came from three separate vents, two purely rhyolitic and one with an additional mafic component. It began with a Plininan eruption but the main phase that followed had no strong Plinian phase. As in other cases discussed here, it is suggested that the eruption was triggered by injection of mafic magma into a silicic magma chamber.

Russia’s far east

This area is highly volcanic but remains under-studied. There is a fair knowledge on holocene eruptions but little is known about older activity. Kamchatka has the highest number of calderas per length along the volcanic arc in the world. Many show evidence of multiple eruptions. This is a high-risk area for large eruptions.

13. Opala IV (250 km3)

There have been four major eruptions from this volcanic field at the southern tip of the Kamchatka peninsula. The most recent, conveniently called ‘Opala IV’, was the largest. It is dated to 40 thousand years ago. The caldera is 12 by 14 km. The current Opala volcano is located at the northern edge of this caldera. The volcanoes here are basaltic to andesitic, however the ejecta of the Opala IV eruption are rhyolitic.The size of this eruption is poorly constrained, as neither the height of the stratovolcano nor the depth of the young caldera are known. Ignimbrites from this eruption are found throughout southern Kamchatka, over an area of 1800 km2. The ash was blow towards the NNE, where the ash was 25 cm thick at a distance of 300 km. The size of the eruption is uncertain, but it is believed to be the largest eruption in Kamchatka for 50 thousand years.

14. Pauzhetka caldera (400 km3)

Going back further in time, we find this caldera, also on the southern tip of Kamchatka peninsula. It measures 27 by 18 km across and is classed as a volcano-tectonic depression. The centre of the caldera shows a resurgent dome; around this dome are areas of hydrothermal activity. The eruption that formed the caldera 420 thousand years ago covered much of the southern part of Kamchatka in the so-called Golygin ignimbrite. The volume is derived both from the ignimbrite and from the volume of the depression. Two thirds of the ejecta was deposited near the crater and the rest was blown southeast towards and across the Pacific Ocean.

Kurile Lake (image source: wikipedia) is a caldera 14 by 8 km in size. The largest of its eruptions occurred only 7000 years ago, however it didn’t make the list, at ‘only’ 150 km3. It is located inside Pauzhetka caldera.

After the Kuriles we arrive at the Aleutian arc and Alaska. This area has had frequent and very significant eruptions, but not quite large enough for us. Moving on, we find the western continental US. And it is a whopper.

The Aleutian Fisher caldera measures 8 by 16 km. It is located on Unimak, and coincides with a gap in a series of volcanic mountains which leaves little doubt about how it formed. The explosion is dated to 9400 years ago. Pyroclastic flows crossed the 700-m-high Tugamak Mountains 15 km to the north, and deposited a 20-meter thick layer on the far side. The total volume of the eruption is poorly constrained, but based on the caldera and the ignimbrite, a value of 119 km3 has been suggested. That is not quite large enough for us.

The Snake River – Yellowstone volcanic province

The western US has had enormous eruptions starting more than 30 million years ago. The older calderas run from Nevada to New Mexico. The more recent ones cluster around the Snake River, along a hotspot track. This hotspot has made history. It began with the Columbia flood basalt around 18 million years ago. After it moved further in-land, it left a series of calderas, culminating in three major eruptions at its most recent location, Yellowstone. Yellowstone is the largest known caldera on Earth, with a diameter of 85 by 45 km. There were three major eruptions here, two of which qualify for our list. The other one, Mesa Falls, erupted 700 km3 which makes it a high-VEI-7, impressive and destructive but smaller than the other two. Yellowstone produces both basaltic and rhyolitic eruptions. The large explosions produce rhyolite.

15. Lava Creek (1000km3)

This was the most recent of the three major eruptions of Yellowstone. It is dated to 630 thousand years and spread ash across much of the US. The deposits are 200 meters deep around the caldera. Recent research has shown that the eruption consisted of up to four distinct events, where two of the events were separated by enough time that the earlier ejecta had cooled. In the case of the Katmai eruption (1912), such cooling took two decades. The time interval between the events of the Lava Creek may have been as long as 170 years, sufficient for it to be considered two separate eruptions. Analysis of crystals show that the magma reservoir received fresh heat in the period of 1000 to 10,000 years before the eruption, suggesting that the eruption was triggered by an influx of new magma into a cooling reservoir.

16. Huckleberry Ridge (2500 km3)

This was the first large Yellowstone event. The eruption occurred 2.1 million years ago and it blanketed half the US. The eruption occurred in three pulses. The third pulse may have been a separate event as it was fed from a different magma source. Recent research shows evidence for reworking and cooling of the deposits between the phases, and suggest that the eruption may have been episodic, over years to decades. (Elliott Swallow, in a 2019 paper, raises the question how close together in time eruptions need to be to count as one event. For current eruptions, a year may be too long, while for ancient eruptions, events a century apart may still be viewed as one event.) The reported volume includes all three pulses. If the last one is excluded, the total drops to ‘only’ 2000 km3 ejecta.

17. Kilgore (1800 km3)

Before Yellowstone, the hot spot lingered at the Heise volcanic field, along the Snake river valley. Eruptions here occurred between 6.6 and 4 million years ago. There were a number of basaltic lava flows, and four rhyolitic explosions left ignimbrite deposits. The last of these four is Kilgore, dated to 4.5 million years ago and it is believed to be the largest: the tuff is found across Idaho, Montana and Wyoming. The thickest ignimbrites are a few hundred meters deep. There is no known caldera in the Heise field: the area was covered in deep lava flows some time after the major eruption. The lack of knowledge on the caldera means that the eruption volume is uncertain. The number given here is conservative, but on the other hand assumes that it was generated in a single eruption.

From Watts et al., 2011, Journal of Petrology

California to Colorado

The Snake river volcanics are hot spot related. But in fact the western US has had similarly-sized eruptions also in places without hot spot activity. The focus of activity was around Nevada, around 30 million years ago. This includes the Wah Wah Springs eruption which is often included in VEI charts. This particular eruption I did not include because of age, and because of a lack of independent confirmation of the size and nature of the eruption. That is not a great loss, as there are other similarly-sized candidates in the region.

18. La Garita (7500 km3)

This eruption is considerably older than others we have looked at, but is included because of its size. It is sometimes claimed as the largest eruption (VEI) known. It is the source of the Fish River ash, and has been dated to 28.1 million years ago. The caldera is located in the San Juan Mountains in southwestern Colorado: it is one of a cluster of calderas within the San Juan volcanic field. A volcanic shield once covered much of the southern Rocky mountains but it has eroded a lot. The field lies at the head of the developing Rio Grande rift, a region of extension. The caldera measures 35 by 75 km and it formed in three steps during the La Garita eruption. The eruption was dacitic, and produced an ash flow 50 to 300 meters thick, as far as 100 km from the caldera.

The calderas of the San Juan volcanic field. Source: USGS

The volume is often quoted as 5000 km3 (DRE). This is based on estimates by Lipman, who assumes that the outflow extends to 75 km at an average thickness of 100 meter, and adding 1 km depth of deposits inside the caldera. If I instead assume that the thickness linearly declined with distance, and adding the caldera in-fill, I find 3000 km3 DRE, or 7500 km3 ‘VEI ejecta’. This illustrates the uncertainties that are implicit in deriving volumes for ancient eruptions, and the need to be cautious about the most extreme values. Even with the lower number it is one of the largest eruptions on our list, but it may not qualify for VEI 9!

19. Monotony tuff (7500 km3)

But La Garita did not stand alone. The Monotony tuff layer is found over much of Nevada and is part of the same series of Nevada ignimbrite eruptions 30 million years ago. The region has many similarities to the more recent activity in the Altoplano. At the time this was a high plateau with thick crust (60 km), above a subduction layer. It is sometimes called the Great Basin altiplano. The monotony tuff is dated to 27 million years ago. It is identified with a caldera which may be as large as 75 km (gravity measurements suggests it may be a composite) and the composition of the tuff is remarkably uniform over the full range. The thickness reaches 500 meters in places. The volume is uncertain but I have used one of the more conservative estimates (3000 km3 DRE). The uniformity makes it likely that this came from a single eruption. It rivals, and possibly exceeds, La Garita.

20. Long Valley (600 km3)

This eruption is separate from either the Snake River or Nevada events. The caldera is in eastern California, along the Sierra Nevada. It measures 17 by 32 km. The eruption that formed the caldera happened 760 thousand years ago. It formed the so-called Bishop tuff, erupted in a 90-hour long, Plinian event with an eruption rate which increased with time. The eruption may have migrated along the ring fault. The eruption was rhyolitic. However, the same volcanic system has also produced basaltic eruptions: this mix is quite a common feature of these large eruptions. The magma chamber had been present for over a hundred thousand years, in a cool, crystal-rich state, but had been reheated into an eruptible state shortly before (perhaps by a thousand years) before the event.

Central America

21. Atitlán (1200 km3)


This famous Guatemalan location has been active for 14 million years: Atitlán may stake a claim to being the oldest volcano on the planet which is still erupting. It is very unusual for one region to show volcanic activity over such a long period. There have been 3 eruption cycles leading to caldera collapses. During the first eruptive cycle between 14 and 11 million years ago, what is commonly called the María Tecún Tuffs was ejected, with a total ejected volume of 2800 cubic kilometres. It created a caldera 15 by 25 km. The tuff forms five separate layers which were erupted at different times: two of the layers show a magnetic pole reversal compared to the others. The largest of the layers (MTT II), 11.6 million years ago, produced ash covering most of the United States, and created a solidified tuff sheet up to 700 metres thick. Using road cuts, drill samples from mines in Mexico, and distal ash finds in Pensacola, Florida, it was calculated to have been around 1200 cubic kilometres.

After the eruption a new cycle of volcanic growth and caldera formation began. The Atitlán II Caldera formed during the San Jorge ash flows 10 – 8 million years ago, a series of VEI-6 eruptions. One million years ago the current Atitlán III Caldera formed during the 350 cubic kilometres Los Chocoyos eruption. It confirms the pattern that major calderas are repeat offenders.

Europe

The most famous major eruption in Europe is that of Santorini (not Vesuvius which was locally devastating but globally not as significant). But this volcano is also a repeat offender: it has had four caldera-forming eruptions, 180,000 years, 70,000 years, 21,000 years and 3600 years BP. The final eruption destroyed a local civilization, caused a devastating tsunami, and deposited up to 80 meters ash, blown mainly towards Turkey. The four eruptions were probably of similar size. However, these eruptions were around 100 km3, too small for our list in spite of their fame. Europe lacks VEI-7 eruptions. There is however one European eruption which can be added to our list.

22. Campei Flegrei (250 km3)

The largest eruption known in Europe is Naples’ Campi Flegrei event, 39 thousand years ago. It deposited the Campanian ignimbrite across Europe, Russia and North Africa. There was an initial phase with a volcanic column at least 40 km high, followed by collapse and creation of the caldera, a rejuvenated volcanic column, and widespread ignimbrite deposition extending 1500 km from the eruption point.

The caldera has a maximum diameter of 13 km, not quite in the same league as the very largest eruptions. However, it devastated a continent (admittedly Europe is not the largest of continents). 250 km3 of ash was ejected. On the opposite side of the Bay of Naples, 35 km away, the pyroclastic deposits are 40 meters thick. The eruption was followed by a second event 10 thousand years later which formed the Masseria del Monte Tuff: this ejected 16 km3 (DRE). There was a third event of similar size 15 thousand years ago.

The African rift

The volcanic history of Africa is not well known although volcanoes are present along the African Rift. Ethiopia in particular may be the proud owner of the most underestimated volcanic risk in the world. Here, over 10 million people leave within 30 km of a volcano that has erupted within the holocene. And it has some impressive, but little studied, scars.

23. Awassa (1000 km3)

Awassa is the largest of these scars, an eroded caldera which measures 40 by 30 km, partly overlapping with the more recent Corbetti caldera. It is near the Africa rift valley. The caldera is intensely cultivated. The deepest part is occupied by Lake Awassa, the smallest of the Rift valley lakes. Nearby Aluto had a major explosive eruption 310 thousand years ago but this was dwarfed by Awassa. Vogripa lists it as 1000 km3. Along the western wall of the caldera, a major fault exposes more than 250 m of tephra. The main eruption is dated to 1.27 million years ago.

Lake Awassa

24. Munesa crystal tuff (1100 km3)

This a tuff layer between 250 and 400 meters thick, prominent along both sides of the rift valley in Ethiopia, around Guraghe. The originating caldera is missing; it may have been buried underneath lava flows within the rift valley. The tuff is dated to 3.5 million years ago. The tuff was capped by a lava flow.

25. Ngorongoro Crater (500 km3)

Eruptions can be powerful by volume and energy. But they can also be powerful in what they create. The best example of that is Ngorongoro Crater on Tanzania’s Serengeti. There are three other calderas nearby, all natural wonders, but Ngorongoro tops them all. It is reputedly the largest complete caldera in the world, and home to the best of Africa’s wildlife. It is 18 km across, and is the remnant of a shield volcano. The volcano was active between 2.3 and 2.0 million years ago, when it was within the African rift: the area has since been uplifted. Very little is know about the climactic eruption: it is likely to have produced the Naabi ignimbrite, a 20-meter thick layer in Olduvai Gorge, but the size (and how much was rifted lava) is unknown. Based on caldera size, the erupted volume may have been up to 500 km3.

Patterns

This list of 25 began with the desolate magnificence of the Altiplano, and ended with the most evocative caldera on the planet. What can we learn from this list? The list is itself incomplete, and every reader will know of one or more eruptions that could or should have been included. A VEI 7 eruption may happen perhaps twice per millennium. Over the time span of several million years covered in this list (ignoring a few very ancient ones), there may have been 5000 VEI-7 eruptions. A list of 25 just doesn’t get close.

Accepting that this list is incomplete and badly biassed, we can still point at a few interesting aspects.

Very few of the listed eruptions are in the tropics. That is unlikely to be a real effect. Toba shows that the tropics can do anything that the rest of the world can. Why is Central America only in our list through an ancient eruption? What happened to the tropical eruptions? The most likely cause is that the high rate of erosion removes the signs of ancient calderas. The best cases of old eruptions are found at dry mid-latitudes, especially in the high Andes where rain is a rare event and scars survive almost forever. Elsewhere, the book of volcanic history is erased year by year.

Many of the calderas in this list are repeat offenders. A location that managed a VEI 8 has a high probability of doing it again, albeit typically after a wait of 100 thousand to a million years. The waiting time is in part because of large amount of magma that needs replacing. At the top end, for a high supply rate of 0.01 km3/yr, it takes 100 thousand years to provide the 1000 km3 of magma – this is enough for a large VEI 8. This is the minimum time. Taupo is an example of such a fast system. Other areas take longer to build up to a VEI 8. Several conclusions can be drawn:

(1) Magma supply rates of super eruptions are no higher than that of other volcanoes. High magma supply gives frequent eruptions – not larger ones. When an eruption happens depends on the magma pressure versus the strength of the chamber roof. A faster magma supply rate just causes an earlier eruption.

(2) The cyclic eruptions show that super-eruptions do not completely destroy the magma chamber(s), nor the feeding conduit. This is easy to understand for trapdoor calderas, and makes sense for caldera collapse, but is more difficult for massively explosive eruption. Indeed, there is limited evidence for major explosions: ejecta from Plinian eruptions are often minor or even absent in these eruptions. The main eruption mechanism may be fountaining along the caldera rim.

(3) The magma indeed stays in the chambers for a very long time. The evidence for this comes from the large fraction of crystals in the ignimbrite. The magma chambers appear to be fairly cool, around 700-900 C, but able to keep this temperature for a million years. Some of the ignimbrites show evidence for episodic heating, including shortly before the eruption. In those cases the super eruption may be triggered by intrusion of fresh, hot magma into the massive chamber, either remobilising the stale rhyolite, or re-melting the crystal mush.

We can expand on this. The locations of the super eruptions tend to show two different eruption types: smaller mafic eruptions, and massive silicic ones. The magma evolves to silicic during the long wait in the chamber. The magma originates as mantle melt, which over time incorporates crustal melt. The magma chamber may have supported a flood basalt eruption, where again it takes a million years before the silicic super eruptions may start (remember that flood basalt eruptions themselves were excluded from this list.) But many eruptions show evidence of mixed magma, where the eruption is finally triggered by injection of new, hot (mafic) magma into the mushy reservoir. There are several cases where eruptions come from several magma chambers, possibly with some intervening time. The reheating affects several chambers in the region, not just one. This heating of an entire region may help explain the exceptional size of the calderas.

The eruption rates deserve a further look. The super eruptions appear not to be particularly long lasting. They are not like Eldgja or Laki, lasting months to a year: the duration of the overall event is limited. Toba is a good example: this eruption appears to have lasted little more than a week. But this requires exceptionally high eruption rate. For Toba, the average rate was of the order of 10 km3 (DRE) per hour. Instantaneous rates during eruption pulses may have been much higher. These rates are far too high to maintain a tall convective column: the weight of the ash collapses the column of air. This limits the height the ejecta can reach. Some of the ash reaches altitudes of 40 km, but the majority stays well below this. The collapsing columns may in fact be the cause of the huge ignimbrite sheets. Super-eruptions come in a variety of shapes and sizes, but they should not be seen as scaled-up versions of Krakatau.

What causes super eruptions? The distribution across the Earth shows that the largest such eruptions happen where oceanic crust subducts under very thick continental crust. This happens under the Altiplano where the crust has thickened to 70 km. It is also seen at Yellowstone, and in the past under Nevada. The oceanic crust provides the melt, and the thick crust provides the extremely strong lid which can hold the pressure for a million years. The oceanic crust is an essential ingredient, as shown by the fact that the equally thick crust of Tibet does not show super eruptions – its crust comes from a collision of two continents. As an aside, this also indicates that the hot spot of Yellowstone does not on its own explain the super eruptions there. The subduction and thickness of the crust are also important ingredients.

The second type of location where super eruptions can occur are in areas of extension within continental crust. This is the case in Taupo, Kyushu, and Ethiopia, all of which are developing rifts. Naples, although smaller, may also fit this type. Toba is also located in an area of some extension, and is located on the Sunda continental plate. This also explains why Sumatra has these eruptions, but islands east of Java do not, as they are not part of the Sunda plate.

The listed eruptions in Russia do not fit either description. Alaska could be included in this. These eruptions are smaller (VEI 7), more recent (i.e., more frequent), and are in regions of very fast subduction. It appears that this is the pattern of volcanic arc: frequent, large, but not quite super. Perhaps the magma chambers cannot grow to sufficient size in the absence of sufficient continental crust.

Conclusion

Our search for the elusive super eruptions has thrown up some interesting findings. These events repeat in the same location over a few hundred thousand to a million years. They favour locations were there are at least two out of three conditions: subduction, excessively thick crust, and rifting. These conditions allows a magma chamber to mature for a million years. Of the ones we selected, only Yellowstone coincides with a hot spot, so this is not an essential ingredient. The hot spots of Iceland and Hawaii did not feature in the list. Finally, even though we called these ‘super’ eruptions, the events tend not to be strongly explosive. This is probably related to the lack of explosive power: the chamber roof does not collapse, and neither the magma chamber nor the conduit are damaged in the eruption. The sheer size and eruption rate may prohibit strong explosions. This makes super eruptions survivable (at a distance, at least). Some newspapers might be disappointed.

At the end of our journey around the world in 25 eruptions, we return to the story of Mikhail Goldstein. There is a link between volcanic war zones and music. In 2010, the violinist Eric Silberger was traveling to take part in the Menuhin competition in Norway. He never arrived. His flight was cancelled following the eruption of Eyjafjallajökull, and instead of playing a competition in Norway, he ended up entertaining stranded passengers in Newark airport in New York. In 2014, he finally managed to settle the score, when he became the first violinist to play inside a volcano. Silberger performed Paganini’s 24th Caprice in A minor, inside a cave in Thrihnukagigur, a dormant volcano near Reykjavík. It has the reputation of being an exceptionally hard piece to play: it must have seemed appropriate for the location.

Reports say he gave a fiery performance. Whether it was a super performance is not recorded. But just like Goldstein silenced one of the worst battles of the second world war, Thrihnukagigur has not erupted since. In the battle between music and volcanoes, the score is a draw.

Albert, August 2019

116 thoughts on “Power of the past: 25 super eruptions – continued

  1. Fabulous piece Albert!

    I can hear the “whut?” all the way home from the Yellerstoners as they are trying to bend their head about the mobility part of the calderas there.

    GL Edit
    : @Tallis, Carl didn’t do it. I did. 😀

    • Well, whoever did it it was one of the top bits of writing here, beautifully and clearly written and strangely with a narrative.

    • I was referring to the wandering comment. The article is an Albert/Carl creation with minor opinions and snide comments thrown in from the rest of us in the back channel.

  2. First!
    I thought the 300 km3 value was DRE and not bulk for the Campanian eruption.
    How does DRE volumes work with caldera forming eruption like this.

  3. What makes La Garita 7500 km3 ?
    Its 5000 km3 in all other measures
    Albert explain here… is it because the Fish Canyon Tuff deposit is so very thick far out from the vents?
    La Garita lacked a plinian phase right?

    La Garita was crazy Imagine all the volcanic ligthning .. so much ligthning its beyond insanity IF La Garita was photographed in long exposure.
    Calbuco s ligthning is sourely nothing in comparison.

    • You still do not get that you would not survive that kind of eruption if you are within photography distance. Neither would the camera, nor the memory chip.

      • and all that electro-static interference from lightning and ash would negate any cellular-based uploads as well….

      • Well… the ash would effectively be transparent unless it got damp. Most antenna radomes are made of fiberglass, a high silica material. It has to be specially treated or coated to become opaque to RF energy.

        I’ve played that game personally when some idiot used a metal based paint on one of my receiving antenna radomes.

        That “DO NOT PAINT” stencil has a very specific meaning. It was a very pretty coat of paint, but it made my system essentially non-functional. The only radar I could see was 10 meters away on the flying bridge if I disabled blanking for it. {Intercept receivers are electrically turned off when the main pulse for an own-ship radar fires} Any time a radar has work done on it that affects its pulse configuration, you have to review and tweak your blanking system so that you don’t see it but keep your receivers wide open when the radar is in receive mode. And yes, you have to add a little bit of extra slop in your blanking pulse to allow for the radar pulse to bounce around the superstructure, which it will do. occasionally you get spurious harmonics in there from two systems mixing their signal on non-linear metal junctions. (effectively diodes where two loose pieces of metal touch and develop a little bit of corrosion) Drive two RF signals into a diode junction, you get the sum, the difference, and the two originals. Example. 9Ghz and 9.8Ghz → 0.2Ghz + 18.8Ghz and the original pair. And those can in turn mix with other signals. It can get electrically noisy very very fast. EW isn’t just about finding and evaluating radars, you have to stay on top of stuff that can mess up your gear’s capability.

      • I wonder what an eruption that large does to the atmosphere, in terms of breathability, on a global scale. CO2 goes up, but enough to asphyxiate animals?

        • That would require CO2 in the per cent range, while at the moment it is 0.04 %. That would not happen. Locally, volcanoes have done this, when CO2 build up in water. But most CO2 from volcanoes does not come from eruptions: it is emitted slowly from magma chambers under dormant volcanoes. SO2 is different, as that comes out in the eruption. That will be far more dangerous.

        • Would you be thinking of those two African crater-lakes, whose infamous over-turns release enough CO2 for the low-lying, toxic cloud to asphyxiate locals ?
          They now have ‘soda syphons’ to mitigate deep CO2 build-up…

          IIRC, volcanic ‘extinction events’ correlate with mega-continents *plus* sub-aerial (on-shore) magmatic provinces *plus* deep-ocean hypoxia due poor stirring. At present, we seem to lack the makings. The High Andean contender lacks ‘back arc’ spreading, the Red Sea triple junction is rifting too slowly, the sprawling whatsit in mid-Pacific is safely, deeply submerged…

          Another take is that such magmatic provinces causing the greatest harm seem to have begun with a CO2 mega-burp due ‘cooking’ of carbon-rich strata by the rising magma. Then, having ‘broken wind’ with that foul opening salvo, the eruption pumps out lava, ash, acids etc etc in the usual way.

          If so, the magma must rise through thick continental carboniferous and/or carbonate deposits, restricting the list of potential perps…
          YMMV

          • Sadly, we don’t need a large igneous province to get end-Permian scale CO2 belches. We’ve been cooking carbon-rich strata in engines and power plants for over a century. And we have worsening “dead zones” in the oceans due to eutrophication and pollution of various sorts. Poor stirring? If Greenland’s ice starts to go in a big way it will shut down the thermohaline circulation …

          • Actually, this is a point where the jury is out.
            Shutting that down would require the ice to melt at a pace not predicted, and it would only happen on a local scale.
            Yes, it could shut down one of the engines behind the circulation of the great oceanic currents, but only one. And only if the Antarctic would remain Ice free year round. And that is quite out there.

          • I was actually thinking about the CO2 chamber we used to use to euthanize laboratory mice, but sure, inversion layers at African volcanoes, good point.

    • The 5000 km3 comes from a single group. They explain clearly how they derive it but I had difficulty getting the same number. So I did my own calculation. But I think you are confused about DRE versus erupted volume. The 5000 was DRE, and would have been more than 10,000 erupted volume. The 7500 km3 is erupted volume, which I used because it is what the VEI scale uses. When you see a number quoted, check which one it is.

    • While majoring in geology, I spent time studying the different ash flows out of Yellowstone. I stood at the base of one of the Huckleberry Ridge units, and it towered over me like a sky scraper! And that was over 50 km south of Yellowstone… anyone standing there admiring the fireworks during the eruption would have been disintegrated.

  4. Side note for the transient reader.

    Campei Flegrei occurred right in the middle of the home range of the Neanderthals. This stressor likely put them on the road to eventual extinction. Their only recourse? Breed or die. This may explain some of the reasons why moderns carry some Neanderthal DNA.

    • Basically the Neanderthals were big muscular guys, enter cro magnon girls looking for a hunk…
      Sad cro magnon guy went into the forest for a cry after losing his girl, up comes muscular Neanderthal cougar and carries him further into the woods for some pampering…
      Nature at its best.

  5. Loved this series Albert! Living in the heart of the Columbia Basalt and the nearby Snake River valley, I’m of the opinion that Carl expressed a while back-Yellowstone’s taking a dive under the Rocky Mtn Batholith-it’s not going to be as active…
    But let a hotspot do a phacriatic phart. and watch the Daily Fail et,al go nuts…

    • There will be a post on that one in a while.
      This is just to complex to answer in a comment, because there is a big difference between Yellowstones hotspot and other hotspots, and also the crust and it’s trajectory has effects, that need to be explained.

  6. What I find really mind-blowing is how most of the continents ecosystems and species recovered after the really ashy eruptions, especially large animals. I guess the populations have been regularly reduced to a very minimum from which they bounced back.

    The amount of ash is variable, but still… no grass for months or years in most places, not too many tree leaves left, not-too-healthy volcanic ash topping on every kind of food, fish ‘breathing’ a mudbath….

    Life resilience is amazing.

  7. How thick of a continental crust is too thick? Some workers think that Yellowstone’s days are done because the crust continues to get thicker as the track translates to the east.

  8. As I’ve said for years on here… The combination of magma supply (subduction) and rifting seems to be the best way to find areas prone to these massive eruptions. Even when you don’t get vei-8’s, you see more prolific and explosive volcanism.

    Rifting not only can create or assist in producing fresh melt, but it can also help expose a once deep magma chamber to a weaker lid / roof, allowing events such as Toba’s eruption to occur.

    • Also, going back a little further in history, we have what are known as silicic large igneous provinces. These areas are similar to flood basalts in the amount of magma produced, except the magma was produced from explosive eruptions. Most theorize that taupo volcanic zone is a very small and young example of one of these areas.

      Whitsunday is the largest known of these provinces (since extinct by many years). It would have had the equivalent of a VEI 6 eruption roughly every year based on the amount of magma produced there… Other examples include the Sierra Madre Occidental in Mexico, the American Southwest during the ignimbrite flare-up 50 million years ago, and other areas near Brazil / the red Sea. There is speculation that the Fish canyon tuff was actually dwarfed by some eruptions in these areas near Brazil and the red Sea, but research is scarce here.

      What do they all have in common? Rifting. The more violent or large examples include instances where landmass was sheared away from a continent.

      So in short, I think rifting is highly underrated or under appreciated when it comes to understanding volcanoes and how they can affect the earth.

      • You are absolutely correct.

        Rifting is definitely a factor in many large caldera events. In some even prima causa.

        People tend to either associate these caldera formations with either a plume or with subduction only. But, as soon as you start digging in to them you almost inevitably find a rift.

        But there is conundrum to it, was the rift created by the event? Or was the rift one of the causalities? For most places it is impossible to answer, well with two glaring exceptions that I know of.

      • I expect that in the far future, the Altiplano may appear to be a silicic province, from adding together all the individual eruptions. Rifting is important for many of the super eruptions but not for all. And you do need to retain a strong crust. If you weaken the crust too much, you get lots of small eruptions (think Hawaii) but nothing super. And it needs to be continental crust. Once the crust is rendered so deep that oceanic crust begins to form, the time for super eruptions is over. They occurs along the African rift but not along the two other arms of the triple point.

        • I do not think CBUS only meant rifting as in the larger rifts.
          I interpreted it as being both faults, localized rifts, and grabens. If so, it is true. Otherwise not so much, just partially.

          • Correct. Alternatively, slab gap hypothesis with sinking slabs opening a window in the mantle also plays a big role (related to rifting).

            Not coincidentally, two of the regions I’ve paid the most attention to are theorized to be undergoing this slab gap scenario now. Those being the Kagoshima graben in Japan, and the Klyuchevskoi region in Russia. I probably won’t be alive to find out, but I tend to think both of these regions are developing and growing into future Taupo type regions. Kagoshima is already close.

      • Interesting! The Afar flood basalts and when the EARS started rifting 30 My ago had some of the largest both explosive and effusive eruptions since then, including those Yemen eruptions that sent ash over the Atlantic. Though as Albert said you do need to retain the strong crust, evidence for this, Afar has long stopped producing large explosive eruptions, There is also a general lack of large calderas across its floor, the only area that seems to still produce eruptions reaching VEI-7 is the Nabro Range in the Danakil Alps which as expectable is a thicker block mostly unaffected by rifting so far.

        Taupo is one of the best examples which was clearly caused by the rifting, the Lau Basin started spreding at its northern end near Fiji as the Tonga trench rapidly retreated, here the Lau Basin is currently rifting faster than the East Pacific Rise. As the Lau Basin propagated southward towards New Zealand it formed the TVZ there. As rifting keeps going it will eventually form oceanic crust which should mean the end of Taupo? though the silicic volcanism might just migrate southward, not sure if the Chatham Rise would allow that though.

        Kyushu has a remarkably similar setting but with a weaker back arc? The Marianas are being teared appart by another back arc rift which might eventually propagate into Honshu or might be starting to do so.

        But there are cases where it doesn’t seem necessary like the Yellowstone Hotspot or the Altiplano. Now, if rifting started in the Altiplano that could get apocalyptic.

        • To clarify, rifting on its own doesn’t create these environments. As Albert said, you need strong crust to build the requisite magma.

          My theory is more that the transition of continental crust to rifting is what causes these enormous eruptions to be possible.

          If you have crust that has a very deep magma pool… IE a batholith at the moho, it probably won’t erupt ever. But if you take that developed magma pool and slowly thin and weaken the crust over it’s too over a period of millennia, you suddenly get a very different situation. Not only does the rifting weaken the overlying crust and make it much more shallow, it also helps to melt the surrounding bedrock and crystallizing magma to form lots of reinvigorated rhyolite.

          This combination in my opinion is the “cookbook” for these large caldera systems.

        • I wouldn’t totally discount the possibility of rifting being a factor at Yellowstone and the Altiplano, either. Sure, there’s no rift all the way down to the MOHO at these sites, but the stress field from all the huge mountain masses pressing down on the crust like bricks on a mattress could be creating local areas of shallower extensional forces. They’d only need to extend from the surface down to the magma chamber to contribute to supereruptions.

          Is there evidence for such shallow, local areas of extension in the crust around mountain ranges?

          • Yellowstone = Hebgen, nice little faultline. There are more of them obviously, but Hebgen is substantial.

            The Puna-Altiplano is riddled with faults and Grabens.

            What I am saying is that your are correct Fluid.

  9. Had an interesting day at work today (working at a plant nursery), as some of you may know I’m from the Faroes, our work is mostly (beside selling trees/plants to everyday people) to figure out what plants can actually grow here, as a general rule of thumb, they have to be quite hardy.

    Anyways, a few of us went to this old timers garden to get cuttings from a bunch of his plants, while he shows us around his garden he points to this and that. “That one comes from the highest volcano in New Zealand, ‘rhubppu’ or something like that”, “This one is from Kamchatka, those from the Kurils”
    Turns out a whole variety of the plants he has are from volcanic regions in the world, some of which I know already, but it was a bit of an eye-opener and my work has suddenly become considerably more interesting.

    Something awesome (which I guess is unique) from his garden, he has a Larix gmelinii, which happens to be the northernmost tree in the world, right next to a Nothofagus antarctica, which is the southernmost tree on earth. We have quite a few plants here from Patagonia and the fire country.

    So yeah, by chance got thrown a volcanic perspective into my everyday work, which I quite like already, I’d call that a score!

    • We grew a Nothofagus once. It was supposed to become a small tree but it hadn’t gotten the message and grew 15 meters tall. Beautiful tree and the birds loved the branches. If we had known we could have planted it somewhere suitable. Not where it ended up. We can tell from experience that this tree does not appreciate coppicing. RIP

  10. Grimsvötn is a pretty impressive beast for being a thin crusted mature mid ocean ridge – Hotspot combination / interaction.
    I know that Grimsvötn cannot do a large VEI 7 and haves a hard time doing a big VEI 6.
    But it sourely does big VEI 5 s sometimes

    Whats impressive with Grimsvötn is that all of these plinian eruptions are quite fresh to fresh basaltic magmas thats not some old evolved gassy sludge.
    The really really impressive Grimsvötn stuff
    The 3 ( 30 km3 ) Plinian events of Sakursunarvatn eruptions where basaltic too.
    As far as I know Grimsvötn is the only holocene basaltic volcano on Earth thats Done a mafic Big VEI 5 eruption.
    But Masaya Done some huge Basalt plinians too.

    • Nope, both Bardarbunga and Grimsvötn have done VEI-6s as basalt eruptions. Pretty darn impressive. And, 5 is the number for the Saksunarvatn tephras.

      But, this is not the article for gushing basalt floods.

      • Carl I meant VEI 6 basalt plinians : )
        Basalt plinians are extremely rare
        Sometimes it feels that only Grimsvötn does basalt plinians today

        • In a sort of a way Jesper, given that VEI-3s is a bare minimum.
          But, I think this is a subject for the next Grimsvötn post…

      • Ulawun seems to have recently done a couple of good sized (not VEI6 though) basaltic eruptions. Ash to FL630 with high fountaining.

        • Spaceweather seems to talk about sulfur stratospheric injection.
          I think it just did a VEI4 if not more. It’s in a remote area, so our best data is from satellite.

        • Never believe Flight Level warnings.
          They are there to protect airplanes, so they are normally off by a factor of 3.
          So, basically we are talking about an eruption with an ash column 6000 meters high.
          And stratospheric injection is just ludicrous from a fountaining volcano. Up until we have verification of it being anything significant, let us stay a bit calm.

          • Carl, Ulawun seems to have erupted up to 19km. That’s quite significant, though not huge.

          • Optical confirmation and photograph by an airline pilot. It was 13km. There is no evidence of higher elevation on any of the paroxysms.

            Unless someone can come up with a reliable source for higher altitudes, I will go with what is there. And that is at best a borderline VEI-4.

          • For all. Those Mastin et al equations I keep using for mass ejection rates based on plume heights are a work around for volcanoes going off in remote areas with little to no instrumentation. They are designed to give realistic source parameters based on of space data. Even Mastin et al gives an uncertainty factor of four either way in the resulting estimates.

    • I think I missed something in translation…

      “There are pleasant walking trails in the vicinity (but not to the top) of Komezuka, however, easy access by public transportation is not provided.”

      • That’s the polite Japanese way of telling you the train doesn’t go there.

    • Hm, here is the thing. I have a problem finding which volcano that would be. Guess work would be Hofsfjökull or Tindfjallajökull or Torfajökull.
      I can’t see any other options.

      • I don’t have a single idea how any series of eruptions could produce a sulfate spike of that size with very little geological evidence.

        • Oh, that is not a problem, it happened during the glacial period. All evidence melted away as the ice melted. Only remaining thing would be a nice nested caldera (or two).

          There is actually a point to be seen here. And that is that ice reinforces the crust of sorts. It increases the amount of magma that the crust can hold. This is the reason why the largest explosive eruptions in Iceland since deglaciation occurred at Grimsvötn, it quite simply has the most support from the glacier. Another Oomphy bugger is Thordharhyrna, lot’s of Ice.
          So, any series of eruptions would just have left a nice hole in the ground.

      • Carl and Tallis, I am happy to provide you with the answer!!!

        It’s Tindfjallajökull!

        1) The large sulfur spike is about 53.000 years ago, in Greenland.
        2) The Thorsmork ignimbrite, about 200 meters thick ash deposit between Tindfjallajökull and Eyjafjallajokull is dated 54.000 years ago. Several sources around but we have even a blog on it! https://www.volcanocafe.org/an-iceland-enigma-the-thorsmork-ignimbrite/

        3) Torfajokull: you are very good to suspect it too. It did a ring caldera rhyolite big eruption, likely a VEI6, but 70.000 years ago. A good source here: https://davemcgarvie.wordpress.com/2012/05/18/torfajokull-waiting-in-the-shadows-7/
        Surprisingly enough, the 73.000 years ago spike in Greenland could have been originated from this eruption at Torfajokull, rather than Toba. Otherwise, I would suggest that the dating is incorrect and the eruption may actually be more recent (the volcano vigorous geothermal activity could attest to that).

        4) Hofsjokull caldera: surely it was another huge eruption. But there are no studies as far as I am aware of. The eruption thjere must have been at least 30.000 years ago if not a bit older, on the range of 100,000 years ago.

        5) Other less obvious suspects to watch out: Krafla caldera, Askja, Katla… The last two did big eruptions some 10.000-15.000 years ago. Krafla caldera is deeply eroded, so that means it could be older than the ones stated here, so I would guess it’s older than 100.000 years.

        But considering Tindfjallajökull exact match to 53.000 years ago, I would stick to it.

        • Needless to say, Tallis, the evidence for that huge eruption is there. Just book some September holidays to beautiful Thorsmork area, nested between three mighty volcanoes, Tindfjallajokull, Katla and Eyjafjallajokull (ok, this one is a bit less violent than the other two), and the area is just a short hop from other two big ones: Hekla and Torfajokull. The ignimbrites are there.

          Evidence for Torfajokull ring caldera eruption is also there, as it’s a beautiful shaped caldera with plenty geothermal output.

          • I never knew a single word of that eruption, I am completely dumbfounded that I made such a stupid statement despite my incredible intellect!! But seriously I had no idea of that ignimbrite. The eruption must have been HUGE for it to produce something of that size.

          • Tallis, there are a lot of unknown volcanic facts around the world that are awaiting to be discovered.

            Iceland still hides many secrets, but remote areas like Papua or the Altiplano probably hide even more secrets.

            And if consider what lies under the oceans… most underwater calderas are probably not discovered yet. Dring ice ages, the oceans were 100meter below current levels, so probably a fair share of those calderas have been covered and hidden with ocean water.

          • That is part of reason why I will never get bored with volcanoes. It is always good for me to make my mistakes to keep my massive ego in check. I wonder what other secrets (To me at least) the world of volcanology has in store.

        • Just my 2 cents, but I wouldn’t be so quick to just jump to Iceland. We seem to have that tendency on this blog, but there are a lot more enormous calderas in Kamchatka / Iceland that would register highly on the Gisp2 core data. There are also of course some volcanoes closer to the tropics that may qualify as well.

    • Wouldn’t Iceland’s volcanoes have most likely been sub-glacial 53,000 years ago?

        • That’s what I thought.

          Does that not effectively take Iceland out of the running for big sulfur spikes 53,000 years ago in Greenland? Those large eruptions would most certainly have made a mess under the ice sheet, but that same ice sheet would also have severely curtailed (or even eliminated) the subaerial portion of the impact.

          • 53,000 years ago falls into a warmer interlude of the ice age. Not warm by any standards, but not as cold as the depth of the ice age.

  11. And what about ancient supervolcanoes like Glen Coe in Scotland and the Lake Distric volcano in England?

    • Too old to include. It would be very hard to establish eruption sizes for such ancients events. I went for those where there was a fair degree on confidence on scale.

  12. To return to Ulawun.
    After checking, none of the paroxysms caused any stratospheric injection. Maximum recorded column height is 13km.
    So, far the eruption is a hefty VEI-3, next paroxysm will probably move it into the small VEI-4 territory.

    As a comparison, Kelud did 32km for a borderline to VEI-5. Even Sinabung is a more substantial eruption than this and has had columnar heights reaching 15km, and nobody is claiming that to be more than a VEI-4.

    For anyone getting ideas, Mount Hudson in 1991 was the last VEI-5. We are living in a volcanic draught. And do not drag up Cordon Cauliflower, that was not a VEI-5.

  13. M 4.2 – 57km SSE of Pahala, Hawaii

    2019-08-22 14:33:30 (UTC) 18.838°N 155.237°W 46.0 km depth

    That’s Lōʻihi Seamount region. 39 felt reports from across the Big Island even though it was 4:33am there.

  14. M 5.0 – 18km E of Little Lake, CA

    2019-08-22 20:49:50 (UTC) 35.907°N 117.709°W 2.4 km depth

    • Current USGS status https://volcanoes.usgs.gov/volcanoes/coso_volcanic_field/status.html

      Wednesday, July 10, 2019, 10:28 AM PDT (Wednesday, July 10, 2019, 17:28 UTC)

      The intensity of the activity at Coso is gradually declining. Of the approximately 1600 earthquakes detected at M1.0 or above since July 8, only 12 have been M3.0 or above, with the largest two registering M4.1.

      …The current activity at Coso can be considered distant aftershocks, or triggered earthquakes. The M7.1 on July 5 occurred on a NW-trending fault oriented toward the Coso area, and it is common for large earthquakes to cause aftershocks beyond the actual fault rupture. No ground deformation indicative of volcanic activity has been detected, and there is no imminent threat of an eruption. The California Volcano Observatory will continue to monitor the situation for any sign of volcanic activity and provide updates as warranted.

  15. Just in passing, to what degree did the various eruptions have on the fertility of the north american soils? OK, in the arid areas nothing much matters but where there is more rainfall wouldn’t these ash deposits make for excellent soil in due course. Also they seem to be rather readily eroded and would provide a lot of sediment for the far southern river deltas.

    • I live in southwest Washington state. With all the rain we get, and the very fertile soil from the volcanic activity, we can grow just about anything that can survive the cold snaps in the winter.

      • I lived in Pasco Wa. at the time of St.Helens-local media was looking a the farm community .Yes there was griping about the ash, but there was a
        Wine Grape grower from Sicily no less that said on TV. “This like the old country! i love it! Enta provided good soil-so does St. Helens!..”

  16. Here in California, we’ve been seeing distinctly violet colors mixed into the sunsets. The unusual color is attributed to volcanic activity from Raikoke and Ulawun that’s resulting in the Junge Layer becoming somewhat opaque due to aerosol formation. The suspended aerosol scatters blue light, which when combined with the normal red hues of sunset are producing the violet/purple colors.
    http://www.spaceweather.com just had a nice piece on it. Check out the Aug. 22 entry from the archives section for more details.

      • Sadly it’s not just the Amazon. There have been huge fires also in Siberia and recently in Indonesia (where a repeat of the Southeast Asia 2015 haze is feared). We haven’t seen colorful sunsets here in Europe yet.

        I am curious to see how much CO2 have all these fires released into the atmosphere. And how much CO2 capture will be impaired in the next year, due to the massive loss of forest.

        By the way, with the upcoming climate catastrophe, this fits neatly explaining why humans are refusing to acknowledge the severity of the problem:
        https://en.wikipedia.org/wiki/Normalcy_bias

          • Hmmm, 2019 is the worst fire season on record for the Amazon.
            Too many links to post….just do a quick search for Amazon Fires and you’ll see what’s going on.
            Warning: It’s not pretty.
            Warning: While I can’t confirm scientifically, news media is constantly mentioning that the Amazon is the source of 20% of the planets’ oxygen.
            Now here’s something to consider: If we lower the oxygen level by 20%, then our fire rates should drop dramatically. (no oxygen=no oxidation=no combustion). Sounds like a line of logic only the leaders of the most powerful nations on earth could accept.

      • Perhaps….but smoke particles generally do not scatter blue light, but rather adsorb it.
        Here in the northern Sacramento Valley, I am unfortunately WAYYY too familiar with fire-borne sunsets, and violet is not one of the colors we see.
        Secondly, independent of Hadley Cell activity/flow, unless you have a monstrous storm with towers reaching into/above the tropopause, then there isn’t enough vertical transport of smoke that gets into the aerosol/Junge Layer. If there was a hurricane immediately off the west coast of SA that was tapping into the smoke, it might be different (hurricanes are long known as the sources of sea-salts that get transported into the stratosphere which make up a good fraction of “natural” aerosol formation)….but, the equatorial tropics have been unusually quiet this season (so far), so I don’t believe the ambient weather conditions are making an appreciable impact on the smoke’s northward dispersion.
        Thirdly, smoke has a relatively short lifetime in the atmosphere and easily washes out of the air at lower elevations….especially in the tropics where frequent showers/storms are present.
        And lastly, the upper air flow is currently not favorable for transporting Amazon smoke north of the Equator. This time of year the northern edge of the ITCZ (Inter Tropical Convergence Zone which straddles the Equator +/- 5 to 10 degrees) is quite active, with a strong E-W flow in the upper layers in northern hemisphere and a weaker W-E flow in the southern hemisphere. As a result, the mean flow over the fire should be pushing the bulk of the smoke out over the Pacific, so I would suspect that the vast majority of Amazon smoke is getting washed out long before it gets into the stratosphere.
        Anyway, that’s my take…..and admittedly I could be “all wet” in my analysis…..but fer now I’m going with the “volcanic” explanation for the violet sunsets we’ve been seeing in the middle latitudes.

        • Also in California. It’s August and my cat still has his winter coat.
          There is definitely some haze, the sky is a paler blue this last few weeks, but I am near the coast and you can’t tell if it’s just water vapor by looking at it.

  17. Does anybody know where to find gisp2 ice core volcanic so2 data? I used to be able to find it here ftp://ftp.ncdc.noaa.gov/pub/data/paleo/climate_forcing/volcanic_aerosols/gisp2_volcanic_markers.txt , but apparently that page was taken down for some reason.

    I had that page bookmarked for some time since it was the best non-paywalled reference for volcanic ice core data I could find.

    Also, RE: the 54,000 bc So2 spike, I still think we need to focus more on WTF happened with the so2 spikes roughly 13000 years ago. Those made anything in the Holocene look miniscule by comparison, yet I never see anyone trying to tie these to a mystery eruption. Based on the so2 sample, these eruptions should have been enormous, or just enormously gassy, yet there isn’t anything to show for them.

    • Try this.

      “This file contains the volcanic sulfate record in the GISP2 core on the
      Meese/Sowers timescale. Each sample is approximately bi-annual for the last ~12,000 years with a consistent increase in the time covered by each sample to around 50 years/sample at 110,000 years ago. The volcanic sulfate record is derived by applying an empirical orthogonal function (EOF) analysis on the entire glaciochemical time series (Mayewski et al., 1997a).”

      ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/chem/volcano.txt

      Don’t forget that there is an impact event somewhere in that data.

      https://earthsky.org/earth/meteorite-crater-under-greenland-ice

      And evidently, another may have been found.

      https://earthsky.org/earth/another-huge-impact-crater-under-greenland-ice

      GISP2 is probably about 1500+ km from the claimed impactor areas. I also have no idea if there is sulfate bearing rock in the crater areas. There is no definative age for the first crater discovered… “less that 3 million years ago” per the article, and probably 12,000 ybp according to others. Whether or not the Hiawatha crater is connected to the “Black Mat” theory has yet to be seen.

      My point is that there could be tainted data in that timeframe.

    • I do not think we have a problem really to tie that to something.
      That is when Iceland went bonkers as the glacial ice left.

      Basically you had all of the big hitters going off at almost the same time (geologically speaking), chief among them the 50km3 Theistareykjarbunga eruption. But, most of the shields was constructed at the same time, together with large eruptions at Krafla, Fremrinamur, Herdubreid and Askja. The list really just goes on for volcanoes that went bonkers around 13000 years ago in Iceland.

      I think even Jesper would have been satisfied watching that, cider and popcorn at hand. 🙂

      • Theistareykjarbunga, Trölladyngja, Skaldbreidur was pretty much Icelands own Puu Oo s.
        Looooong slow pahoehoe tube / lake feed eruptions lasting for more than a 100 years.

        Carl did you know that pahoehoe is acually the most common lava flow surface in Iceland.
        Souch flows covers almost whole North rift zone.
        It strongly says that Iceland does slow, long lived fluid activity sometimes.
        Souch Iceland activity can last a long time decades/ perhaps centruries and cover huge areas with slow pahoehoe.

        But I also enjoys the large fast flood lavas
        And large Basaltic Plinian eruptions.
        Now back to Big explosive events …

      • Theistareykjarbunga was basicaly an Erta Ale
        A fast growing pahoehoe shield that was more or less constantly active lava flows during the more than 100 years? it was going.

        Iceland went bonkers because of decompressing melting after the Ice dissapeared
        This caused the shields to form and the Lava Floods and the VEI 6 s to appear in a short spike
        9000 to 8000 years ago

    • How does floating pumice form underwater? I mean, how does the air get in there?

      • Gas coming out of solution from the magma. CO2, SO2 etc. Not really what would be considered “air” as we know it.

        • Coming out of solution due to pressure and temperature changes?
          would have thought the interaction with water would get in the way of that.
          interesting. maybe not all the magma actually “touches” the water.

  18. Carl question
    Is there any explosive Icelandic eruption that coud make it to this article eruption list here?
    I knows that a single 100 s of km3 tephra is very unlikley in Icelands thin crusted setting.
    But Katlas more than 10 km wide and 100 s meters deep caldera probaly formed during a major explosive event?
    Any VEI 7 Icelandic tephra event?
    Sakursunarvatn is the closest but thats 5 VEI 6 events
    What formed Askjas outer caldera thats now filled with lava flows.

    • The closest to a VEI-7 that we know about is the largest of the five Saksunarvatn eruptions.
      There might be two culprits that might have done small VEI-7s during the last glacial period. But nothing is proven and to be honest, are mostly feverish fantasies.
      If, and this is an if on a supertanker scale, any have done it, the only viable candidates are Tindfjallajökull and Torfajökull.
      Let us say that the chance that Iceland ever did it, is about 10 percent or less. There is just no ash layer of sufficient thickness anywhere.

      Saksunarvatn was 3 VEI-6 and 2 VEI-5 to be correct.

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