The living Earth: Rocks, plumes and hot spots. Part II

Living plumes

In the previous post we went through some of the background to this post: the structure of the Earth, the change in minerals at various depth in the mantle which change the density, and a bit on seismology which can show how the temperature changes with depth. Now it is time to see what we can do with this knowledge, study the alien life of the Earth – and find the Earth’s heart.

Seismography has shown us how the conditions in the mantle change with depth. But there are deviations: not all places on Earth have the same mantle structure underneath them. There are locations below which the earthquake waves travel unexpectedly fast or slow. Some of these we understand. For instance, S-waves in subduction regions show high velocities, indicating low temperatures. The subducting slabs are cold and hard, and therefore resistant to deformation. The shear wave velocity is particularly sensitive to this: in harder material, it travels faster. Think of the students in the previous post: if they push back hard against the wave coming from behind, they push the person in the line equally hard. A hard push gives a fast response, and therefore a cold slab has a higher vs than a warmer, softer slab. Try kicking a deflated football and compare it to one at full pressure, if you need experimental evidence (always recommended). In these places of subduction, the high shear wave velocity reveals the departed but still cold ocean floor.

Other anomalies are not nearly as well understood. In particular, there are two very large regions in the lower mantle where the shear wave velocity decreases significantly. ‘Significant’ means by around 1-2%. This does not sound dramatic, but it is far more than expected. The two regions occupy around 8% of the volume of the mantle.

These two areas of tardiness have become known as ‘Large Low Shear Velocity Provinces’. The name kind of makes sense: the waves are shear waves, they are slow, and the regions of slowness are very large and therefore are called ‘provinces’ rather than say ‘spots’. (But ‘Large’ and ‘Provinces’ does seem a tautology, saying the same thing twice.) However, it is clearly a name designed by committee. Nowadays it is abbreviated as ‘LLSVP’ which to me still sounds like a quango! Wikipedia calls them ‘superplumes’, whilst the term ‘superswells’ is also in use; both names, however, are also used for other (perhaps related) phenomena. The name ‘thermo-chemical pile’ has been used in scientific papers but this sounds like a severe and socially inhibiting disease. The plethora of unhelpful names shows that the understanding of them is still lacking. Once we know what they are, a more palatable name (not involving piles) will be invented.

Source: Cottaar & Lekic, 2016, Morphology of seismically slow lower-mantle structures, Geophysical Journal International, Volume 207, Pages 1122–1136

One of the regions is located underneath Africa, and the other is almost (but not quite) opposite, underneath the Pacific. They sit on top of the core-mantle boundary, entombed within the lower mantle. The two regions have different shapes: the Pacific LLSVP is roundish and the African LLSVP has a more complex shape, elongated north–south with two extension east-west. The African LLSVP also reaches much higher than the Pacific one. The Pacific LLSVP extends 700 km above the core-mantle boundary, with the top about 2300 km below the surface. The African LLSVP is more than twice as high, with its top at 1600 km: it reaches halfway to the crust. They are still quite flat structures: the width of perhaps 5000 km or more is several times larger than the height.

Exploration

The explanation of the LLSVPs has been discussed for decades. They may be (likely are) zones of higher temperature (because of the lower shear wave velocity), but they may (likely do) consist of rock with different composition. Perhaps they are both. The first suggestion are the so-called ‘thermal models’, and the second are the ‘chemical models’. Combining both models, the LLSVPs are known as the thermo-chemical piles (this is where that name comes from), where the words cover pretty much all possibilities while staying safely on the geological fence – even the term ‘plume’ is carefully avoided.

But are the LLSVPs mantle plumes? It is tempting to see them as the rising part of the mantle flow, countering the descending subducting plates. But if they are ascending, why don’t they reach higher? And models show that a hot rising plume in the mantle becomes narrow and tall, while these structures are very broad. Perhaps they consist of a large number of narrow plumes, which in the data appear as a large structure. But that would still not explain why they stop halfway. No, they do not appear to be mantle plumes.

The most likely model for the LLSVP is that they consist of slightly heavier minerals than the rest of the mantle. If the temperature is the same as that of the mantle, they will happy lie at the bottom. However, the difference in density is not large, perhaps only a few per cent, as is evident both from the fact that they don’t cover all of the bottom, and that some parts have managed to rise. A higher temperature can compensate for the higher density. The model assumes that the temperature varies throughout the LLSVP. All parts are warm, but not equally warm. Where the excess warmth is less, the LLSVP is denser and lies at the bottom. Where the temperature is a bit higher, the material expands a tiny bit, the density lowers, and the LLSVP begins to rise. But it does not rise very far, at most halfway up the mantle. This fact already indicates that they are different from the surrounding mantle, and they do not have exactly the same chemistry. The combination of lower and rising parts creates a dome-like structure, a bit like the plant at the top of this post (a yareta from the Atacama desert). Depending where you are, it could also be compared to the domes of the Sydney opera house or those of the Cornwall Eden project.

The two LLSVPs may have existed here for hundreds of millions of years. Deep in the upper mantle, they should leave no direct trace on the surface, 1500 km or more above. But perhaps surprisingly, there is one indication for their existence on the surface. It is visible in the terrain of Southern Africa. Don’t look for small things: as appropriate for such a large structure, go big. Step back and look from Afar. You can now see that the southern third of Africa is a high plateau, up to 2 km high and extending to almost the southern edge of the continent. (The low-lying strip between the high plateau and the ocean is some of the most beautiful land on Earth, in my opinion.) This six-nation plateau is much higher than a typical continental plate (500 meters). There is no clear explanation for this excess height: there is no mountain region (the Drakensberg are the edge of the plateau and are mountainous only from one side), no plate collision (not since before Gondwana formed), and no hot spot activity since the break-up of Gondwana. It has no known cause. There is only the LLSVP sitting below it.

Southern Africa is the only area where an LLSVP lies below a continent: all other regions above the two LLSVP are oceanic.

There is a second indication of a long-distance impact of LLSVPs on the surface, but we will come back to that.

Origins

The LLSVPs are old – old as the mountains (which actually are much younger – a case of our language lagging far behind our science). But where did this 8% of the mantle come from? How did it acquire a different composition compared to the rest of the mantle?

There have been many, always speculative, suggestions. One proposes an ancient origin, when the Earth was young and the mantle was a magma ocean. It solidified very quickly, but the magma ocean lasted long enough that the heavy iron was able to sink to the bottom and form the Earth’s core (that part is not speculative – it is the only way our core could have formed). It ended when the mantle solidified. Perhaps the bottom of the mantle stayed molten longer than the rest of the mantle, and the material from the LLSVP sank to the bottom of the mantle at the this time: it is a memory of when the world was young and life was still an unforeseen development. Other suggestions go off on more recent tangents. One proposal is that the LLSVPs are the remnant of the oldest crust of the young Earth, sinking to the bottom in the earliest subduction, a few hundred million years after the Earth’s birth. An even more speculative idea is that the LLSVP formed from the high density parts of subducted oceanic plates. An oceanic plate consists of the crust and the attached lithosphere. The idea is that when the subducted pate reaches the bottom, the crust detaches from the lithosphere. The crusty bit begins to rise as it warms up (think lava lamp) but the lithospheric bit stays behind. Both eventually dissolve into the surrounding mantle, but the region where the lithosphere was remains overdense. It is a rather complex, multistep model, and as with any complex model, it can explain a lot but is very hard to prove. It may have a problem with the clear separation between the LLSVPs and the rest of the mantle, and with the fact there are only two.

Combining the various proposals, the LLSVPs are sometimes described as a ‘melange’, a mix of all proposed components. The bottom of the mantle acts as the waste bin of the Earth: everything that isn’t wanted elsewhere ends up here. That makes the LLSVPs the Earth’s rubbish dump – although that is a term you will not find in any scientific papers.

There are some things we do know. If the sunken material were too dense, it would form a stable bottom layer like the D″ (remember, D-double-prime). That is not what we see. This also rules out more exotic ideas such as extraterrestrial impacts or core dredge-up. If it were the same density as the surroundings, it would relatively quickly get stirred into the rest of the mantle. That too did not happen. Creating a structure akin to what we see, rising domes in places, lying low in others, only works if the density is only a little higher than the surroundings, by a few per cent. It is like a lava lamp that it isn’t quite working: the blobs are shuffling around in the bottom half but fail to rise to the top. Blobs that are warm enough rise a bit, but become stuck halfway up and remain there, until they have cooled a bit and sink again. Such a failed lava lamp is dynamic but disappointing (so much so that not even youtube has an example, while working lava lamps have many hours of footage), and moves sluggishly. (Our garden snails would take offence at that term.) The LLSVPs may behave like this. A part of the denser material heats up (for some reason), rises, cools, and eventually drops down, while another part in the mean time has been heated and begins to rise in turn. Speed up the movie to show a billion years in a minute, and the mantle comes alive, with the LLSVP moving around in the lower mantle like a massive, monster amoeba. Or like a pumping heart.

Mantle cartoon; blue are the LLSVPs

The depiction of the mantle above shows the different parts. Yellow indicates the subducting plates, descending into the deep where they partly dissolve. Black is the normal composition of the mantle. Blue is the LLSVP that fluctuates along the bottom but doesn’t easily mix – sometimes a subducting plate will penetrate into it. The cartoon does not separate the lower and upper mantle, so it doesn’t capture everything. But it gives the idea of the life of the mantle.

ULVZ

There is one more component which we haven’t mentioned yet. At the very bottom of the mantle there are a few smaller regions where the velocity of the shear waves drops by a massive 20-30%. This drop is ten times more than that of the LLSVPs! The primary or P-waves (remember them?) also slow down here, but ‘only’ by 10%. These regions are therefore called the ultralow velocity zones (ULVZs). Scientific names may be accurate, but they do lack in impact, memorability or poetic power! Geology in particular has invented an obscure nomenclature, also known as geo-babble:

A geo-babble prosody

The language of geology
a whimsical neology
The lexicon is chockablock
with complex names for sandy rock

Starting as a periodite
forshape into a ringwoodite
reincarnate as bridgmanite
transfigurate to perovskite
continuing ad infinite

A wordy sample
of the lower mantle

The layers too have epithets
A glossology of figureheads
We persevere
with the asthenosphere
but nothing will rhyme
with D″
And the same is true, to a lesser degree
with the esoteric LLSVP

What you see is what you get
unless you name it ULV-zet
and if you read it ULV-cee
what it is you still don’t see

Vernacular etymology
obstreperous mineralogy
obfuscating, exasperating
the discombobulated uninitiated
through geo-idiosyncrasy

(Presumably professional geo-babble requires ownership of a Babble fish.)

(The story that the asthenosphere was made up by geologists, and that this is why it is called ‘as-the-no-sphere’, appears not to be true.)

Back to our story. All ULVZs lie at the very bottom of the mantle. They are typically a few hundred kilometers across, between 10 and 40 km thick, and are located directly on top of the D″ layer. They are tiny compared to the LLSVPs. ULVZs are very hard to detect, and only parts of the Earth have been investigated for them. On the map below, areas where they are known to exist are shown in bright red, and areas where they do not exist are blue. Note that the red areas are not the shape of the ULVZs: they indicate that one or more ULVZs exist somewhere within the red area but their shape or size are not known. The LLSVPs are indicated as the pinkish regions.

The known ULVZs are mainly seen around the edges of the LLSVPs (writing a sentence with two long acronyms feels really scientific). The non-detections are mainly further from the LLSVPs.

We don’t know what the ULVZs are! Their relation to LLSVPs (if any) is hotly debated; the shear velocities are very different, suggesting they are not directly related but have different compositions. The location at the bottom of the mantle indicates a high density, and the low shear velocities suggests they could be partly melted. There are two main suggestions regarding their origin: blobs with enhanced iron-oxide, perhaps diffused from the core, or subducted ocean crust which has melted, with the densest material dropped to the bottom. The clustering around the LLSVPs can be a result of mantle circulation. If the LLSVPs have higher temperatures, then they can heat the mantle material around them. This begins to rise, and sucks in new material at the bottom. This causes a sideways flow at the bottom of the mantle, directed towards the LLSVP. The lateral flow takes the ULVZs along with it as a (perhaps unwanted) passenger, but once adjacent to the LLSVP where the mantle flow goes up, the ULVZs are unable to rise with because of their higher density and they are ejected from the flow. This leaves them stranded on the beach of the LLSVPs. Think clogged arteries.

There is one rather intriguing aspect to the ULVZs. Some (not all) seem to be related to surface volcanism. Both Hawai’i and Iceland sit above a nearby ULVZ. In the case of Hawai’i, the ULVZ is located just to the west, and for Iceland it is a little to the east. This is surprising, in view of the separation by three thousand of vertical kilometers and the fact that the ULVz are immobile and stuck at the bottom. However, a relation to the surface volcanism is far from proven. People may just have looked for ULVZs mainly in such areas of interest. The data is suggestive, but not conclusive.

Hot spots

We have seen that one of the LLSVP seems to be pushing up Southern Africa over an area 1500 km in size, whilst ULVZs may be related to volcanic island hot spots 3000 km above. Could LLSVPs also be related to hot spots or is this a monopoly of the ULVZs?

Hot spots are locations where volcanoes are active but which lack a clear reason for why there should be a volcano there. Volcanoes are expected at mid-oceanic ridges and above subduction zones, both at the edges of plates. In contrast, hot spot volcanoes such as Hawai’i and Yellowstone can be located in the middle of a plate. Their activity requires an underground heat source – hence the name ‘hot spot’. The source of that heat may differ between hot spots. In some cases there is a clear connection deeper into the mantle, in other cases there isn’t. Where there is a signature of a connection, it often ends midway in the lower mantle, as for instance in the Galapagos. Plumes from the core-mantle boundary are a rarity – perhaps even non-existent. But starting a plume in the middle of the mantle just moves the problem, for why would there be a heat source there?

From McNamara 2019: A review of large low shear velocity provinces and ultra low velocity zones, Tectonophysics 76, 199

The map above shows the locations of the known hot spots. The size of the orange circles showing the magma production rate, in the slightly funny unit of mega-grams (or tons) per second. The known hot spots tend to be located around the LLSVP regions, and are often near their edges. Can it be that some hot spots are somehow powered not by the ULVZs but by these LLSVPs? This would explain why hot spot plumes can often not be traced to the bottom of the mantle.

It gets even more interesting when looking at past flood basalts. (These are also known as large igneous provinces, or “LIP” in this acronym-flooded field (AFF)). The LIP is a sure sign that there was a hot spot there in the past. These (now extinct) hot spots have been added to the map above, and are shown as the green circles. The positions are corrected for plate motion. For instance, the Columbia flood basalt is plotted not at its current location but near Yellowstone, which is where the flood basalt actually occurred, before the moving continent carried the lava shield away. Almost all the LIPs are located above the LLSVPs! And just as for the current hot spots, they have a tendency to go for the edges of the LLSVPs, not their centre.

A mantle wind

The relation between hot spot volcanism and LLSVPs is intriguing. Both the hot spots and the ULVZs are found around the edges of the LLSVPs, but the ULVZs are at the bottom and the hot spots are much higher up.

The LLSVPs themselves are largely immobile, while the mantle flows around them at a leisurely speed of perhaps half a meter per year. The LLSVPs are warmer than the surrounding mantle and pass on some of their heat. Around the LLSVP you get a thin, warm mantle region. This begins to rise: there is now a mantle updraft around the LLSVP. The LLSVP stays where it is (it is too dense to rise any further) but it powers the updraft around it.

This basic model is shown above. The subducted plate comes down to the core-mantle boundary and moves along the bottom. Where it reaches the region of the LLSVP a sharp boundary forms, the mantle winds moves upward, and from the heated edge of the LLVSP a thin plume begins to rise. This plume will form the hot spot where it reaches the surface. In the depiction, the plumes come from the LLSVP itself. In reality, it appears to come from the surrounding mantle.

So hot spots and related volcanism appear to be closely related to the LLSVPs.

To rise and fall

There are two circulations in the mantle. In the upper mantle, the circulation begins with inhalation of old oceanic crust in a subduction zone, and ends with exhalation at a mid-oceanic spreading zone. Most of the time this circulation remains within the upper mantle, although sometimes the subducting crust is cold enough to sink into the lower mantle while some hot spots break through the other way and disturb the breathing cycle of the upper mantle. This cycle of the upper mantle is powered by the subduction of the oceanic plate which pulls the rest of the plate sideways. This causes the plate to tear, creating the weakness of the mid-oceanic rift where the mantle material can find its way back to the surface, closing the cycle.

The lower mantle also has a circulation. Part of this is a slow convection that remains confined to the lower mantle. But there is some interaction with the upper mantle, especially when a cold subducting plate reaches the lower mantle and plummets to the bottom. Convection is driven by heat from the below and it doesn’t like a cold bottom. Instead the plummeting plate causes a downdraft behind it. This disturbs the circulation of the lower mantle and pushes the updraft away from the frigid plate. Over time, perhaps a few hundred million years, the plate on the bottom warms up. Now it becomes buoyant again and begins to rise. At this time it will also begin to dissolve into the lower mantle.

The role of the LLSVP in this process is absent from the youtube simulation (it just has a heat source below the centre), but appears to be quite important. The LLSVP causes local regions of updraft. The mantle material just around the LLSVP is heated and rises, and this pulls in new material from the sides. The excess heat triggers a narrow plume which may be hot enough to break through the barrier, enter the upper mantle and cause a hot spot. A volcano will now erupt. The sparsity of hot spots already shows that this does not happen everywhere around the LLSVP. Only a few regions become hot enough to do this. One suggestion is that regions where an old oceanic plate mixed into the mantle are especially susceptible to form such plumes, because they have slightly lower density (due to the mixed-in oceanic crust). The extra heat makes them more buoyant and they take off, leaving the rest of the mantle behind.

This predicts that mid-oceanic ridges have different magma from hot spot volcanoes. Both produce basalt, but mid-oceanic ridges are largely recycled oceanic crust, while hot spots are mostly unprocessed material from the lower mantle. (Whether they could contain any material from the LLSVP itself is disputed.) Indeed, the basalt from hot spot volcanoes is more primitive, differs somewhat in the ratio of chemical elements and contains more of the rare isotope 3He which is strongly depleted in the upper mantle (and is therefore very very expensive!). There is also more diversity in the magma from different hot spot volcanoes.

Whilst the upper mantle circulation is powered by descending plates, the circulation of the lower mantle is powered by the heat from the LLSVP. The upper mantle inhales – the lower mantle pumps.

This still begs the question why the hot spots are mainly found around the edges of the LLSVP. For if they get their heat from the LLSVP, why wouldn’t the central top of the LLSVP heat the mantle directly above it just as well? At first thought, the answer to this seems simple. Assume that every square meter of LLSVP surface heats the mantle with the same efficiency. Where are those surfaces? Imagine a cube sitting on the mantle floor. It has 6 sides, 5 of which face the mantle (the 6th is the bottom and faces the D″). One of those sides is the top, and four are around the edges. So the surface area around the edges is four times larger than the surface area on top. A quick count of hot spots on the map above shows that around 20 are on edge and perhaps 7 are more central. That is a ratio of 3 to 1, not far from 4 to 1 expected for a cube. This is the simple answer, but it falls flat because the LLSVP is not a cube and is much wider than it is high. The excess surface around the edges is now much less. Using the dimensions of the African LLSVP, it now predicts that perhaps half of the hot spots are at the edge and half on top. That is not quite what is seen.

A more difficult answer could be that a mantle flow rising around the edges can pick up more heat that one rising from the top. This is because an edge flow remains close to the LLSVP during the rise, while one rising from the top loses contact with the heat reservoir almost immediately. A combination of the simple and more difficult answer may work.

The second begging question is where does the LLSVP gets it heat from? There are two obvious possibilities. It may just be better insulation. The mantle transports heat from the core to the surface through convection. The LLSVP does not take part in that, and it only loses heat by conduction into the rest of the mantle, and this is a much slower process. Compare the temperature in your greenhouse with that of the air outside. The outside air convects, the air inside only conducts. (Interesting, a greenhouse is not heated by the greenhouse effect!) Less heat loss (hold it – this part is difficult, at least to some who prefer not to grapple with global warming) means that you stay warmer.

The heart of the matter

We started with a search for the Earth’s heart. We found that there are two cycles, one in the upper mantle and one in the lower mantle. The upper mantle cycle is compared to breathing (of healthy rock rather than air). In contrast, the lower mantle cycle is pumped by heat from the LLSVPs. The pump acts the same as does a human heart.

Thus, the mysterious LLSVP is in fact our planet’s warm heart.

There are many open questions here. At what depth does the plume form?. Does it come from the top of the LLSVP or does it start lower down? The data remains inconclusive. What is the precise structure of the LLSVP? The images look nice but we may be missing a lot of detail. Do they perhaps consist of clusters of narrow plumes, or are they indeed more like domes?

And what is an LLSVP anyway? What is it made of and does it really date from the earliest days of the Earth? And what are the even more mysterious ULVZs?

There is a final question. The mantle is a windy place, where nothing is stationary. That means the LLSVPs should also move around. In that case, why do even LIPs from 300 million years ago line up with the modern edges of the LLSVPs? Perhaps it is because LLSVPs move only very slowly. Models suggest that their viscosity is ten time higher than that of the average mantle. The movement may be sluggish enough (with apologies to our rocket-like garden snails) that they don’t move far in a brief 300 million years.

But if they move, why should hot spots be stationary? And even if the LLSVP is stuck, the hot spot should still be able to move around the edges of the LLVSPs. There are in fact indications that hot spots do move around, and have not always been at the place where we see them now. The Hawai’i hot spot may have moved by 10 degrees in latitude over its life time.

Attempts have been made to model the mantle wind, taking into the effect of the changes in the location of subduction zones over time. Around 700 million years ago, there was a network of subduction zones around western Gondwana. 200 million later those cold subducting blocks reached the bottom of the mantle. Another subduction zone formed 400 million years ago around the northern edge of the Tethys ocean, and the process repeated here. The clusters of hot spots and LIPs occur above these locations: perhaps the plumes surrounding the African LLSVP are a memory of Gondwana, rather than the direct trace of the large low shear velocity province. The LLSVPs activated them but the fuel came from the Gondwana. Perhaps.

Hidden life

The life of the Earth is like the cicadas who live in the dark, unobserved, for 17 years, before making their brief but very loud appearance above ground. We only see 1% of their life, and have to guess about the other 99%. For the Earth, volcanoes are that 1% we can see. The other 99% of the life of the Earth is underground, much like the living rocks which Spock referred to. We hear the noise, but fail to see the party underneath to which our homely continents are not invited.

We started this series with Spock’s famous statement from Star Trek: ‘It is life, Jim, but not as we know it’. (The one he never said.) But now we have the answer, and it turns out the Earth’s life is very much as we know it. The clue is in the tautological LLSVP. For the Earth has two of these, and thereby has two hearts. The Earth is like the only alien more famous than Spock, the one with two hearts. The Earth, it turns out, is Doctor Who. We have been studying a Time Lord. We are Gallifrey.

Perhaps this is the reason for the unearthly language of geology.

Albert, June 2022

Doctor Earth, residing in the lower mantle

133 thoughts on “The living Earth: Rocks, plumes and hot spots. Part II

  1. Now all we need, is an article about the Earth’s Core. The Mantle is fascinating, but not all of what is within Earth.
    Problem is… how much do we really know about the Core?

  2. As someone who is intimately familiar with the literature around this topic, as I read your text (and the previous installment), in many cases, I can identify the precise paper which you are paraphrasing or riffing on in a particular section. This has me wondering why you neglect to cite those sources, or at the very least, prepare a bibliography at the end of your posts, and give some credit (and some further reading material for your visitors) to the scientists who have labored over these discoveries and theories for decades. It’s a bit unseemly, in my opinion.

    PS: the cartoon credited to McNamara’s 2018 review in Tectonophysics is actually a diagram Courtillot et al. published in 2003 in EPSL. McNamara only reuses the diagram, and he does so in the context of 5 other schematics by other workers, laid out in a grid, to visually showcase the multitude of explanations that have been proposed on the topic.

    • It has been a longtime “standard” to not reference every single paper we use when we write.
      Normally we do it if a paper changes the perspective on volcanology or a certain volcano.
      And sometimes we dedicate an entire article to a single paper and that would certainly be referenced.
      This is common practice in popular science writing.

      It is also about readability. Obviously such a well published person as Albert knows how to do proper referencing, but it makes reading a bit “choppy”, and harder for the layperson.

    • That is a good point. These are meant to popular articles, not scientific literature. We try to reflect the best knowledge but obviously it is based on a limited set of papers. The main one for these two articles is, as you note, the Mcnamara review which is mentioned and is what people wanting more information should read. Further references are in there. We do read more and newer papers, especially when a point seems possibly more controversial. If an importance reference was missed in this post, I apologize. Some information came from Yuan & Li 2022 which should have been mentioned. The Cottaar & Lekic paper was mentioned.

      Sometimes a reading list is used but this quickly runs into two problems: the papers may be too technical, or the papers are behind a paywall. The latter is very common in this field and there is little point referring the readers to a paper they are not allowed to read themselves. Open access papers are becoming more common, but we also have more papers published in places that even many universities don’t have access to.

      • Agreed. This is not a learned journal and very much work goes into producing an article like this anyway. Any member of the public in any case rapidly finds a paywall block.
        Well done Albert.

  3. This little swarm of Thorbjörn comes with clear moving magma.

    Now for a nice friday read.

    • Seems inevitable, there will be an eruption in that area soon. Lots of times it is stated that only 1 in 10 intrusions erupt, or something like that. But the way I see it is that it actually is more like it can take 10 intrusions to trigger an eruption. At a less active volcano perhaps a failed eruption is a real thing, but in very active places with large magma flux an intrusion that doesnt erupt should be seen as a precursor to a near future eruption at that location.

      It is quite obvious when you look at locations of eruptions in the past 70 years at Kilauea. Both Mauna Ulu and Pu’u O’o had many years of intrusions and tiny eruptions at their respective locations before the main eruption began. I would be very surprised if there wasnt at least something similar in Iceland, the two areas are much the same in many ways and the magma is nearly identical.

    • Earthquakes have also gone quieter like before Fagrafjalls.

      A bold prediction? Eruption near Grindavik before end July? Something to be shot down in flames.

      • Eruption somewhere on Reykjanes seems likely before the end of the year. The last cycle did seem to have clusters of eruptions where many would happen over the course of a few years with a longer interval between. Sometimes this was a rift episode within one volcano but sometimes also between adjacent volcanoes.

        It is said that last years eruption was larger than average in volume just very limited in its extent by the topography. But I think that is not exactly very realistic, maybe large for its area but eruptions at Krysuvik and especially Brennisteinsfjoll are generally larger, possibly going to 2 km3 for the longest eruptions in the late 900s at the latter. Hengill is larger again, up to 1 km3 for its last 2 eruptions but these are curtains of fire, the whole thing mostly over in a week or two, a Laki type event just not in volume.

        Would not be surprised now a cycle has started if Reykjanes outperforms Vatnajokull and Hekla combined for number of eruptions this century.

  4. I wonder if the LLSVPs are as you say at the very end the heat scars of Gondwana. It has been said many times by various contributors that thete was a tremendous heat build up under the super continents, would this heat not cause the mantle to rise in the centre ie Africa causing tension within the continental structure, which eventually breaks, the separate pieces sliding radially outwards, ie Australia S America, India and Antarctica, with Africa sort of half in the middle moving slowly North. The same process may account for the break up of East Africa but on a smaller scale.

  5. With account to the flood basalts map, are all the (NUMEROUS!) previous LIPs surrounding the Siberian craton actually near to an LLSVP when accounting for plate motion, or are they not shown on there?
    The largeigneousprovinces website notes something like 30 LIPs around Siberia, Russia and Scandia.

    • I don’t think they are on the plot: it only includes LIPs with a deep mantle origin, and the Siberian traps are shallower. But I don’t know which ones are included,

    • Siberian Traps was a massive event .. must have formed by a core plume ..

      Was it shallow ?

      • That is under discussion. The melt happened under low pressure, relatively shallow. That suggests extension in the crust played a role. There is no evidence of uplift prior to the eruption. That would argue against a plume. However, it is possible that the uplift happened away from the known traps. It remains an open question. Note that ‘deep’ does not necessarily mean ‘from the core-mantle boundary’. Many seem to come from intermediate depth. It is all in the post ..

        • There is a hypothesis going around that the Siberian Traps were formed by some “hydro-plume”.

          It is basically a plume of mushy, buoyant rock that had their temperatures lowered by a presence of a little more water than usual brought by a “deep flat-slab” that happens when a slab stagnates at the Mantle Transition Zone.

          It may sound crazy, but Mount Peaktu is formed by the same process as described above. I have heard about it in that one documentary about Peaktu. It is a bit of a massive assumption, based on what I heard from these guys.

          • Is the implication that Paektu may ultimately be the location of a flood basalt event in the geologic future? Or is it a difference of scale (IE Siberian Traps representing a “hydro plume” event of far greater magnitude).

          • I think it more like that the Siberian Traps are on a much larger scale, but I should note that there are a few large basaltic volcanic fields near Paektu. It could be possible that it could be the next flood basalt event, but it would be highly unlikely.

            The largest flood basalt on Earth (as far as we know) is the Ontong-Java flood basalts at around 120 million years ago in the Pacific, when it unleashed around 80 million cubic kilometers worth of magma, covering about 1-5% of the total surface of the Earth.

            There is another type of volcanic province is the silicic volcanic provinces, which are basically similar to scale to flood basalts but having basalt as a minor component. I think New Zealand would become one (or is one) or the Andes possibly (if it is already, I kinda forgot) and many more. Those guys are more related to subuction zones rather than the usual hotspot or rift.

            I kinda found this out on Deep Dive on YouTube, which they researched a few studies to make the documentary accurate as possible and making a few assumptions along the way. They said that this sort of process might explain some of the intra-plate volcanism (besides actual hotspots) and that is where they also suggested that some flood basalts might be the result of such mechanism, though to what extent is what I do not know. Like I said, I am making massive, crazy assumptions based on that video.

          • Undara/Mcbride volcanics in northern Australia are also related to deep flat slab subduction, and sound very similar to the early basaltic phase preceding the formation of Paektu as a central volcano.

            Undara is completely unstudied, it was only 5 years ago that it was discovered the place has erupted in the Holocene, even on GVP it is considered extinct. I think Nyamuragira and Nyiragongo are the next flood basalt, but Undara is a second place. Undara has not yet evolved into a tholeiitic volcano, which is something that the nearby Atherton province did, as well as the better known Newer Volcanics in Victoria.

          • Silicic LIPs are formed mostly from when large amounts of basalt try to erupt through a continent and melting it. Often this is from a subduction zone undergoing slab rollback which allows the mantle above it to decompress and basically act like a mantle plume for a while. This is seen as rifting on the surface, with the New Zealand volcanics being at theur root very similar to Iceland except capped by rhyolite. Klyuchevskaya group might be an example of this process where the silicic stage has not begun yet and the basalt can erupt directly. Masaya could be another example, perhaps a better one actually.

            Rhyolite magma doesnt mix with basalt and is less dense so prevents the basalt erupting, but such a volcano needs a colossal heat source to stay alive, and that is something that really can only come from basaltic magma. Some rhyolite calderas destroy their silicic magma chambers in the climactic eruption and start erupting basalt, that is what happens at Yellowstone, why the Snake River is full of basalt right up to the edge of the park. The fact Yellowstone itself still has had huge rhyolite eruptions after its last VEI 8 probably means it still has another big blast in its future, although not any time soon.

            It is quite fascinating how closely linked the two are. Rhyolite volcanoes are usually only ever found in places with lots of basalt.

          • https://www.frontiersin.org/articles/10.3389/feart.2021.741447/full
            https://www.researchgate.net/publication/228683266_Evaluation_of_different_models_for_the_origin_of_the_Siberian_Traps

            Hopefully, these articles could put a bit of context on the Siberian Traps.

            https://www.researchgate.net/publication/301900704_High_water_content_in_primitive_continental_flood_basalts

            Another article on another flood basalt event that is somewhat related to subduction.

            There are also articles relating to how the Siberian Traps erupted, but many more pertaining to how it is connected to the Permain-Triassic extinction event.

            (Luckily, all of these articles are free to download).

        • @Albert:
          I return to the core problem of the Siberian Traps.
          As long as none of the none-deep plume theories explain the mineral output at the Norilsk-Talnakh Masif we have a problem with those theories.
          Same goes for every theory discarding the minerals found in the Kirunavaara-Malmberget Field.

          Anyway, I digress into our age old discussion on the subject.

          What I wanted to write was that it was a fabulous follow up to the first part.
          And I happily join the corechoir on requesting a Part III: The Coreparty 🙂

          Edit: In regards of the Norilsk-Talnakh Masif we should obviously not talk about how we ended up with Talnakhite deposits formed at 80 degrees inside the lava-tubes during the eruption. Even I am confused about that part.
          1280C magma depositing a mineral that can only form at 80C while the eruption is ongoing? I feel that for once petrochemistry might be wrong somehow.

          • It is an on-going discussion. A problem is that much of the Siberian traps are not exposed at the surface, and it has been suggested that the real centre of the eruption was further west than the known traps formation. That may get around the problem of a lack of surface bulging prior to the eruption: a hot plume should have raised the region by perhaps 1 kilometer or more, but instead there is only evidence for subsidence – implying rifting. Perhaps the inflation was further west. There are some reports that the lava composition changed already early on in the eruption which complicate things further. A recent result is that the increase in CO2 levels in the atmosphere started well before the eruption itself. That again might point at rifting. Mineral content is an important part of the picture, but you have to show that they are ‘primary’. and not ‘secondary’ from remelting of earlier deposits. Siberia has had earlier LIPs

          • Chomp!

            I’ll bite and make an article on the subject, will though obviously need a couple of weeks of reading up first.
            I can explain all of it though, except the Talnakhite… nobody can explain that.

  6. There was a small swarm of quakes in the Blafjoll volcano today, south of Reykjavik. Not sure if it is its own volcano, it might be part of Brennisteinsjoll and is listed as such on GVP, but to me seems to be a largely separate mountain and a neighboring fissure swarm. The eruption in 1000 AD was from this volcano, as was another eruption probably not too long before that which created the older of the two Husfellsbruni flows. It also erupted the extensive Leitinhraun flows which cover the area to the south and flowed north into the boundaries of Reykjavik.

    Not even close to consider an eruption here yet but in the light of what is going on at Reykjanes as a whole this is something to keep watch, it is only the start. An eruption here will be slow and probably quite big, like last year but larger, but not something likely to be directly dangerous. It could though set off a powerful earthquake, enough to do serious damage,

  7. Genuinely feel this is one of the best and most informative pieces that I’ve read on the site. Fantastic job as always, Albert.

    I have a much better understanding of mantle dynamics, composition, and associated anomalies having read (and re-read) this two part article series. And honestly, your analogies and image selection helps so much to make what is otherwise dense, new information “click” in such a way that it becomes understood and absorbed.

    IDK what I’d do without this place, I’ve only been here a year now but “checking VC” is permanently ingrained into my daily regimen.

  8. I assume that this is just a coincidence; but after reading this article discussing something I’d never heard about before: LLSVPs, I just read the cover article in the May 7-13 New Scientist magazine about the same subject (which they called earth blobs). It seems to be a hot topic in geology.

  9. I was rather taken by the circulation over the heated plate. It seemed to me that the cold fluid moving along the hot boundary was dragging (very) hot material along to the rising plume area thus keeping it warmer. Further note the hotter area was quite stable and did not rise (or more specifically rose but mixed with cooler fluid).
    As an idea, its fine, but we are dealing with totally different viscosities, temperature and times, and throwing in a spherical geometry as well. None the less (and given what we see) a similar mechanism seems plausible.
    The ULVZ’s would be gobs of particularly hot core being dragged towards to LLSVP, turning into gobs where the laminar initial flow becomes turbulent.
    Anyone got a supercomputer?

  10. https://www.nature.com/articles/s41467-022-30905-4

    Intresting paper on the La Palma eruption 2021
    The deeper magma that came up as the eruption progressed had very low viscosity one of the lowest ever seen .. as it was a low sillica Basanite. Hawaiis Thoelitic Basalt is just as low in viscosity but its because its high temperatures. La Palma reached 1170 C and with a sillica content of 43% explains the low viscosity

    Most mafic melts that erupts above the ocean have quite low viscosity, but viscosity as low as Hawaii, Iceland, Nyiragongo and La Palma are quite rare among most volcanoes

    • Was always interesting, the lava was almost always a’a texture but the flows were very fast and behaved different from a’a in Hawaii.

      It is not surprising though, the eruption originated at a depth of 40 km and rose to the surface very fast, Fagradalshraun was considered a deep origin and that was only 18 km. That temperatures of over 1200 C and viscosities within an order of magnitude of water were actually measured is new to me though.

    • Fagradals was very fluid close to the vent .. Looking like liquid aluminium even more fluid than Holuhraun.. Fagradals was as fluid as Halema’uma’u at least in the vent itself .. because of high temperatures rather than very low sillica content

      https://m.youtube.com/watch?v=y0d086gFzaE

      https://m.youtube.com/watch?v=kiKJQ0hzyqA

      https://m.youtube.com/watch?v=6fKJ5p_-kM0

      https://m.youtube.com/watch?v=hsQFX7gzE00

      https://m.youtube.com/watch?v=RBeNarQ3moQ

      • There was something that I noticed didnt happen at La Palma compared to at Kilauea or Fagradalshraun. At the latter two the gas content of the magma is not as high overall and it seems not to degas as fast, so the lava becomes like a froth and is prone to splashing everywhere when it flows fast, flow is very turbulent, the surges from fissure 8 looked like a flash flood down a narrow canyon. At La Palma the lava really didnt do that at all, it looked completely degassed where it was visible, while many of the vents didnt erupt lava at all and looked like a blowtorch. It seems the lava could degas very efficiently and quickly, which is probably also a sign of the lower viscosity. Probably a large part of the fluidity of Kilauea (and likely Fagradalshraun too) is because the lake was basically lava froth, the degassed melt probably would still be very fluid but still higher viscosity than La Palma was.That being said we will probably get to test that first hand when the lava lake eventually gets too high and drains out of a flank vent.

        The fluid lava at La Palma looked almost like a metal and the flow was much more laminar, it was almost quiet but moved very fast compared to most flows in Hawaii or Iceland on a comparable gradient. The lava also didnt crust over as quickly, perhaps the thin pahoehoe crust that is quick to form a silvery layer on tholeiite lava instead is more or less transparent in alkaline basalt, so has to get much thicker to become visible and will only really show on lava that has cooled down a lot. Or maybe alkaline lavas really just dont easily form the pahoehoe texture at all unless erupted at a very low rate on flat ground.

      • Highly Alkaline lavas can easly form pahoehoe If the lava is hot and fluid ( most alkaline lavas are rather cool ) and often more viscous than normal subalkaline mafic lavas and therefore prone to Aa formation

        Nyiragongo and Nyiramuragira are both Superalkaline yet forms pahoehoe rather easly because of low viscosity. Caldera fillings of both volcanoes are Beautful example of highly alkaline pahoehoe

        But these highly alkaline magmas Basanites and Nephelinites do lack the silvery shine of fluid Hawaiian flows, instead ultra alkaline pahoehoe is glossy. They also dont form the Peles hairs that fluid Hawaiian and Icelandic basalts have, Probaly because of lack of polymerisation.

        Fagradalshraun and Nyiragongo are about same viscosity.. yet the lavas look very diffrent in surface luster and shine

        Nyiragongo haves kind of glossy pahoehoe without that sillica shine

        • La Palma was though also erupting a lot faster than many effusive eruptions, about twice as fast as Fagradalshraun if not more, the eruption volume was 0.22 km3 in 85 days, where Fagradalshraun was 0.13 km3 in over 120 days. Considering La Palma wasnt a drainout of a shallow magma chamber it was very high effusion rate. Probably the lava was a’a from that factor, more than anything else, it certainly formed a lot of smooth surfaces around the vents and at lava tube skylights.

    • La Palma must have been insanely gas rich as well .. some of the vents where real gas blasters .. ash geysers like jet engines. The Top of the cone had a hole with a Supersonic gas flow 🙂 for weeks.. and Sometimes when a really gas rich batch was rising You got a mafic subplinian eruption. The Island was showered by tephra, and at the same time fluid lava was issuing from a vent at the cones base

    • The article mentions specifically a flow seen on Novermber 18 of last year, where lava was seen to flow down the side of the cone in a series of waves that is only seen in fluids with a very low viscosity.

      Well, here it is 🙂
      https://www.youtube.com/watch?v=OeYjLJ1IQcQ

      I think the only reason the lava was not pahoehoe was because of the high effusion rate and often steep slopes it had to flow down, the average effusion rate was an order of magnitude higher than Fagradalshraun or Pu’u O’o, and the vent itself was both on a steep slope to begin with and rapidly built up a masssive cone before the majority of the effusive stage had begun.

      • Got to thinking–a thinnish, runny magma, no matter how hot it was at the vent, would tend to lose heat quickly (it already was degassed). Maybe that’s what limited the pahoehoe?

        • Possibly, but then one would not expect to see a lot of pahoehoe in Leilani Estates and there is instead an abundance of it. Looking on google earth too, Holuhraun is also largely pahoehoe near the vent, from channel overflows and such. I think it has something to do with the fact tholeiitic basalt is silica saturated, so a thin layer could be prone to form very fast in air, lava really doesnt flow far at all in Hawaii without crusting over, where on La Palma it was clear to see bright incandescent channels flowing in open air for many km without apparently cooling much. There was also not much if any peles hair produced on La Palma either, if I recall. I think the very low SiO2 content of basantite compared to most other basalts (44%) would make it hard to get polymerization on the surface. Combine that with high eruption rate and pahoehoe would really only be expected near vents or sjylights, which does seem to be the case.

          The real question I actually have about this eruption is how typical it actually was. Are all eruptions here superfluid like this? There are a lot of rather obvious lava channels that look like more viscous flows, but then they could have been collapses of the cone that slid downslope rather than primary lava flows. The article mentions that similar highly fluid lava was erupted in 1971 and 1949.

          Also makes one consider the first stage if Lanzarote in 1730. Most of that eruption was pretty slow but the first stage was not, rapidly flooding a quarter of the island in superfluid lava not unlike the topic subject…

      • Highly alkaline lavas can Absoutley form pahoehoe just look at tube feed inflated lava fields of Nyiramuragira close to Kivu lake

        Only diffrence is that souch pahoehoe lack the sillica shine of Hawaiian and Icelandic pahoehoes .. they are glossy instead

        High eruption rates are one reason that La Palma did not produce alot of Pahoehoe, and only produced it close to lava channel overflows, most Alkaline lavas are also not as hot as Congo and therefore haves higher viscosity than normal Thoelitic Basalt

  11. What a great series, Albert!
    Hopefully as Carl said we’ll see a part III shortly?
    Maybe you could touch on the mechanisms related to the “migration” of the earth’s Geomagnetic field in more detail?
    If the Geomagnetic field is generated by convection currents of molten Nickel and Iron in the outer core, then if the Geomagnetic field does one of it’s periodic flip-flops (which occur somewhat randomly and quite rapidly on geologic timescales), does that mean the outer core convection currents have changed as well? If so, then how can that happen on scales of only thousands of years which is how fast the Geomagnetic Field can reverse?
    Or, if the convection currents remain stable, then how/why does the resultant magnetic field remain so volatile…both in strength and polarity?

    • I am now awaiting this article with popcorn on hand. 🙂

      Albert really opened a can of worms here 🙂

      • I thought I’d get to the heart of the matter – and now people want more. O dear. I’ll see what I can do – but probably not this week!

        • That is the problem of writing rock solid articles, it melts the hearts of the readers and they crave more magnetic reading to get attached to.

  12. In related news:
    Teide is a tad happy complete with volcanic earthquakes, tremor-pulses, etcetera.
    We might get a bit of Canarian landscaping.

    • Exciting.. Teide is a large slowly active Basanite – Phonolite volcano thats sitting on a weak Hotspot and on a very slow seafloor. Its been active for more than 20 million years. The historical stratovolcano is mostly composed and capped by blocky flows of Phonolite and Tephrites

      A flank eruption on the South Rift void either form a tephrite cinder cone and Aa flow with supertall strombolian subplinian fountains .. or something more sillic .. pyroclastic opening and later extrusion of Phonolite lava flows. The last eruption was relativly small.
      But historical Phonolite blocky flows have flowed all way to the west coast so coud be problematic If it erupts again: it woud be a disaster in slow motion. There is a huge blocky lava flow levee near El Pinalete that can be followed for 12 km. I guess a Teide lava flow coud look very much like Karangetang .. If its a Phonolite.

      A more mafic teide eruption Will be identical to the first Tephrite lava erupted at La Palma last year.. viscous and violently strombolian. Is the swarm still ongoing ?

      • If it is an eccentric eruption it will probably be very similar to La Palma last year, although likely not nearly so big. It might be a long lived event though, with multiple closely spaced eruptions, there were eruptions in 1704,1705 and 1706, with the last one being on the opposite side of Teide from the other two so that event involved two separate dikes.

        If magma rises under Teide itself though it is quite plausible there wont be an eruption at all, would probably take quite some time to wake up, although an eruption there would probably be quite big in volume when it does happen. The last eruption from Teide itself was over 1000 years ago

    • Teide was lively pre the El Hierro eruption. If that was a magma intrusion, be interesting to know what depth it reached.

  13. https://www.google.com/amp/s/www.nippon.com/en/news/yjj2022061800321/amp/

    Am I reading this right? Could be a bit of fake news, but they only said something about preping for an eruption of Mount Fuji an that the title was there to catch attention.

    Haven’t heard anything about unrest at Fuji as far as I know, so this is a little odd. There was unrest a few years ago, until it was changed to being dormant. I am just posting this because it just caught my eye on my Google newstand and thought it was interesting.

    (I am against news with inaccurate information, but the only thing inaccurate about this is the title).

    • No imminent eruption, it is just an article that they are getting the gear that was suggested that they should have on hand in case an eruption occurs in the future.

      So, nothing really exiting. Sad… 🙂

      • Yeah, pretty much. Mount Fuji is a bit of a anomaly because it is pretty much one of the few stratovolcanoes that erupt straight basalt (it does have an andesitic core, though). It is basically a shield volcano disguised as a stratovolcano.

        It does have a series of cinder cones at a N-S sort of lineament, most of which are strombolian eruptions and perhaps even hawaiian-type eruptions, as it did in 1435 to 1436, when they mentioned there was only flame but no smoke. (I got this from Wikipedia).

        It’s last eruption, the Hoēi eruption in December 16th, 1707, was particularly violent for a basaltic volcano, which led to the formation of Mount Hoēi.

        I predict that, and only if it does and this is an assumption, it would be a flank eruption that forms another cinder cone, similar to what happened at La Palma, perhaps. It would’ve been a sight to see.

        • I think actually quite a lot of stratovolcanoes are basaltic, Etna for example. Subduction zone basalt usually has more water, so even a fluid lava would be more explosive. Alkaline basalt also tends to be more volatile too, even so much that there are mafic ignimbrites of such composition, the gas content is just overall very low in Hawaii and Iceland plume basalt, alkaline basalts can be very different.

  14. Earthquake swarm at Long Valley Caldera, about 54 earthquakes recorded on Volcano Discovery, so probably more than that I’d reckon.

    Probably not volcanic though, they seem very shallow, most seem less than 1km deep.

    • I mean, there has been about 40 years of intrusions and magma flow into the general area, an eruption seems likely in the longer term (next century). Will probably be a basaltic eruption, who knows how big, followed by a small rhyolite eruption at the Mono or Inyo craters as next most likely. No scary big volcanism, more tourism eruptions although maybe not up-close viewing… 🙂

      Would put this place as first pick of when the next eruption in the mainland USA will occur.

      • I reckon Mt. St Helens would erupt before that, in the not too distant future, nothing major just a VEI 0-2.

        If I had to guess a non-Mt.St Helens one my guess would be Mt Hood.

        Possibly Salton Buttes (a really wild suggestion) due to the numerous swarms and it’s position near some dodgy fault systems that could set it off.

        • Probably a good chance, but the Cascades volcanoes tend to erupt with a bit less long term signal, as in if there is a warning it wont be too long before an eruption. Long Valley has been steadily recieving magma for the past few decades, apparently at a rate of 0.1 km3 per decade, and is still ongoing today, it is realistically the volcano in the whole of the mainland US that is most obviously heading towards a next eruption. The last eruptions were in Mono Lake in the early 19th century and at Long Valley proper in the 1400s so the area is not so inactive as many probably think it is, much more active than most of the Cascades for example.

        • Don’t write off the Sisters/Broken Top complex in Oregon either. There has been uplift and quake swarms several times in the last decade. Mt. Adams is considered high risk as well. I live in the PDX metro and Hood, St. Helens and Adams all loom large from my vantage on any sunny day. I pay extra attention due to proximity.

          • Three sisters area is my 3rd, St Helens probably should be the first but I dont think it will erupt so soon after its last eruption. Three sisters area is rather unusual, seems like a hybrid of a Cascade range stratovolcano and a back arc rift volcano like Newberry. The Sisters themselves are stratovolcanoes but most of the volcanism is massive basaltic fissure eruptions, or similarly large lava shields. The eruptions are much more strombolian than Hawaiian though, probably would resemble an Etna eruption only without a central volcano.

    • All very shallow along a line nearly parallel to the rather hazardous and aptly named Hot Creek. Likely some hydrothermal disturbances. I would highly recommend avoiding the Hot Creek thermal features for a while. There have been a few nasty injuries there in the past.

    • It is good to remember that the intrusion is named as “volcanic fluids”, in this case that is not magma.
      Well, at least not shallow intruding magma.
      Instead it is geothermal fluids that are moving causing the earthquakes, uplift and increased activity in the geothermal system.
      The only risk at Long Valley Caldera is a geothermal blowout, not an eruption. At least looking at it short or medium term.

      • Volcanic fluids which are moving at a depth of a few km or less are normally water. Water can move around easily, cause significant inflation and of course may even do something hydrothermal. With underground heat, water is going to circulate just as it does in a kettle. In contrast, magma intrusions will be of order 10 km deep. Fast inflation in large calderas (Yellowstone, Naples, etc) is caused by water. Similarly, deflation in urban or agricultural areas is caused by water extraction. (Except in San Fransisco where apparently the sheer weight of the city is depressing the ground!)

        • I would avoid being categorical about that.
          Many volcanoes have shallow magma reservoirs, and I am currently looking at reflection images of water 9km deep in the crust…

          You need to look at the signals in raw format to be able to see what is what. And even then it is sometimes hard.
          In this case it is in a well known geothermal field, and the USGS has done the analysis and found water as a fluid (well sort of, but that is another can of worms).

          I have found that the hard and fast “rule” about water or magma in various depths is almost inevitably wrong in volcanoes. So, I wait for the answer from the competent authority if I can’t analyse it myself, I always prefer to do that analysis myself though.

          Just as an example, I am sitting analysing two geothermal fields, in one where the magma is at 3km (highest point), but the water runs down on the side of the magma chamber to a depth of 12km…
          That one is in a similar caldera to Long Valley.
          The other has no magma, but water at 12km of sufficient temperature.
          Reality tends to crush hard and fast rules…

          • But reality tends to side with the most likely. You can find magma at a few km, but magma chambers are normally deeper (for reasons of buoyancy) and they are the ones receiving the magma inflow. Water can go very deep (100 km at subduction zones) but water circulating down from the surface will mostly remain in the top kilometers. First guess should follow the likelihoods. Exceptions show up afterwards.

          • Problem is just that data does not seem to conform to this theory…
            Looking at volcanoes it seems like this is a neat theory someone came up with in yon olden days that does not parse with data.

          • Then the volcanoes must be wrong .. they need to be taught how to behave properly

          • I have found that kissing volcanoes have astounding effects. 😉

      • In the case of a geothermal blowout, that is not necessarily much better than an eruption. GeologyHub on youtube recently did a video on some of the xplosion craters at Yellowstone and these are no joke, basically almost borderline VEI 4 just no magma. Unlike a real eruption too these would be pretty much instant, maybe over in a few minutes, and very powerful think a sizable nuke going off… Mary’s Bay crater was made by an explosion that would be probably almost 1 megaton, a 2.5 km wide crater.

        Not sure about Long Valley but if it has similar setting it might be possible. There were some powerful hydrothermal eruptions at the same time as the Inyo craters were last active.

  15. Did you know that Geothermal energy is the cheapest energy available?

    Let us compare with other means of energy production, let us start with the building cost for 3200MW nameplate.
    -Nuclear (Hinckley C, UK), 33 Billion Euro
    -Hydropower, 14.4 Billion Euro
    -Windpower, 4.2 Billion Euro
    -Geothermal Electricity Plant, 4.5 – 6 Billion Euro

    So, Windpower is the cheapest? No, here we need to talk about hours producing instead of ideally produced.
    Windpower have the lowest hours in full production of all four listed means of production. Nuclear also have a lot of downtime, but nothing compared to Windpower. Second best in this regard is Hydropower, very little downtime, and the star of the bunch is Geothermal with 95-98% Uptime per year.

    Nuclear is further hit by other related costs like fuel, waste management, and so on. Over a lifecycle Nuclear power is 30-50 times more expensive than Geothermal.

    If we look at lifespan of a Geothermal plant will operate as long as a Hydropower plant, 50-100 years as standard. Nuclear will operate 30-50 years, and Windpower 20-30 years.

    It gives food for thought.

    • I go for a solar power unit. It has an up-time of 100%, a lifespan of 10 billion years, and construction cost of exactly zero as we happen to have one ready-made nearby. Waste management is included. No wires needed: the connection is remote. Converters are already developed to go from solar power to heat (skin), biofuel (plants) or electricity (sand). What more could you want?

      • Sadly in the UK not a full time goer. To run my house, single old man, pretty frugal, I use 10-15kWh/Day. To power this using battery (say 15kWh) I need about 25m^2 of panels for perhaps 8-9 months of supply. To go further into winter (even adjusting panels to 45 deg) is impractically large. For a household with more washing, cleaning and etc I guess you can double that demand.
        This excludes heating and hot water,
        I suspect a modest wind generator circa 2m diam might extend self sufficiency bettwe in winter if I was even more frugal.
        To heat water and house, even with quite good insulation I would need an awful lot of wood, more than my garden could provide.
        Thermal is fine, if you have handy magma sources or other hot gerothermal conveniently to hand. The UK doesn’t.

        • But look at it differently, if we need 25m2 per person in the UK that would amount to 1500 square kilometers in total. We have 240,000 square kilometers available -not a problem. In fact, just our road network covers an area slightly larger than this, so in principe all we need is solar panels strong enough to drive on. Or if we eat a little bit less meat, we need fewer farm animals, less fodder to feed them – reduce the number of cattle by just 2% would release enough land from growing fodder for the solar farms we would need. It is not a matter of how much area we need for solar panels – it is what else we are using that for. UK domestic roofs won’t be enough, but we do have enough space. (The weather – now that is another thing. Can’t we just move the country?)

          Of course, we need much more energy than just what is provided in electricity. This is an underestimate. But how about floating solar farms? Cover just 0.5% of the oceans with solar panels, and the world is covered for all its energy needs. And you can easily move them to where they are needed, and they could even follow the sun through the year.

          • I am probably consuming below average electricity.
            Also for winter use I should aim for 50m^2 and 25kWh battery just for the electricity.
            Then there is the 1000 L/year to heat my house, say 300 L/person.
            And run my var, and my office, and my goods inwards and ….
            BUT
            As I am sure I have said before a square 270 km on a side in extremadura can provide all the EC (+UK) annual ENERGY needs. Add a bit more for winter and use a proper battery where the component ions are cheap and readily available (eg NaS or maybe Fe2+-Fe3+). and you could probably manage realistically with 300km square.
            Currently PV production is about 170GW/annum.
            Total europe about 2GTOE = 24M GWh ~7000 GW so that’s something like 40 years just for europe…(forgetting replacement every 25 years).

            Mind you painting all roofs white to increase albedo would/should have quite an effect.

          • Yes! It is important to be realistic. Too much of the ‘green’ discussion lacks realism. It is also important to be concerned. The other side of the discussion runs into denial of the climate problems which isn’t helpful either. You mentioned a small wind turbine. That requires a windy site. The average wind should be 5 m/s or so, otherwise you may find that the turbine takes more energy to run than it generates. But we need a complete energy package. Solar as much as possible, wind where feasible, hydro and tidal where appropriate, nuclear for baseload, and once you got 95% covered, it is ok to use gas for the occasional day of calm fog. Energy efficiency is essential. We should not waste energy. In a way, having high energy prices forces people to pay attention. It came too fast, and hurts too many people. But we did know that when energy gets scarce, prices become very unstable and they can suddenly explode.

          • On small wind turbines for dark cloudy and very often windy winter days.
            Well I am using about 12kWh.Day,
            I should get about 6 to 8 ave in winter so I need another say 6kWh. That’s only 250W for 24 hrs, and even 100W would be useful.
            I have a windy spot in a gap between two rows of houses ….
            Yes of course what the climate change lobby wants is astronomically high carbon fuel costs to prevent use, except most activists seem to be retired/unemployed and get hit worst! The idiots thinking it makes one jot of difference whether we drill/frack our own oil/gas (which we can tax heavily) vs buying from saudi (which we can’t) completely miss the point that energy is not driven by supply but demand. Cut demand of carbon (by astronomic prices) does cut consumption.

        • @Albert
          The cost of capturing solar is quite high, and the lifetime of the panels is limited.
          On top of that you need a lot of batteries to cover for the downtime (night).
          And let us not forget that a single steel plant will use up to 1.6GWh to run.
          No, we need giant arsed power plants regardless of having solar as an aid.

          @farmeroz
          I think I might surprise you now.
          UK has a much higher geothermal capacity than Sweden, and still we are gonna build a 600MW (nameplate) geothermal plant here.
          Just tell me how many you want in the UK (arrange the funding), and I will happily come and build a few. We have a very good inkling to where to build.

          • Clearly its a trade secret but its hard to believe we have any significantly hot/large areas to keep a plant going for 30+ years.
            We have a few pretty pathetic hot springs, but they aren’t going to power anything.
            If you know better, now would be a good time to make a pitch to govt.

          • We do know where to build in the UK, but right now we are going for building a deep well “pilot-plant” that is 600MW nameplate here in Sweden, and that will eat a lot of our energy.
            But, rest assured that in the end we will build a couple of UK plants.

            And obviously where is a trade secret.

          • I presume that it involves drilling really deep? I know in some areas (northern Australia is one) that there is significant geothermal because of the amount of uranium in the bedrock, I went swimming in a hot spring south of Darwin a long time ago 🙂 and even though this area has been volcanically dead since before complex life appeared there were springs you could have cooked stuff in.

            In hindsight there was probably quite a lot of radon in the immediate area, maybe not a great idea to swim…

      • I am mildly sceptical.
        Quite a few assumptions in the article is wrong, we can amply drill into hotter stuff than 170C as it is.

        That being said, sooner or later someone will invent a better way of drilling. Problem is just that the oil and gas industry have tried to develop better drilling technology for more than 100 years, and put in billions of dollars into the effort, without succeeding.
        Well, there is partial success, but it is still standard drilling in the end, it is just better used.

        When the miracle technology comes and works well, then we will obviously be there to use that instead of our huge honking drill-towers.

  16. Chiles_Cerro Negro just produced 13,500 quakes last week with increased inflation and Cumbal (a volcano that shares the same fault system) is swarming too. Any ideas on the cause of this swarm?

    • I blame the seismometers. Quantum volcanics: the measurement causes the eruption.

      • The Measurement problem is one of the most fascinating and frustrating topics of quantum physics! That confounding trash can stay out of my volcanology!

      • Then surely you don’t know what the seismometer is reading until you look at it?
        And does the act of reading it cause the quake, or was the quake there already?
        Or is the seismometer quietly sitting there in a state of constant jelly-like activity…?
        Quantum volcanics – the Hekla of geology. 🙂
        (Sorry, off to get some more coffee…)

      • After a very tough day at work, and I find Quantum Volcanics.
        I am now a happy man again 🙂

        • PS What do you think about strydefurther’s more precise/cheaper geomapping tech?

          • I am still waiting to receive the spec sheet of it.
            I want to reserve judgment until I have at least seen that.

            But, in general I agree with the idea that the more you can deploy the better as long as you do not sacrifice sensitivity as counted across the entire survey network.

            If I am happy with the spec sheet I will try out a few, and if they work well we will use them in the end.
            But, generally these are for near surface tomography and not for deep stuff.

          • Day 1 Stryde…

            Looked through their entire website and got only Company Blurb.
            Sent an email requesting a technical specification, got more glorious Company Blurb.
            Sent a letter requesting a real whitepaper.

            In other words, probably just a lot of bullshit.
            Updates as things progress.
            I hate Company Blurb, I want facts.

  17. This question is for Carl and his geothermal projects knowledge.

    What’s your opinion on the new ideas about deep hole drilling with microwaves instead of mechanical means?
    If it works the economics seems fantastic!
    The optimists talk about a 10km deep hole for 500000 dollars.

    • There are at least 3 different technologies being in the making that will “revolutionize” the drilling business.
      And there have been many previously.

      Let me state it like this.
      I wish someone succeeded with something like this in the not to distant future.
      If it worked it would cut costs for a large scale plant in half.

      To not trample on anyones feet I will just state that I am not optimistic that any of the 3 versions I know of will bear fruit, but I wish they did.

      I should probably write an article one day about why it is so hard to replace a regular drill-rig. Drilling is just one part of what the “hole making” must do.

  18. There’s a strange M3.0 right on the Gjálp fissure. No sign of it on any of the nearby drumplots, except the djk station which shows something that looks more like instrument problems. Yet, it is listed with 99.0 quality, which means it has been manually checked and approved.

    Wednesday
    22.06.2022 04:15:26 64.531 -17.359 5.2 km 3.0 99.0 14.6 km SSE of Bárðarbunga

    • Yeah, I was expecting it would have been deleted, but still there. Strange one. The signal was like a ping pong… 😄

      • And another similar signal today. Really large amplitude caused the gain to be adjusted so the Langjökull quake is barely visible on djk, while it really stands out on other Vatnajökull stations. Clearly the djk station is having a bit of a problem at the moment.

        • It looks like djk has an electrical problem. The Langjokul quake is interesting in itself. Right in the centre of the icecap, at the usual 6 km depth. The western rift zone has been quiet since a long time. But is is not dead

  19. All the talk of power plants, one could just put a giant sterling engine at the top of Kilauea, probably an instant megawatt powerplant 🙂

    It is understandable yet frustrating that the residents of Hawaii dont like geothermal, PGV is not really a great plant, and not very safe in the event of an emergency (imagine the 2018 eruption went right through it). But then Kilauea might realistically be the most powerful geothermal source on the entire planet, you dont even have to drill for the magmatic heat it is literally sitting at the surface and basically doesnt ever stop, it seems a great wasted potential…

    • Sterling engines have a low efficiency compared to a steam turbine plant.
      I would definitely not use a sterling engine as the primary in a high enthalpy location.

      It is also good to remember that the locals see their volcanoes as sacred places, and it is in the end up to them to interpret their religion.
      I do though not that in New Zealand things are different where Iwis are active partners to the geothermal industry.
      I think there is a lot to learn in New Zealand on the importance of letting the locals decide how to do it, and then come in as a partner and operator of the plant.

      I would not say that the PGV is unsafe. It meets all the requirements and a bit more. Yes, the location is a bit risky, but in volcanic geothermal most spots are a tad risky.

      Kilauea is not even top ten in regards of geothermal potential. I know which is No 1, but I will keep that to myself since I am waiting for a resource permit for it. 😉

      • Was just a thought experiment, I doubt you could build anything on that lava lake without it causing the crust to founder.

        I am as you know quite familiar with the attitude of not disturbing Pele that the Hawaiians (of all backgrounds I might add) have. Regarding PGV being unsafe it is more due to the presence of a lot of pentane on site. I think it is silly how it was portrayed as an incredibly dangerous ‘chemical’, it is basically the same thing as propane or petrol, which are ubiquitous in that area, but then one would not wisely build an oil distillery or a storage tank upon any rift zone, let alone one that is so active.

        I assume Kilauea is genrally out of yout top 10 because it lacks abundant groundwater? Kilauea is the most powerful single point source of heat out of all volcanoes, going at about 280 MW heat output today on https://www.mirovaweb.it/ and it has been more or less at that level continuously since September. Was going at over 500 MW up to 1 GW back when Pu’u O’o was active and the lava lake formed in 2008.

        • Pentane is often used in a heat-converter before a turbine.
          It is in an internal closed loop and is quite safe as such.
          And even in a catastrophic failure it would not be unduly dangerous compared to many other chemicals.
          And in an eruption it would just burn/cook off.

          Open lava lakes is not a good measuring tool for geothermal power output.
          In this case I meant the total energy value of the entirety of the reservoir within drilling range. Kilauea is not on the top list of that.
          I would also not drill into the top of Kilauea, I would go in sideways at lower altitude with readily available water for rock delamination usage, in other words it would be artificial reservoir.

          • I thought the secondary working fluid in those systems was usually ammonia, the use of pentane at PGV being unusual hence the concern. That being said an ammonia leak in 2018 would have been worse…

            Actually quite surprised Hawaii is not a world leader for geothermal, the Keller well next to Kilauea is always very hot, and the water lake that was there until late 2020 was nearly 80 C and stayed at that temperature the whole time until its destruction. Also, well, the fact the caldera has half filled up with lava again only a few years after it formed.

            Is it because Hawaii is an island and the ocean draws a lot of heat away? Or is it because there are no (or very few) felsic rocks? I know rhyolite has a higher heat capacity than basalt which is why Yellowstone is so hot despite not erupting for millennia.

            Or is the heat reservoir under Mauna Loa and Mauna Kea, greater overall crust thickness and distance from the ocean?

        • Carl. As I understand it there is a problem with steam turbines operating under 100c, which is severe erosion by water droplets. Presumably by transferring heat from steam at say 150c into pentane and 150c pentane allows a cycle without condensation and thus down to perhaps 50c on the cold side.
          Is this the reason for usage of pentane?

      • Actually, without giving away trade secrets is the number one spot an active volcano? 🙂

  20. Just imagine the geothermal potential of a large rocky ”Super Earth” class exoplanet. Internal heating is very much related to planetary size ( mass ) if the body is not tidaly heated…

    The bigger a planet is, the more radioactive heating elements it contains ( for an earthlike compositon) and the bigger it is .. the slower it will cool and retains more heat.

    Larger planets also have smaller the surface area-to-volume ratio and so the less relative area there is to lose heat. This means that the large planets will keep and hold on its internal temperature more easily.. than a small one. The larger a planet is the more potential for geological activity. ..as it cools slower

    Earth is the largest terestrial body in our solar system and reach 6000 C in the center, Even a small Super Earth with 2 Earth masses will have a wastly greater internal heating potential.

    I can just imagine a Super Earth type exoplanet with 10 Earth masses and 2X Earth gravity How much internal heating it woud have. Perhaps the really large Super Earths are volcano worlds that have great difficultty of cooling down. With interiors so hot their cores are entirely liquid

    The moderate size Super Earths have only 1,3 Earths gravity for ( 4 Earth masses ) so woud be very habitable for humans if it had Earthlike biosphere…

    In other worlds .. the Aliens .. coud be competely Geothermal.. able to use the massive stores of energy inside their Super Earths. Even a planet sligthly larger than Earth will have a huge geothermal potential

    • Well the surface of a huge Super Earth may look like Iceland and Hawaii all over .. geothermal springs everywhere
      Souch worlds woud take a long time to leave the late hadean like geological phase .. because their massive internal heat production

      Perhaps souch a huge rocky world woud be more like an IO / Venus than anything Earthly

    • Souch planets for me ..
      ( If they are not totaly covered in water )

      Brings only one thing in my mind

      Volcanoes absoultely everywhere!

    • The largest rocky extraterestrial object found so far is an object of 40 earth masses I think: ( core of a gas giant thats stripped ) So basicaly a rocky object the size of Neptune.. is that a magma giant?
      I have no idea really what really gigantic rocky objects woud be like… more than they are very very hot.

      • Kepler 277 b is a confirmed silicate/iron planet with a mass of 87 Earths. Basically a terrestrial planet the same mass as Saturn. It is also not alone, the star has a second planet on a slightly longer orbit that is also terrestrial and 64 Earth masses. Both if these were discovered with the transit method so their radius and mass are known with accuracy, these things are very real 🙂

        There is also PSR J1719−1438 b, which is as massive as Jupiter but only slightly bigger than Neptune in radius, basically the stripped core of a star not unlike the Sun and which is now a solid piece of diamond.

      • Also in theory an iron planet can be more massive than the Sun abd still be basically the same thing. Only once it collapses into a black hole, which might be only at giant star masses.

    • 87 Earth masses and rock and metal?!
      Wow .. Whats the core temperature of that one then!? Many Tens of thousands of degrees C ? Maybe the entire planet is a magma ball … !

      • According the exoplanet catalog, the mass is reported as 64.2(+18.1-15.5) earth masses. What you are quoting is in fact the upper limit, and it could be as low as 39 earth masses. And a second paper using more data finds a very large uncertainty in the mass. We have to consider this as uncertain.

    • https://www.hou.usra.edu/meetings/lpsc2020/pdf/1055.pdf

      Looks like Kepler 227b is like a Mega Mercury in structure ..and we are really talking about insane internal temperatures. I wonder If that core is liquid or solid .. at 87 Earth masses .. But its going to be extremely hot in the center. I never seen an exoplanet like this before .. thats competely astonishing ( suprising. ) that souch thing like that exist .. wow

      Probaly is superhot liquid iron plasma in center .. givning it an insanely strong magnetosphere

      • The universe is a big place, our galaxy is a really big place too.
        If it can exist chances are it will exist.

    • Imagine the depth of atmosphere and energy required to get into a low orbit from these planets.
      Without doing the sums I would bet no chemical rocket could ever do this.
      Which may be why space faring civilisations are uncommon. You do not just need life, you also need a low surface gravity with a thin atmosphere able to support like for perhaps a billion years.
      These situations may be rare.

      • On Earth, these rockets were developed for military purposes, based on the ‘need’ to hit targets on the other side of the world. Without that starting gun, we would have take a very long time to get in to low earth orbit. So perhaps you should add the requirement that the civilization should not be too peaceful

  21. Thursday
    23.06.2022 22:12:06 64.650 -20.340 3.7 km 4.6 99.0 13.8 km S of Eiríksjökull

    • Yeah, seems to be a bit of a swarm happening under Prestahnukur, around 56 earthquakes so far where this one occured.

  22. I had thought the volcanic winter of 536AD was mostly settled as being caused by the Tierra Blanca Joven eruption.

    I was just reading once again about this severe climate excursion and was surprised that it was even sharper and more severe than what occurred after Tambora, and apparently there were multiple large eruptions in the span of 15-20 years.

    Still, TBJ seems small to effect a 2.4C downturn in temps. It seems Harvard researchers suggested it was a “cataclysmic Icelandic eruption” in a paper I haven’t been able to access, and others stated it was potentially a North American Volcano (Alaska, I would assume?)

    Anyone aware of the latest thoughts / findings about this? I’m confused over what Icelandic or North American volcanoes they think are potentially responsible for this.

    • Our thoughts are in https://www.volcanocafe.org/apocalypse/ . The two specific volcanoes remain under discussion, however we know one was northern hemisphere and one was tropical. Ilopango remains the best candidate for the tropical one. Iceland I think is very unlikely for the northern one. The Aleutians is the most plausible location. One paper re-dated the Ilopango eruption to a century earlier but that seems open for argument. The climate impact is not just based on size: it also depends on sulfur content of the ejecta, and in case of multiple eruptions the spacings.

  23. Chiles-Cerro negro has had almost 30,000 earth quakes this month so far, and we’ve had no explanation for what is causing the swarm to begin with! None of the previous swarms have start of with this intensity and this swarm has already beaten the 2018-2020 swarm’s peak intensity. Either Satan shagging some demons or God cleaning his basement could be the cause of the quakes for all we know.

  24. Albert, Thank you for these two fascinating articles. I enjoyed the word play and humor (as always). The illustrations and videos that you chose to include were really helpful, too.

    An aside: Dr. Who is not in my cultural reference set, but I’m looking forward to adding it someday.

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