The Toba Supereruption

Panorama of Lake Toba (https://en.wikipedia.org/wiki/Lake_Toba)

Panorama of Lake Toba (https://en.wikipedia.org/wiki/Lake_Toba)

Lake Toba is a beautiful place. The largest and deepest lake in Southeast Asia, it contains an island (Samosir) almost the size of Singapore – the fifth largest lake island in the world, and the largest island-within-an-island. Samosir contains two smaller lakes, Lake Sidihoni and Lake Aek Natonang – the former even contains its own island. The best views of Lake Toba and Samosir, in the highlands of Northern Sumatra, are from Tele. Most tourists end up on the TukTuk peninsula. The tourist blurb calls it a place ‘to sit back, relax, and absorb’, and ‘a beautiful place to do nothing at all’. But this tranquility hides a violent secret. Lake Toba is the place of the largest volcanic eruption on Earth of the past 2 million years.

(https://tobaexplorer.wordpress.com/)

(https://tobaexplorer.wordpress.com/)

The lake is 100 by 30 km in size, has a surface area of 1100 km2, and a water volume of 240 km3. It is up to 450 m deep. The volume makes it the 24th largest lake in the world (admittedly this list excludes the Caspian Sea), and bigger than the Dead Sea. The full extent traces a caldera with a staggering size. Toba, together with Yellowstone, Long Valley, Valles Caldera, Taupo Volcano, and Aira Caldera, is one of the ‘secret six’: the current supervolcanoes. (But Aira seems too small for this list!) Of these six, Toba is the most densely populated. Samosir, the centre of the massive Toba caldera, is home to more than 300,000 people. In contrast, the town of Taupo only has a population of 25,000. The term ‘supervolcano’ was first introduced to describe Toba. It is now defined as a volcano capable of ejecting over 1000 km3. Since Toba, only the Taupo Oruanui eruption in New Zealand (26,500 years ago, 530 km3 DRE) has come close.

The region of lake Toba has suffered four major eruptions, starting 1.2 million years ago from a large strato-volcano at the northwest end of Lake Toba (35 km3 DRE), than 840,000 years ago towards the south of Lake Toba (500 km3 DRE, possibly more), 500,000 years ago at the northern end of the lake (80 km3 DRE), and the fourth and final eruption occurred 74,200 +- 900 years ago from multiple locations, perhaps the entire surrounding ring fracture (2800 km3 DRE). The eruptions are named after the tuff layers they produced: the Haranggoal dacite tuff (HDT), the oldest (OTT), the middle (MTT), and the youngest Toba tuff (YTT). (The naming lost some of its logic when a layer older than the oldest was found.) The first three all created calderas, but the final eruption was much larger and its caldera encompasses the earlier three. Nowadays the region is considered inactive, but the volcanic roots are still apparent in the hot (or even very hot) springs, on the west of the island. (Hot springs seem a fairly common occurrence in supervolcanoes.) There is on-going activity in the wider area: Mount Sinabung is only 40km from the edge of the lake.

 

Toba from space

Toba from space

Lava (or rather, tuff) from the YTT eruption covers an area of more than 20,000 km2 with a typical thickness of 50 meter (but up to 400 meter in some places and more than 600 meter inside the caldera); the flows reached the ocean on both sides of Sumatra. The lack of ash at the bottom of the lava indicates that there was no plinian phase at the start of the eruption: there was fountaining probably to great height but but no large explosions, and the velocities were on the low side. The distant flows came from silica-rich part of the magma chamber, while the deeper silica-poor magma mainly filled the caldera and was probably erupted while the caldera collapse was in progress.

The distant ash blanket from Toba covers an area estimated at 7 million square kilometre (close to the area of the US) and has been found as far away as the Arabian Sea and Lake Malawi. A lot ended up in the Indian ocean. The average thickness of the ash layer is 10 cm, but in Malaysia, 350 km away, it averages 90 cm and is up to 3 meter in places, and in India, 3100 km away, a thickness of 50cm – 1m is common and in one place a thickness up to 6 meter has been reported. The thickest layers were probably concentrated by rivers. The ash shows two layers: the lower one is coarse-grained and the upper one more fine-grained unit. The lower layer is not seen in the more distant locations. This suggests that the ash was produced in two phases. The total volume of the ash corresponds to 800 km3 DRE.

The features of the Toba Caldera. Caldera formed by the Younger Toba Tuff eruption (YTT), Middle Toba Tuff (MTT),  Older Toba Tuff eruption (OTT) and Haranggaoal (HDT) (frontiersin.org)

The features of the Toba Caldera. Caldera formed by the Younger Toba Tuff eruption (YTT), Middle Toba Tuff (MTT), Older Toba Tuff eruption (OTT) and Haranggaoal (HDT) (frontiersin.org)

The dispersion of the ash shows that the eruption took place during the monsoon season, in the northern summer. The winds at that time blow towards India. A winter eruption would have deposited the ash further south. The duration of the eruption is only known approximately, from the structure of the ash layers in the ocean at different depths. This has shown that the ash producing phase lasted between 9 and 14 days. For comparison, the main eruptions of Tambora and Krakatoa both lasted 24 hours, although Krakatoa also had a lesser eruption for the preceding 4 months.

Toba erupted a volume estimated at 2800 km3 DRE, including about 1000 km3 of lava. Imagine this: Bardarbunga took 6 months to erupt 1 km3. Laki, while suffocating Iceland, erupted 1 km3 every two weeks. Toba erupted this much every 10 minutes! Its eruption rate was ten times faster even than that of Tambora.

The eruption

Putting this together, we can get a rough idea how the eruption proceeded. The huge magma chamber was located some 10 km below the surface. It had been present for 150,000 years, and during this time crystallization had occurred. The crystals sank to deeper levels, leaving the upper part of reservoir silica-rich and the bottom silica-poor and crystal-rich. Eventually, the heat began to weaken and melt the roof of the magma chamber, and buoyancy of the magma pushed up the roof, until eventually it started to crack. Once the melt fraction reaches 50%, the overpressure of a huge magma chamber can spontaneously crack 10km of rock: unlike normal eruptions, supervolcanoes do not need a new influx of magma to initiate an eruption. The cracking may have been preceded by major inflation (perhaps hundreds of meters, albeit over a long time), and finally caused big earthquakes. In Krakatoa, a big earthquake happened three years before the eruption.

The first crack provided a small outlet for the first lava. As magma escaped, the changing pressure below caused more cracks and the eruption rapidly intensified. Lava began to come from other places along the ring fracture, and finally, sometime in July or August, along the entire ring. It is a guess how long this initial phase would have lasted; for Krakatoa, it took several months. There was probably no central eruption: all came from the caldera ring. As has been pointed out in this blog, very large eruptions can have multiple exit points simultaneously. The lava now fountained out at incredible rates, dwarfing anything the world has seen since. Fountain collapse, mostly during the early and middle part of the eruption, gave rise to pyroclastic flows traveling hundreds of kilometers. The lava and tuff eventually covered the width of Sumatra to a depth of 50 meters or more. The cliffs around the lake, 300 meters high, were also created from these. There may have been one or more very large explosions at this time, with an eruption column tens of kilometer high and depositing ash across many parts of the Indian ocean, but perhaps not reaching India. However, this is disputed: some people see little or no evidence for such high eruption columns and think all the lava was erupted at low velocity.

The heat of the pyroclastic flows propelled smaller ash particles into the air, up to 10 kilometer high (these are called secondary or co-ignimbrite plumes, and are known from Mt St Helens). This ash traveled far and wide, following the trade winds, and blanketed nearby Malaysia but also India. Most of the ash came from this.

Eventually the magma reservoir had lost so much pressure that the ridge began a rapid collapse, within days to weeks forming a hole 2 kilometer deep. As the caldera collapsed deeper the eruption began to wane and the ejecta now stayed mostly within the caldera. By this time, the magma came from the bottom of the original reservoir which had grown silica-poor. The eruption finally ended with a whimper.

The volcano now remained quiet for a very long time. Perhaps 40,000 years after the eruption, the magma reservoir began to refill and the centre of the caldera began to inflate. Very small eruptions occurred, mainly along the ring fault, mostly from old magma remnants but in one or two cases new magma also (just) made it to the surface and formed some cones. The rise became a resurgent dome, formed an island, and is now called Samosir. It has risen by some 1100 meters. The large magma chamber underneath very closely follows the contours of Samosir. There is another, smaller magma chamber to the north, partly underneath the lake and partly west of the caldera. Samosir is no longer rising.

(Wendy Bohrson)

(Wendy Bohrson)

Why did Toba become a supervolcano?

Why did Toba become so large? This is not really known: something must have allowed a very large magma reservoir to build up, relatively close to the surface. Once you get a very large, single reservoir, it can force an eruption through slow pressure. Small reservoirs, often divided into honeycomb chambers do not do this. It has been argued that volcanoes can slowly develop these huge chambers as they grow old, so that all it takes is a constant, slow magma supply over very long periods. But at the same time, the new magma should enlarge the reservoir rather than erupting at the surface. In the case of Toba, we can make a guess what may have caused this.

Albert Toba Sumatran Fault

All Indonesian volcanoes, including Toba, are fed by subduction, and not by a hotspot. Unusually, the Sumatran volcanoes are also located very close to a fault. The Sumatra fault runs along the entire length of the island, including the western edge of the Toba caldera. This fault runs parallel to the off-shore Sunda megathrust fault (the location of the 2004 earthquake), where the Indian-Australian plate subducts underneath the South-East Asian plate. In Sumatra, this subduction occurs not perpendicular to the faults, but at an angle: while the plate slides underneath, it also moves to the side, northward. Some of this slip motion occurs along the Sumatra fault. This can in fact be seen in the YTT ejecta: on either side of the fault, they are displaced by 2 km. The fault must therefore be moving at 2.7 cm per year. The slip is faster to the northwest of Toba than it is in the south. This causes a problem, as over time a gap is created. This currently happens just south of Lake Toba. The close association of a fault and a volcanic arc in Sumatra is unusual and may even be a coincidence. But this thinning of the crust could be one reason for the very large magma reservoir underneath Toba: it continuously creates space (or a region of reducing pressure) for the magma to move into.

 

The aftermath

The effects of the eruption are often discussed but not that well known. Certainly, much of Sumatra would have been covered by lava, poisoned by gases, and sterilized by pyroclastic heat – a hell worthy of Dante. The ash would have wiped out most life to the west and northwest, luckily largely oceanic regions but including Malaysia and part of India. Other places were spared, such as Indonesia further to the east and the Philippines, due to the luck of the prevailing winds. The effect on humanity is not clear. If air travel had been discovered by than, it would have had to be abandoned for perhaps years. But that would have been the least of their worries, as it is argued that most of the emerging Homo Sapiens were killed off, leaving only a few thousand people to populate the world. There is some genetic evidence for such a bottle neck. However, it is not known whether this bottle neck coincided with Toba. In India, a few stone tools below the Toba ash are similar to the (many more) tools above it, suggesting that the culture survived – even if the local population did not. The Earth’s climate and the monsoon would have been shot for years to decades, and famine inevitable, but the amount of global cooling depends on the amount of sulphur which was ejected which is very uncertain. Cooling of between 1 and 6C has been estimated but different authors.

Were the climatic consequences even worse? The eruption happened almost exactly at the onset of a deep glacial period lasting 1000 years. Toba could not have caused this by itself: remember that volcanoes cause cool summers but not cold winters. But Toba could have caused a change in the ocean currents. This may have pushed the Earth over the brink into a new but short-lived ice age. This is pretty speculative but not impossible; however the ‘Toba catastrophe theory’ contains a fair amount of hyperbole. But if this event had happened in the modern era, it would indeed have been catastrophic. The casualties would not have been counted in the millions, but in hundreds of millions. Our society is not resilient to a Toba-sized event.

Prospects

Luckily, eruptions the size of Toba are expected only about once every million years. A low VEI8 (as in Taupo) may occur every 100,000 years. A low VEI7 may happen once a century or so. From the point of risk management, we should be prepared for one-in-ten-thousand-year events. That corresponds to roughly a medium VEI7, of 100 km3 DRE. Toba was completely off this scale.

The black dots show volcanoes (black dots) that have produced eruptions of more than 150 km3 of magma within the last million years (S. Self). Note that Europe and North America are not immune. Click if you dare.

The black dots show volcanoes (black dots) that have produced eruptions of more than 150 km3 of magma within the last million years (S. Self). Note that Europe and North America are not immune. Click if you dare. http://rsta.royalsocietypublishing.org/content/roypta/364/1845/2073/F1.large.jpg

 

The risk of another large eruption from Toba is currently extremely small. The repose times have been fairly consistent around 400,000 years, and the next one is therefore not due until around AD 300,000 (but the sizes of the eruption are highly variable and unpredictable, and do not always reach the defined limit for supervolcano size). AD 300,000 is a very long time away! Yellowstone has even longer repose times than Toba (600,000 years on average), and Valles Caldera is similar to Toba at 335,000 years. Supervolcanoes do it more than once, but not frequent.

Another way to look at this is by using average eruption rates. Averaged over millennia, oceanic arc volcanoes erupt typically 0.002-0.005 km3 per year. Toba’s average rate is 0.005 km3 per year. It became a supervolcano not because it produces magma faster than normal volcanoes, but because its magma chamber has a much larger storage capacity which can cope with the long times between eruptions. The road to destruction is traveled slowly.

Lake Toba is a tranquil place, far from the hustle of modern life. But what a past.

Albert Toba tuktuk

Small business in Tuktuk Siadong, Tuktuk Peninsula, Samosir Island (https://tobaexplorer.wordpress.com/ )

 

Albert

150 thoughts on “The Toba Supereruption

  1. Albert, what was the source of that graphic at the bottom? Would be interesting to look through the volcanoes that are labeled, although it’s surely missing quite a few large-eruptors.

    Good post overall! Surprised there hasn’t been a comprehensive toba post here before.

    One thing –

    “Toba, together with Yellowstone, Long Valley, Valles Caldera, Taupo Volcano, and Aira Caldera, is one of the ‘secret six’: the current supervolcanoes.”

    Aira, as you mention is definitely too small at this point to compare to Toba or Yellowstone. Similarly, Valles and Long valley are also not that much larger than Aira. Where did this “secret six” name come from? It’s not really that accurate to compare these six volcanoes to each other, and if we were to include Long Valley, Aira, and Valles, the “secret six” should probably be renamed the “secret fifty” since there are many volcanoes around the world that are similar in size to these systems. Not to nitpick, but this could be misleading for those who are newer to studying volcanoes and past large eruptions.

  2. Also, slightly unrelated, but the explanation of why Toba became a supervolcano is essentially a shortened version of why I expect the Klyuchevskoi volcanic group in Kamchatka to become a supervolcano at some point in the geological future (long after I’m dead).

  3. Great post, Albert 🙂

    Is there any link, apart from the Great Sumatra Fault and the subduction zone, between Toba and Sinabung; and, what are the odds that Sinabung will go the same way in the dim and distant future?

  4. To answer some of the questions

    The last picture came from https://tobaexplorer.wordpress.com/ Perhaps a knowledgeable dragon/sheep can add this to the post?

    There is no indication that the magma chambers of Toba (two, currently) and Sinabung are linked. Where Sinabung will eventually do a Toba: who knows. The eruptions in Toba moved back and forth by ~100 km, so 40 km seems surmountable. But the main magma chamber is nowadays under Samosir: for Sinabung to do this, it probably should build up its own large chamber. I would think that at the moment, it is too young a volcano for this. But the first eruption from Toba was ‘only’ VEI7 and may have come from a stratovolcano similar to Sinabung. However, note that while Indonesia holds 2/3rd of all recorded volcanic casualties, the ‘super’ eruptions are spread out much more equally. This suggests supervolcanoes need a lot of space to grow.

    The list of ‘secret six’ (my name) first came from I think of National Geographic or the Discovery Channel and it resurfaces regularly in catastrophe websites. I share the doubts expressed about this list. It must be possible to come up with a more authorative one! Long Valley may have potential (perhaps someone would like to write on it?)

    The explanation for why Toba grew so large developed from a paper on the difference between volcanoes in ‘extensional’ and in ‘compressive’ settings. Toba seemed an extreme version of the former. Yes, Kamchatka shares some characteristics.

  5. Thanks for covering this eruption. Who knew that Toba did not have a traditional explosion at the onset of this event. The lake is gigantic. From pictures that are of posted of the location it is really hard to believe that a volcano is located underneath.

    Since Sinabung is not located to far, this current eruption is getting scarier by the day in my opinion.

    Going to Columbia now, an eruption at Nevada del Ruiz is on the way? I would imagine that she is monitored since many of us know what happened there last time.

  6. ok, minor confusion going on in my head

    https://en.wikipedia.org/wiki/Tuff
    says Tuff (from the Italian tufo) is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is compacted into a solid rock in a process called consolidation.

    but your post says
    Lava (or rather, tuff) from the YTT eruption covers an area of more than 20,000 km2 with a typical thickness of 50 meter (but up to 400 meter in some places and more than 600 meter inside the caldera); the flows reached the ocean on both sides of Sumatra. The lack of ash at the bottom of the lava.

    lack of ash would be lack of tuff (as tuff is ash) – are we talking pyroclastic flows rather than lava flows ?

      • thanks KarenZ that let me get through the rest of the article – I think some more clarification by albert would be cool though 🙂

        • I was equally confused! Different papers said it was lava flows or tuff flows. I finally figured out that the older papers stated it as lava and the more recent ones as tuff. The picture I have is that of lava fountains kilometers high. The lava partly solidifies in the air, and comes down as a mix of ash and lava bombs. If anyone knows more about this than I do (not a geologist!), please enlighten us!

          • It may be relevant to note that when welded ignimbrites were first described, before their origin was understood, they were sometimes described as rhyolite lava sheets – because they superficially look like lava flows- ; possibly what is going on here?

    • I don’t know if this helps in visualising what happened, but first, think of a volcano as an inverted rocket engine (and remember Newton’s Third Law; every action has an equal and opposite reaction). Now the bigger the rocket, the greater the thrust or height of the eruption column, right? But this only applies to regular volcanoes constrained by an edifice and a vent at or near the top!

      With these large caldera volcanoes, an eruption begins at the edges of the plate overlying the magma chamber, either because inflation or deflation produces “circular” fractures. Initially, you will have several constrained vents ejecting magma at high pressure high into the atmosphere. You will not have a single vent with a Mastin-calculated height of 80 – 100 km! You will have maybe ten or several tens of vents producing 20 – 30 km high eruption columns (plus a multitude of smaller ones) accompanied by prodigious base surges.

      Once the most volatile magma containing the greatest amount of volcanic gasses has been vented off, the caldera has truly become unzipped and the slab on top (20 x 40 km oval + 5 km thick = 4,000 cubic km) presses down on the magma below which oozes through the ring fracture. It still contains enough volcanic gases to erupt as ash and not lava, but ash very dense and very hot. You have your ignimbrite-forming pyroclastic base surge here.

      Because there’s so comparatively little gas, it does not travel the proverbial millions of miles to spread all over Earth but rather just a mere 100 km or so. Being so dense and so hot, once the gases contained have “evaporated” the ejected magma, still at temperatures as high as 800-900C over a large area, solidifies and fuses to become a tuff, welded or non-welded depending upon how gas rich it was to begin with – the greater the gas content, the higher it erupts and thus cools more before settling down. If you want to, compare it to a pot of fudge boiling over.

        • Lava is generally defined as magma that has been erupted out of a volcano. So I believe the confusion lies in the fact that a tuff is a way to describe lava that has been extruded as pyroclastic flows and ashfall.

          • I always think of lava as being anything that oozes as opposed to tephra being anything that is clastic, both of which were magma – never really thought of tephra as a subset of lava, if it is then I want a word for lava that is not tephra

      • Yes, that it correct. The height also depends on the size of the exit hole. At the same amount of pressure, a smaller hole will give a higher fountain (try this with a garden hose). In Bardarbunga, the jets initially were high, but once a lava lake formed above the exit hole, the ‘hole’ became the size of the lake and the fountains stayed much lower.

        The indications are that the eruption column was less than 10 kilometer high but several kilometer high fountains is likely. Any time such a fountain stops (or stutters) you are going to get pyroclastic flows. These would have formed the enormous sheets on Sumatra. Note the superficial similarity between welded ignimbrite and lava sheets which Michael mentions above.

        • That’s not always true, it depends on the viscosity and pipe diameter. What you have is a pressure difference across a pipe. As the pipe diameter goes up the flow for any given pressure goes up more than proportionally equally as the viscosity.

          I doubt a volcano is like a water hose. That implies a very large hose diameter and a small orifice, whilst I suspect a volcano is more like an open pipe all of the (roughly) same diameter.

          I deleted a previous post where I did some assessments for the pipe between the reservoir and the surface. I used standard tables but for some unaccountable reason (!) it did not extend very well to the pressures and flows of a volcano.

          Note that I am well known for losing zeros and being out by factors of 10… or more.

          Firstly some initial assumptions:

          1) Assume viscosity close to that of ketchup (ie a very hot basaltic lava). 2 poise or 0.2 kg/m-s
          http://www.gso.uri.edu/lava/MagmaProperties/properties.html

          2) Assume velocity in the pipe is such as to deliver a ballistic (ie non-thermally augmented) velocity to fire large bombs to an altitude of 2km. This equates to a pipe velocity of circa 200m/s.

          3) Now we have to find the Reynolds number for the system.
          https://en.wikipedia.org/wiki/Reynolds_number

          3.1) Initially assume a pipe diameter equivalent to a circular tube of 2m. Technically this is 4x the area of the tube divided by the wetted perimeter of the pipe. For a very wide crack thus equates to twice the gap, or 1m. To give us Dh =2.

          3.2) So assume:
          Dh = 2 (see 3.1)
          v = 200 m/s (see 2)
          r = 4000 kg/m^3 (density)
          k = 0.2 kg/m-s (see 1)

          So Re = r v Dh/k = 4000 x 200 x 2/0.2 = 8 x 10^6

          4) Next we need to find the friction factor for the system:

          Guessing the roughness is tricky. Lets assume that the walls of the pipe are semi-molten and so smooth except for some small surface ripples, perhaps similar to an old sewer, say 5mm for a pipe diameter/crack say 1000mm this equates to a ‘roughness’ of 0.005 giving a friction factor of Ff=0.03.

          5) Now we can calculate the pressure drop per meter
          https://en.wikipedia.org/wiki/Darcy–Weisbach_equation

          dP = Ff r v^2 L/2Dh = 0.03 x 4000 x 200×200 x1 / (2×2) = 1,200,000 Pascals = 12 bar.

          Or 12kbar per km. Which is a tad high!

          6) Of course we wouldn’t expect a gas-free high volume eruption to produce 2km fountains, and if gassy the density and viscosity will be significantly lower. Lets try again with Dh=10m, k=0.1 and r=2000 (ie 50% by volume gas on average).

          Re= 2000 x 200 x 10 /0.1 = 40 x 10^6
          Ff = 0.03,
          no change, in retrospect thats just what the curve suggests. For high Reynolds numbers the effective flow just sticks. With a factor 2 on density and 5 on diameter its 1/10th the pressure.
          dP= 0.03 x 2000 x 200×200 x 1/(2×10) = 120,000 Pascals = 1.2 bar/m

          7) 1.2 bar/m is definitely in the right order. Take a reservoir at 5km the hydrostatic pressure is likely to be circa 20kbar and the required pressure from (6) indicates 6kbar is required, plenty left in hand without even requiring a pre-pressurised chamber. Gas precipitation in the mix is quite enough to power a very significant eruption once it gets started,

          8) I think one thing to note is that even a 2m conduit will not produce enough flow to generate a significant eruption, something approaching 10m is required. Its also worth noting that the internal pipework needs to be either narrow and short to the main vent or large diameter and near for a significant event. Otherwise a short eruption will occur before the supplies close enough to the main vent become exhausted and ther eruption fail to maintain itself because flow to the vent cannot keep up.

          Worth some comment, I think?

          released after being put on hold by spam checker

          • The only thing I have to toss in here is that Basalt is about 3100 kg/m³, Granite is about 2700 kg/m³. Dunno how that works out as a melt phase.

            A 10 km plume height (ash) equates to a mass ejection rate of about 794.9 m³/s DRE. (using Mastin et al)

            At some point in the vent, gas will begin to nucleate and start to reduce the lithostatic pressure of the vent pipe, similar to the way that a well “kick” reduces the pressure gradient of the fluid in a drill column as formations fluids (and dissolved gases) push into the well bore. As the condition progresses, the system can enter a runaway phase and get quite energetic.

            Yes, I realize that you specified a gas free magma, but its something that should at least stay in the back of the mind while considering this.

          • nice calculating work there – if you take that model and a known vent size, and suspected magma chamber depth, does that let someone work out the lithostatic pressure required to constrain an eruption – and can that be used to ‘predict’ anything?

          • Thank you for your reply, geolurking.

            Lots of things needed looking out and double checking and expanding but I had no time to do it in a reasonable period.

            It looks like gas free lava would not easily produce the flow through the orifice to give the required 2km fountain.First calc. Other scenarios would.

            200m/s with a vent area of 30m^2 is more like 6000 m^3/s or 3000 removing gas so much larger but in the right ball park. I don’t think the density errors are very significant.

            The second calc, which worked rather better was a guestimate with 50% gas.

            Frankly I’m quite surprised how much useful stuff can be produced using simple fluid dynamics which nobody seems to have done.

          • The highest reported lava fountains which I have seen is by a certain Boris Behncke, on Etna. It mentions fountains 800 meters high. The gas content must be the main driving force, I guess. The buoyancy of the magma does help: even if you turn the pressure off, the stuff keeps rising, unlike water.

          • A few quick comments on the calculation: The velocity inside the pipe is probably quite different at different depth. The flow rate should be the same: velocity*cross section/density is constant. But the cross section is self regulated: the magma itself pushes the sides of the channel out. The velocity in the conduit may thus be quite a bit smaller.

            The viscosity may vary enormously along the flow, by more than 5 orders of magnitude. Your value is for very hot stuff. At conduit temperatures, it could be more like 10^5. That makes the Reynold number low (subsonic flow). I would guess that you number on the pressure drop is reasonable, maybe within a factor of 10. But the big uncertainty is, as you mention, the gas bubbles in the rising magma. Like mixing the ketchup with pepsi and put it inside a shaker. It is a confined explosion and the only way out is up. The pressure of the developing gas drives the fountains.

            Volcanophysics is hard.

      • It’s a matter of vent size and distribution as you say; with a constrained vent, you get dramatically high ultraplinian plumes. If the vent(s) are larger and less constrained, you get less energy directed vertically, and more of a ‘boil over’ style of eruption, with PDCs surging in all directions, a little like dry ice producing CO2 which boils over the edge of a beaker.

        Mt. Lamington is a classic example of this, and illustrated why these can be much more dangerous and deadly in human terms than a predominantly vertical blast; they are frequently called Lamington-style eruptions.

  7. An addendum from a post I did a while back. Just the nuts and bolts. Following a stratospheric injection of SO2, it takes about 2 months for that load to become Sulfate and make a peak in the stratospheric aerosol layer (Junge Layer). Once this happens, the layer will remain pretty consistent until it sediments out after about 50 months.

    A very impressive post Albert, a most enjoyable read. 😀


    … and the California drought continues…

    “From the half-million acres of parched and idle farmland to the swaths of receding reservoirs, the signs of California’s historic drought are obvious. “

    • Saturday evening in Fresno it rained .36 inches.

      This might not sound like much, but it set a new record for the entire month of July.

      Was sitting on the back porch at a friend’s house that night watching a lightning show to the west that wasn’t moving. Got on my weather app and watched a huge thunderstorm sit still for an hour and a half, all oranges and reds on the radar. They got almost 2 inches out there. Hundreds of almond trees fell over.

    • Yes every now and then (particularly when a Nino is cooking) TS and Hurricane remnants make it in to So Cal. I was in Stockton -got hit by one. Put the fires out ..
      We went back to Oregon-which is what we wanted…

    • ” Vertical rates on average exceed 15 mm/yr and may indicate glacio-isostatic adjustment. Nevertheless, colocated GPS and dry tilt in the center of the caldera indicate subsidence at up to 10 mm/yr. ”

      Abstract → Deformation of Torfajokull Caldera, Iceland Scheiber, S. C.; Lafemina, P.; Sturkell, E. 2007AGUFM.V31F..03S

      • That is troubling to think of the
        Subsidence there and they bring Hekla into the study as well. Wondering why?

        • No idea. Other than being a neighbor.

          However, there was that bit of magma that seemed to flow out from under Hekla and down towards the plain to the south. It may have moved off towards the NE if I remember correctly, but I didn’t have enough GPS to indicate which way it actually went after it moved south.

          (Carl had me look for it after he noticed an odd deflation for Hekla.)

  8. do you think oblique subduction might lead to an elongated magma ‘chamber’ – a small connected series along the fault line orientation ?? might that explain a large chamber but no one spot having got large enough to erupt ?

    • I would certainly think that it started out as a series of magma chambers. Over time they melted the walls and merged. But you need to keep it from erupting at every stage of the process, first when the chambers are small, than when they grow larger. I am picturing as a drip-feed, never a large sudden influx of new magma but just very slow growth. The gap created by the different slip along the fault keeps the pressure down while the drip continues. That leaves only the buoyancy force of the magma, but that doesn’t become strong enough to crack the roof until the chamber has grown enormous, with a high melt fraction. I think there is room for more research here!

      • One way to keep it from erupting too often and in too-large quantities would be to keep it gas-poor. If you pump juvenile magma into bedrock (which has once already solidified and gotten rid of the gas content), the remelted bedrock magma will be gas poor and thus “non-eruptible” while still containing vast amounts of energy in the forms of heat, pressure and inter-crystal bondings.

    • Based on what I know, and what has been studied, I would say it’s a combination of a deeper (than normal) magma chamber along with magma that is brought from an uneruptible state into an eruptible state within a considerably short period of time.

      The biggest thing to understand here is that most of the magma that comes from volcanic systems like these is simply melted bedrock. Now, every volcano in an arc system melts bedrock to some degree, but you need a truly massive heat source to melt the volume of rock in order to get what you see at toba. As has been discussed, this come from a combination of extensional tectonics, and subduction magmatism.

      Once you get that prolific heat source, what comes next is massive under-plating, which occurs when voluminous amounts of fresh magma sit below the bottom of the crust at about 20km depth (depending on crustal thickness), heating it up slowly and melting it. This is what is the source of the Taupo Volcanic zone, and likely the same is the case here at Toba. The reason it doesn’t erupt super quick is because it’s deeper than a normal magma chamber, being the result of melted underplating. As mentioned, the inability to blow off steam results in enormous magma chambers. Now, if this occurred in a region without thin crust, an eruption may never happen since the overlying 40km thick sheet of bedrock would be enough to keep it in check. But in an area of extremely thin crust, it makes sense that an enormous batch of melted rock could override the strength of the overlying crust. In some ways, it wouldn’t be unreasonable to think of supervolcanoes as batholiths that reach too close to the surface, and blow out (although that’s not entirely accurate).

      In a normal volcano that isn’t in a region of crustal thinning, this wouldn’t rupture since the strength of the overlying rock is enough to hold it in, but these aren’t normal volcanoes, and the wider the area you get, the weaker the overlying structure becomes.

      So how does it get erupted?

      This rock can be kept in uneruptible states for extremely long periods of time, but a fresh basalt injection into the crust can heat it up to an eruptible level pretty fast. If it gets hot enough, it will remobilize, and start mixing with the basalt injection. The problem in this situation is that rhyolite is lighter than basalt, and wants to rise. As it rises, the basalt mingles with more and more of the non-eruptible rhyolite, gradually heating it. From this point, you get more buoyant rhyolite rising and mixing, and a chain reaction is formed. As the rhyolite rises further in the crust, the gas starts to come out of solution, increasing the pressure incredibly fast. If enough gas gets released (it can stall of course), the rhyolite will break open to the surface, starting a second chain reaction.

      The first rupture on the surface would subsequently eject quite a bit of rhyolite and basalt, although it wouldn’t be anything ludicrous. The problem is that once that first rupture occurs, any nearby rhyolite that was perhaps not reheated by the basalt injection will also become greatly depressurized with the vent opening. This triggers more rhyolite to degas and erupt, and the process carries on until it runs out of fuel essentially.

      Henrik’s rocket engine analogy is pretty spot on in my opinion.

      • TLDR:

        Supervolcanoes are able to form massive magma chambers that don’t erupt frequently because they form at a greater depth than normal volcanoes. The depth of these massive magma chambers is a result of melt from underplating, which occurs largely due to crustal extension.

      • These are good points! The depth of the original magma chambers has been derived from the pressure at which the crystalization occurred. That gave 10km. The magma was strongly ‘zoned’, into different layers with different composition, and had been separating for 150,000 years or more. That means any new influx of magma (which would have re-melted and re-mixed the chamber) was limited. You are right in pointing at the buoyancy of the magma and the importance of the crustal thickness. Under the right crust, supervolcanoes can erupt spontaneously just from their buoyancy.

        Toba’s magma was perhaps not as deep as Taupo. Still, the chamber was not much less than 10km deep. A shallow chamber just can’t sit quiet for that long.

        • Interesting – didn’t know this. That’s surprisingly shallow all things being considered (although 10km is still deep in the grand scheme of normal volcanoes).

  9. Sumatra has many more volcanoes some are close by, so it could happen again further south in time, like a zip unraveling when conditions are right ? the resurgent dome would be in line with the two large 8+ plus earthquakes in the Indian ocean, there seems to be a crack and the plate is splitting there, just thinking not an expert

  10. “Chickenshit” Yup, that’s me. Bonafide grade “A” chicken feces.

    I gave up on mowing the lawn. A thunderstorm is rolling through. Like volcanoes, your best chance of survival with Lightning, is to not be there when it does it’s thing.

    I now have a stripe down the middle of my yard about 8″ wide of uncut grass. I wear the stripe of shame with pride. It’s there, and I am alive.

    BTW, if you are milling about and there are storms in the area, and you notice the hair on the back of your arm is standing on end… you may have a serious problem in a couple of seconds. Eons ago, I was at a girls birthday party from my school. The get together was set up in the carport and her parents were chaperoning us. Some of us had this hair standing on end phenomena. A few moments later, a tree at the top of the hill exploded when lightning took it out.

    • As a storm nut I totally agree with you. There’s watching storms, and there’s being downright cautious! Walking into my workplace one stormy morning I felt all the hair go up on my head. I dashed for the back entrance like I was on steroids. No lightning landed, but I wasnt taking any chances! Lightning needs serious respect.

    • Difficult when you are on the top of etna. Only time I ever had it happen but the hair effect was the same as a van der graff at about 1,000,000V. I was quite concerned and the guides tried to (coolly) get everyone back into the coach (4wd ruggedised).

      Luckily the lightning didn’t happen, but it did later when we had gone.

    • It could perhaps be related to the magma chamber cooling down a bit over time.

      Chesner states “YTT [..] consists of an extensive, mostly non-welded outflow sheet with abundant pumice blocks (<80 cm) [..] Where deep exposures are available, the YTT is seen to be incipiently to densely welded towards its base."

    • I would personally wager it to be a product of multiple and separate magma chambers. You could easily fit 10-12 normal arc-based stratovolcanos inside the toba caldera, and I wouldn’t be surprised if you would have a bunch of smaller stratovolcanos with significantly more shallow magma chambers in the area prior to the big eruption. These magma chambers would be a product of normal arc-based magmatism, while the deeper chamber cooked the rhyolite to form the big one.

      This of course is just educated speculation.

  11. Are there other websites that chart earthquakes under volcanoes like the Icelandic meterology office? I’m looking for info on earthquakes as they happen in South America. Some leads would be great.

    • Quite possible. Eschenbach is quite focused on the self regulatory aspect of the atmosphere, specifically that thunderstorms form and act as a thermostat due to the heating of the tropics. As they form, they cut back on the energy influx to the oceans surface. I’ve seen the effect here in Florida quite a bit. With heat stress values up around 106°F or so, when you get a storm rolling through, it will shade the sun and the rain will drag the temps back down to the 85° to 91°F range.

      Also, his observation that the long term effect of the sulfate loading is overestimated is supported by what I found while looking into sulfate residence times. What I found showed that the sulfate was effectively scrubbed out after 50 months.

    • The choice of which temperature record to use is important. This one uses an average of land-based measurements, which is both more responsive and noisier than land+sea measurements. Some large volcanoes have a notable effect on temperature, especially in the northern hemisphere, lasting 1-3 years. Others do not. The effect of Tambora is actually very strong in the Berkeley record (the one used by Eschenbach): http://berkeleyearth.org/summary-of-findings/

      https://volcanocafe.wordpress.com/2015/05/20/volcanic-winters/

    • Since the other site was effectively stolen and that we have no way of keeping aby link there from being modified to point towards something other than what was written, it’s not a really a good idea.

      We have already seen comments and posts there deleted or changed. If you send the link to the VC email here, we can try to locate the data in the archive and possibly recover it.

        • The next NDVP is pending. There are a couple of other posts that are scheduled in the meantime.

          As for restoration of older stuff, that is a matter that can be subject to litigation. If it’s a Ruminerian post, VC.org can republish it at will seeing as that I wrote them. Whether to revamp them and present them as a new post is problematic, I don’t want to bore people and some of my stuff is a bit tedious.

          • get the beachballs one back when you have a moment – that was really good. as for the rest definitely dull and dreary …. (tounge firmly in cheek) but you should set up a super post – which a bit like a section of the library – all your posts linked within it with highlights in the superpost so that people can dig into the detail or just get the juicy stuff 🙂

          • I retained copyright to some of my stuff, so if you want to use it, I can give the necessary permission.

            If I wasn’t blocked from the old site, I could retract permission to use from there.

    • And the official word is that individual users can link what they wish (baring explicit stuff or SPAM.)

  12. Hi, I’ve been lurking for quite a while and I have really enjoyed learning about volcanoes.

    After looking at the map in this article, I have a question. Why are there no large volcanoes in the Himalayas?

    Thank you!

    • “During the Upper Cretaceous, about 70 million years ago, the north-moving Indo-Australian plate (which has subsequently broken into the Indian Plate and the Australian plate[6]) was moving at about 15 cm per year. About 50 million years ago this fast moving Indo-Australian plate had completely closed the Tethys Ocean, the existence of which has been determined by sedimentary rocks settled on the ocean floor, and the volcanoes that fringed its edges. Since both plates were composed of low density continental crust, they were thrust faulted and folded into mountain ranges rather than subducting into the mantle along an oceanic trench.[3] An often-cited fact used to illustrate this process is that the summit of Mount Everest is made of marine limestone from this ancient ocean.[7]….. ”

      When plates are in collision especially oceanic plates hitting continental crust, the oceanic plates tend to dive down under the continental crust and eventually dive so deep they start to melt and release gasses. This melt zone is of relatively lower density then surrounding areas and magma then can start to rise and break through the crust and form volcanoes. These volcanoes are often hundred(s) of km inland from continental boundary.

      See: https://en.wikipedia.org/wiki/Himalayas#Geology

      • or in simpler terms – nothing got pushed underground – so nothing melted, so no melted rock trying to float back to the surface.

        • Basically correct but it is a bit more complex. You get much thicker crust underneath the Himalayas: some rock is pushed up but other is pushed down. But only to ~50km deep, not the insane depths of subduction zones. Still, it is deep enough to get some melt, and in fact there are granites in the Himalayas. Granite is melted rock which has crept upward. but it wasn’t deep enough to be heated by the mantle, so the melt fraction stayed small. Not enough to drive a volcano, apparently.

      • Not coincidentally, one of the largest, if not the largest, volcano ever happened “next” to the Himalayas at that time and wiped out 90% or so of the species on the planet Earth, the Deccan Traps.

        See, I learned something by lecturing at my grand-daughters 6th grade science class.

        • In some level of fairness, calling the Deccan traps a single volcano wouldn’t be that much different than calling Iceland one volcano. They’re not all that different from each other after all. Iceland is essentially an active flood basalt event, it’s just not super easy to see that considering the fact that flood basalts occur over million + year periods.

          Also, the Deccan Traps event did not wipe out 90% of species on earth. The only extinction event to come close to 90% of life on earth was the P/T boundary event, which coincided with the Siberian trap volcanic period. This is also coincidental with the Chicxulub impact event, which supposedly killed the dinosaurs (although it may have been a variety of factors).

          From http://www.endangeredspeciesinternational.org/overview.html

          “Finally, the Cretaceous-Tertiary extinction occurred about 65 million years ago and is thought to have been aggravated, if not caused, by impacts of several-mile-wide asteroid that created the Chicxulub crater now hidden on the Yucatan Peninsula and beneath the Gulf of Mexico. Yet, some scientists believe that this mass extinction was caused by gradual climate change or flood-like volcanic eruptions of basalt lava from the Deccan Traps in west-central India. During this extinction, 16 percent of marine families, 47 percent of marine genera, and 18 percent of land vertebrate families including the dinosaurs. “

          • By that, I mean the deccan traps were coincidental with the chicxulub impact event, not the siberian traps.

            Nonetheless, for each extinction event, it’s highly likely that a large variety of conditions created the resulting extinction events. Trap events have been traced to multiple extinction events, but there have also been massive flood basalt ./ trap events that resulted in almost no extinction. We are also currently living during an ongoing flood basalt event that isn’t all that much less vigorous than other large flood basalt events (Iceland).

            One, and possibly the most plausible argument is that many of these events were part of a series of cascading failures that caused mass upheaval of ecosystems. The cause of said disruptions could be many things, some of which are independent, others could possibly be related.

          • And that meshes quite well with the coincidental multiple stressors overwhelming a species ability to deal with them. Singly, the individual events can be dealt with and survived. Encountered at the same time or pretty close in time, as a group, the species dies off.

          • Chixilub was probably the worst place for it to hit. The impact region had a lot of molecularly restrained gases that were instantly released. Gigatonnes of Carbon in the form of CO2 and CO were injected to the biosphere. I imagine the plants that survived were quite happy with it. The Trapps were steadily releasing SO2, and may have been put into overdrive by the roughly antipodal position of the impact when the shock waves coalesced near their position.

            Note: The Antipodal hotspot ideal is a bit contentious, but here is the paper.

            http://www.mantleplumes.org/WebDocuments/Antip_hot.pdf

            Effects of a 6 mile wide impactor at typical asteroid velocities would have generated roughly Mag 10.0 shaking. Pre impact energy was about 1.30 x 108 MegaTons TNT.

            http://impact.ese.ic.ac.uk/cgi-bin/crater.cgi?dist=1000&distanceUnits=2&diam=6&diameterUnits=4&pdens=&pdens_select=8000&vel=17&velocityUnits=1&theta=45&wdepth=&wdepthUnits=1&tdens=2500

            “The crater formed is a complex crater.
            The volume of the target melted or vaporized is 3430 km³ = 822 miles³
            Roughly half the melt remains in the crater, where its average thickness is 590 meters ( = 1930 feet ). “

    • There is the Kunlun Volcanic Group in Tibet, which appears to be near the collision zone. Its lavas are trachyandesite and andesite, typical of a subduction zone.

      However, when I plotted the earthquakes further over to the east, there may be a very shallow subduction zone. Heard somewhere that the crust there is too dry for hydration melting.

  13. Well, the end of the world is officially here. It’s been good knowing you guys.

    How do I know? Easy, Amazon, one of the original dot coms, posted a profit.

    • Well, in 50+ years of puttering around on the planet, I finally bought an electric razor.

      • Why in heavens name would you do that? I have used disposable razor for years. One razor easily lasts the 6 weeks of our annual slog. Of course, I have a beard so do not have to shave very much facial hair. lol. Don’t need shaving cream either for trips, although I do use it at home. On trips, just lather up a bit of hand soap and away you go. Keeps weight way down when traveling with only one back pack for two people plus a small day pack for side excursions.

      • Why? Because sometimes I have to get out of the door and on the road pretty quickly. Negotiating the curves and turns around my goatee can be time consuming, especially with a blade. Nix the goatee? Not gonna happen. 20 years of keeping a close cut military haircut only deprived me of years of having hair. Now I have the genetic predisposition to baldness coming on line and the facial hair is my crutch. The issue with that is that I don’t like motoring down the road and coming to the realization that half my face has hair where it shouldn’t.

        The goatee is nearly a beard unto itself, sans sideburns.

    • It is just an extreme case to test the influence of rain on flank collapses..

      • it depends how much, what about a Taifun / Cyclone those can bring massive amounts, the Philippines get a lot of those, mudflows are common there

  14. @TGMcCoy. Evidently the California Legislature has got your back. They pushed/are pushing legislation that will prohibit drone activity in off limits areas… such as near wild fires.

    I know that our Lifeflight pilots are hyper paranoid of ultralights. All to many times have they been enroute to an incident, in a helo, hauling ass at just above treetop level only to have an ultralight come popping up along their path. I imagine a drone is much scarier since they aren’t as easy to see.

    • Yep, in a recent incident near Palmer Alaska, they had to keep water-drop planes away because there were so many newspaper drones filming the fire. Same concern you post above. Bunch of houses lost because of that.

    • You know, if they hard-capped the altitude via software, it wouldn’t be as much as an issue. chip based barometric sensors are not that expensive any more. Failing that, they could just implement it via accelerometers that tally up the vertical distrance traveled and then limit based on that. Accelerometers with the requisite sensitivity are quite inexpensive nowadays. I even have one that I have been playing with that I ordered online. It is sensitive enough to where I could detect “first motions” in the shock wave from a 20 kg mass dropped a distance of one meter at 10 meters range. (this is related to what goes into a beach ball analysis. What I found was that on all quadrants, the mass striking the ground generated tensile forces as the ground was initially pulled towards the impact.)

      This came as the result of discussion/debate about lawn darts that Carl and I had.

      If I ramped this up a bit, it would make a fantastic high school science fair project. My issue with going any further with this is that discharging firearms in the area is illegal, and I would have to devise a firing mechanism to discharge a shotgun shell into the ground. Some Seismological studies use such a device to generate a known shock signal for reflection analysis. In order to sync my accelerometer I would have to do a bit of modifying to the trigger circuit, doable, but I don’t know if I really want to get that elaborate. A rudimentary seismic array could be put together for a bit under $500 or so. But, you would have to manually stack the traces in your computer from the data sets off of the sensors.

      If I ever decide to look for potential sink-holes, it might be just the way to do it.

    • Seems to have gone back down again. Others in the area seem to have had a few glitches so can’t see what was going on.

      • Looking at seismograph now, seems it’s malfunctioning, maybe that gives false data. Sorry I didn’t check that before.

  15. I’m back from Iceland 🙁
    My latest blog post is more “volcanic” than usual so I’m sharing the link here. If I’ve got anything wrong, please do let me know (kindly, and with respect for my general ignorance and spending less than a year learning about this, starting at as close to zero knowledge as one can have.)
    https://visitingnornahraun.wordpress.com/2015/07/25/as-close-as-i-could-get-helicopter-continued/
    My next few posts should also be “volcanic” as the entire helicopter trip was focused on visiting volcanoes.

    • For those that don’t know, the problem with daylight will be from the background “noise”. The ambient light would make it more difficult to pick out a return signal from the ash particles.

  16. Here is a really excellent article in a popular magazine on earthquakes and plate tectonics. I commented on the potential for catastrophic earthquakes in the NW including Vancouver Island where I lived for a number of years.

    http://www.newyorker.com/magazine/2015/07/20/the-really-big-one

    This kind of article should be interesting to people like Quail (23/07/2015 at 04:41) who are trying to understand basic geologic science and volcanoes.

    • And a critique of the image they used to illustrate the article. It is erroneous. It depicts a rupture encompasing the Cascadia subduction zone as well as most of California down to Baja. The Cascadia subduction zone STOPS at the Mendocino triple junction. From there south is the San Andreas, which turns at about LA and heads out the desert down the edge of the Salton sink. South of the Salton Sea, it becomes the Imperial fault. Both the San Andreas and Imperial faults are strike-slip. (left-lateral) The Cascadia is a thrust fault. (specifically, a megathrust fault where there is energy stored in the flexure of the overiding plate that can add energy to the quake when it springs forward like a bow releasing energy when an arrow is shot. Other than that, it seems like a good article. One major diffence between teh Cascadia subduction zone and the one off of the Japanese coast, is that the Cascadia does not have as large a subducted section tugging on it as the Japanese one does. It is generally believed that the Farallon plate separated from the Pacific plate (likely along the spreading center boundary) after it was fully subducted, and that the eddy currents in the athenosphere as it detached could have been partially to blame in triggering the Columbia river flood basalts, because their formation is roughly coincidental in geologic time to this happening.

      • you are right, the image seemed so trivial I did not pay attention to it. (: – o) . The article points out the lack of preparedness, It is not uncommon in many parts of the world. After all one must keep the economy going, no matter the consequences, right!

        • I lived on the Oregon Coast for 22 years.
          Down on the South Coast then the start of the Central coast-Coos Bay.
          I truly will not live there and have hard time visiting because of that ‘ol Demon that lives in the cold water-the Cascadia.

          I was a Real Estate agent in Coos Bay
          (Side note: got back into Aviation because it’s cheaper and I can sleep at night.) The local Board of Realtors thought it would be a good idea to print out a brochure on Tsunami escape routes and what to do in an earthquake. . From the the powers the be we would’ve been better off publishing a guide to the local Pornshops and Brothels.. It was incredible. I was told by city officials to
          “Back OFF!!” “Our turf!!” So I and the others did…
          Now I am home in NE Oregon and all I have to worry about is the OWL
          https://en.wikipedia.org/wiki/Olympic-Wallowa_Lineament

          • The only problem with the OWL is that no one is exactly sure what it is…

            It’s got old features and young features, and they don’t always match up to a cohesive picture as to what caused it.


            Edit Add:

            Here’s a thought for you. WHAT IF, the OWL is a megashear structure that ties into the northern end of Walker Lane? It would make sense from a fragmenting crust point of view. The biggest issue is that Walker lane seems to be a young (and forming) transform fault system. A series of Riedel shear structures much like the cracks (sprungur) manifested along the SISZ in Iceland along the southern extent of the Hreppar microplate. (oddly enough, with Hekla being a volcano built on top of a fissure at the end of those cracks)

          • Yes I agree. I think the may be something like your scenario going on..
            As soon as I get done with my Fight Instructor’s renewal I will get to my long unfinished post..-

  17. Hey!
    What is going on at Cotopaxi right now? It has become quite silent around this topic.
    Btw, awesome community – I’ve been following the site for quite some time now. I really enjoy the DVP – when is #5 going to be online? Keep up the good work!

    • Right now, it’s just a situation of sit and wait as boring as that may sound. The earthquake patterns have changed every few days, but they haven’t become more intense specifically, at least not where you would ring the alarm bells that an eruption is nearing. Many volcanoes like this will shake for months prior to an eruption, often waxing and waning in earthquake power.

      Part of the issue with this is that we don’t know how much activity will be needed to set off an eruption. Some volcanoes don’t show tons of seismic activity prior to an eruption, many of these being more “open” systems. On the other hand, there are volcanoes like Chiles / Cerro Negro which has been experiencing a swarm for almost 2 years at this point without eruption. Chiles is a volcano that is likely currently in a state of reactivation, so the lack of access to the surface has likely made it pretty difficult for any magma to make it to the surface.

      Cotopaxi is likely much more “open” than Chiles / Cerro Negro by comparison, but we may need more energy for any magma to break through. The current swarm we’ve seen IS way more energetic than anything that has been historically seen here, but that doesn’t necessarily say much. Also, compared to other stratovolcano pre-eruptive sequences, it’s been comparatively weak, but this also may just be the start of the sequence.

    • Because of an increased interest on the part of the Japanese scientists…. just hazarding a guess.

      Previously, on one of the helo surveys they noted damage to some of the walkway structures but had no clear idea of what had done it.

      If the steam get dark, or dark gray… it might not be steam.

    • Our authors are currently on vacation, but not too worry, they will be back shortly and until then we’ll have a new post up shortly 🙂

    • “I thought the plan was…” plans are like that. If you think this is bad, try planning out the refurbishment of all departmental spaces for a yard period (complete with resource assignments and personnel schedules) only to see the whole thing shot to hell and back because the Department head does a swap of compartment ownership with another department a week before you go into dry dock… then comes up with budgetary assets to send personnel through training. Schooling involves a whole new realm of requisitions, travel, berthing arrangements and clearance messages.

  18. What is going on south of Fox islands in the Aleutian islands. Is this a normal pattern for that area?

    Mac

    • Well, the pacific plate is sliding under the Aleutians at between 58 to 73 mm/yr, so it’s bound to make a bit of noise once in a while. Whether this quake sequence signifies magma movement towards one of the Aleutian volcanoes has yet to be determined. The Mag 6.9 shows thrust fault characteristics (from the USGS beach ball) so I would think that things are about normal. At 29km depth and being south of the islands points to it being along the benioff zone.

  19. I thought the discussion here on this post was excellent. Thought provoking and exploring comments and questions, and lots of knowledge exchanged. I certainly learned a lot. Thanks to everyone for their contributions!

Comments are closed.