The bizarre Miocene volcanoes of Germany: Vogelsberg, Urach, and Kaiserstuhl

Some days ago I got into a rather enthralling conversation about weird magma types. It revolved around a particular kind of magma called nephelinite. Some of you may know about this magma variety. Or perhaps not. It is after all a word that doesn’t show up as frequently as basalt or rhyolite. If this name ever shows up here it is probably because of the somewhat disproportionate passion that a few commenters of this blog, including myself, feel towards it. Nephelinite belongs to a family of rare magmas, such as carbonatites and kimberlites. Their composition is very different from that of what is considered to be a “normal mantle”. Something that makes them even more interesting is that they make up a tiny fraction of our the Earth’s whole volume of volcanic rocks. In fact they are the rarest of them all.

Presently this rare family of magmas is being erupted mostly from the East African Rift: the nephelinite lava lake of Nyiragongo, the carbonatite lava flows of Ol Doinyo Lengai, or the kimberlite tuff cones of the Igwisi Hills. What few may know is that during the Miocene southwest Germany turned into a haven of such rare volcanism, in what is a basalt-andesite-rhyolite dominated planet. This is the story of those rare volcanoes from the past. But first let’s have the geologic context.

The European Cenozoic Rift System

Why are there volcanoes in Germany? I won’t go into this question because it is a complicated one. I could write a book about such a question. There are many similar volcanoes in unexpected locations of the planet, mysterious and unexplained. But let me at least point out that these volcanoes seem to be part of a large band of “recent volcanic activity” that runs from Romania, with the Ciomadul dome complex, then across Hungary, Slovakia, Czechia, Germany, France, Spain, to finally reach Morocco. I would place the end of this volcanic group in northern Morocco, where the possibly active Oulmes and Azrou volcanic fields are located.

These volcanoes are spatially linked to a series of rifts that together make up the so called European Cenozoic Rift System. This structure is seismically active today. The map below shows its various segments, most of which are associated to volcanic activity. The rift we are interested in is the Upper Rhine Graben, the URG.


Map displaying the structure of the European rift system. LG=Limagne Graben, BG=Bresse Graben, URG=Upper Rhine Graben, LRG=Lower Rhine Graben, HG=Hessian Grabens and EG=Eger Graben. Source is Wikimedia, original image can be found here.



The largest volcano of Central Europe is the Vogelsberg volcano, located within the Upper Rhine Graben. This volcano is mostly made up of basaltic lava flows, which piled up to a thickness of up to 800 meters, making a shield volcano with a diameter of ~50 km. The total erupted volume is 600 km3.  The activity of Vogelsberg lasted from 10 to 20 Ma (millions of years ago), but the most intense phase was between 15 and 18 Ma. Eruptions would have been very infrequent. Dormancies may have taken centuries, thousands, or even tens of thousands of years. Each eruption would have formed a new vent and produced lava flows. The largest flows may have been long-lasting, taking years to grow, and comprised large volumes >1 km3. This description comes from comparing with other younger volcanic fields in Eastern Australia, and in Arabia, that resemble Vogelsberg, both in chemistry and morphology.


Topographic map of the Vogelsberg Mountains. Image is from Wikimedia and can be found here.

The chemistry of Vogelsberg lavas is not unusual when you look individually at the types of rocks that it has erupted. However when taken all together Vogelsberg comprises a fantastic suite of lavas spanning much of the “primitive lava spectrum”.  What do I mean by primitive? One of the basic concepts relating to volcanoes is the idea of fractional crystallization. Magma can stall within intrusions during its ascent towards the surface, rather than erupting directly from the mantle. It is here that fractional crystallization happens. Magma will gradually lower its temperature and as this happens crystals will grow in the melt. The crystals will sink away. This process will take away certain elements contained in the magma, changing the composition of the residual melt, which in turn will keep moving upwards and maybe fractionating further. Magma types like rhyolite, trachyte, or phonolite are the culmination of certain fractional crystallization series.

The lavas erupted from Vogelsberg are mainly tholeiite basalts, alkali basalts and basanites. All of them are primitive. No significant fractional crystallization has taken place in their ascent. Thus primitive. As such the variety of magmas that have been supplied to the volcano is remarkable.

Tholeiites are the most common primitive lavas erupted in planet, and that includes almost all the lava that is erupted from mid-ocean ridges, where most volcanism takes place. Alkali basalts and basanites get increasingly rare. It is said that they are more alkaline. Alkalinity is an important concept when it comes to volcanism. Tholeiites would be least alkaline, followed by alkali basalts, and then basanites. The next step after basanite would be melilitite, followed by kimberlite. You can see all this magma/lava classes in the diagram below, which is called a TAS diagram.

This is called a TAS diagram, it stands for Total Alkali Silica. It classifies volcanic rocks according to their SiO2, Na2O, and K2O contents. Source is Wikimedia, original image can be found here.



At the same time as Vogelsberg was erupting, a small volcanic field developed 235 kilometres to the south. 350 small volcanoes erupted here between 16-17 Ma. The town of Bad Urach stands nowadays within the center of this ancient volcanic field. Because of this the volcano is known as Urach. It might seem like a small non-important volcano at first sight, but if you look at the lavas you will see something different. Urach erupts melilitite. Melilitites are very rare, alkaline, silica-undersaturated lavas. Actually normally I would say Urach erupts nephelinite, but since I’m writing an article I should be technically correct. Nephelinite and Melilitite might reside within the same area in a TAS diagram but I’m sure there are important mineralogical differences between the two.

Location of the three main volcanoes discussed in the article within the area of the Upper Rhine Graben. Topography from

“Rocks in the alkaline magma series are distinguished from rocks in the subalkaline tholeiitic and calc-alkaline magma series by their high content of alkali metal oxides (K2O plus Na2O) relative to silica (SiO2).”

This is a quote taken from Wikipedia. I think it is a poor definition of what alkalinity really means, not what definitions say, but what you actually see when you plot the data yourself. A primitive magma gets more alkaline when it has less silicon and aluminium, and more of practically every other element which is present in the magma (there are a lot of them). Each different type of primitive magma is going to give rise to a different fractional crytallization series. The crystallization series of basanite could be said to be more alkaline than the crystallization series of basalt, because basanite is more alkaline than basalt. The following are examples of crystallization series:

Tholeiite basalt > Basaltic andesite > Andesite > Dacite > Rhyolite

Basanite > Tephrite > Tephriphonolite > Phonotephrite > Phonolite

But some magma types are so rare they don’t ever seem to make a crystallization series. It was about 10,000 years ago, in a remote corner of Tanzania, that a dike rose to the surface making three small tuff cones: the Igwisi Hills. The eruption was tiny. It probably didn’t last more than a few days. And yet it ejected what is probably the single-most weirdest lava composition ever to have erupted in the entire Quaternary period, at least as far as we know. The most silica-undersaturated kind of lava, a kimberlite.

This plot shows Vogelsberg, Urach, and Igwisi Hills. Vogelsberg erupts what corresponds roughly to the entire “typical” range of primitive lavas, from basalts to basanites. Urach has an extreme lava composition. Igwisi Hills is the extreme among the extreme. The following plot shows the average of magnesium oxide+calcium oxide, versus the average of silica+aluminium oxide. The more magnesium and more calcium a lava has, which relates to it being more alkaline, the less silica and aluminium it has.

So how would the eruption of such silica undersaturated magmas look like? One may recall that less silica means more fluidity. Within molten rock the atoms of silicon will bond with oxygen making silica tetrahedra, aluminium will behave similarly, occupying the same place as silicon in the tetrahedra. These silica tetrahedra will link up to make polymers. More polymers means higher viscosity. That is why aluminium and silicon control the viscosity of magmas. Here are the average silica (SiO2), and aluminum oxide (Al2O3) contents in lavas from the volcanoes discussed:

Vogelsberg (tholeiite end member): 54 wt% SiO2, 14.3 wt% Al2O3.

Vogelsberg (basanite end member): 40.5 wt% SiO2, 12.8 wt% Al2O3.

Urach melilitite: 35.8 wt% SiO2, 8.1 wt% Al2O3.

Igwisi Hills kimberlite: 20.9 wt% SiO2, 3.2 wt% Al2O3.

It is usually claimed that tholeiitic basalts like those from Hawaii, or Galapagos, or the Mid-Atlantic Ridge, are silica-poor and thus fluid. In reality they are near the silica-rich end of primitive lavas; they are more or less are in the middle of the whole silica spectrum of lava compositions. There are many myths in geology textbooks. Of course textbooks like to put things simple. I like things complicated. A lava from Urach should be more fluid than lavas from Hawaii, as long as other factors such as temperature stay similar, which I don’t think are too different, particularly with La Palma’s 2021 basanite eruption having had the same temperature as Kilauea’s tholeiite. Mid-ocean ridges might be somewhat hotter though, if certain numbers from Fagradalsfjall I’ve seen claimed are to be given credibility.

But there is yet another textbook misconception I want to destroy. Fluid magmas are less explosive right? In some ways yes, but in others not. Below are amounts of water and carbon dioxide, the most abundant magmatic gasses, from different magmas in order of increasing alkalinity as reported in various scientific articles. All of the articles are quoted near the end of this post. Volatile contents are difficult to measure so there is a substantial spread in data:

East Pacific Rise tholeiite (Siqueiros fault): 0.037–0.122 wt% H2O, 0.0044-0.0244 wt% CO2.

Mauna Loa, Hawaii, tholeiite: 0.09-0.87 wt% H2O, 0-0.021 wt% CO2.

El Hierro basanite: 0.4–3.0 wt.% H2O, 0.006-0.34 wt CO2.

Ol Doinyo Lengai nephelinite: 0.7-10.1 wt% H2O,  2.7-8.7 wt% CO2

You may observe that gas content increases substantially as magmas grow more alkaline. Tholeiites are very poor in volatiles. That makes tholeiites relatively unexplosive, producing little tephra when they erupt. However the gas content increases by about two orders of magnitude when reaching highly silica-undersaturated magmas.

Melilitites and kimberlites seem to almost always be associated with diatremes/maars. This is also the case of Urach. Maars consist of large explosion craters, sometimes as much as 3 km across, surrounded by a low ring of ejecta. Sometimes the crater is inundated with water. It has long been thought that maars were formed because magma interacted with groundwater leading to large steam-driven explosions. But now there is evidence that melilitite has enough magmatic gas of its own to blow open a maar without any help from groundwater. These are the so-called dry maars. Such dry maars have been recently documented around Ol Doinyo Lengai, and in the Calatrava Volcanic Field of Spain. This has been a known mechanism of kimberlites. Now it appears that a lot of maars previously attributed to groundwater interaction may actually have to do with magmatic-gas-driven explosions of melilitite magmas. In fact I think it might eventually turn out that the majority of maars are “dry maars”.

One proposed dry maar crater next to Ol Doinyo Lengai. it is 800 meters wide and 100 meters deep

Highly silica-undersaturated magmas are very explosive, although they lack the huge scale of silicic magmas like rhyolite or dacite. Viscous magmas such as rhyolite require very wide conduits to erupt, due to their high viscosity, say a 100 meter wide pipe, at least. There will be a lot more magma that can come up a 100 meter rhyolite pipe than through a 1 meter basalt, basanite, or melilitite pipe. Because of this, rhyolites, and other highly silicic magmas, are capable of erupting a lot in a very short amount of time. It leads to spectacular vulcanian explosions, lateral blasts, long distance pyroclastic flows, and powerful plinian eruptions. However rhyolites might actually fall behind fluid highly silica-undersaturated magmas in terms of gas content. That gas is key in shaping melilitite eruptions like those of Urach.

The Urach volcanic field is largely eroded, but one can imagine how it would have looked like when it was active, by looking at present analogues, like those in the Albertine Rift, or Tanzania. Eruptions must have been short and small, mostly lasting from hours to a few days. VEI numbers would have been 2-3. Some weaker eruptions may have produced columns of ash and small tuff cones. More powerful eruptions would have blown away the bedrock, making craters up to more than 100 meters deep. Ash surges would have swept out from these craters destroying vegetation and killing animals. The very high magma gas content would put any witnesses in a particularly severe risk to die from suffocation.

The closest present day analogues to Urach are probably the Katwe-Kikorongo and Bunyaruguru volcanic fields on the Albertine Rift. If one had stood at Urach, 17 Ma ago, the landscape may have been similar. Craters on top of craters. Mainly explosive tuff on the ground. Numerous vents would be flooded with water, making maars.

Katwe-Kikorongo and Bunyaruguru are two small active melilitite volcanic fields in the Albertine Rift of Uganda. They are composed of about a hundred overlapping maar craters each. Urach would have probably been a very similar volcano.



While Vogelsberg stood at the northern end of the Upper Rhine Graben, and Urach was an off-rift volcano, yet a third volcano was also erupting at the same time from the southern end of the UPR. It was an stratovolcano, known as Kaiserstuhl. The activity of the volcano lasted 18-16 Ma. It was contemporaneous with the peak activity of Vogelsberg, and the formation of Urach. Kaisertuhl was the European version of Ol Doinyo Lengai. It erupted a great variety of evolved lavas, including nephelinites, tephrites, phonotephrites, and phonolites, as well as rare carbonatite magmas.

Eroded remnants of the Kaiserstuhl stratovolcano. Image from wikimedia, can be found here.

I have mentioned Ol Doinyo Lengai several times already. This is an inordinate one because it is the only presently erupting carbonatite volcano on the planet (possibly there might be other occasional carbonatite eruptors in the EARS, I haven’t looked up at every single one of them, yet).

Carbonatites are odd magmas. At Ol Doinyo Lengai such lavas are black during the day, they glow deep-red at night, and turn white when solidifying. Carbonatites can remain molten to temperatures as low as 650ºC, so they loose the daytime glow, and are more fluid than silicate lavas.

Frozen carbonatite lava. In Ol Doinyo Lengai. Image can be found on Wikimedia.

There is much evidence that carbonatite is formed from nephelinite. As nephelinite cools and crystallizes in upper level storage it increases in carbon dioxide until reaching saturation, then the melt partitions into two liquids, a carbonate liquid, and a silicate liquid, each being immiscible with the other. Some elements like calcium or phosphorus go mainly into the carbonatite melt. Other elements like silicon, aluminium or iron stay mainly in the silicate melt.

The Kaiserstuhl stratovolcano, now heavily eroded, would have originally stood more than 1 kilometre above its surroundings as a symmetrical cone of ash and lava. The main magma fractionation series was basanite>tephrite>tephriphonolite>phonotephrite>phonolite, all of which were erupted by Kaiserstuhl. This series constructed most of the volcano. Likely it was formed through a combination of lava flows and subplinian eruptions emitted from a long-lived conduit system in the center of the volcano. It’s way most stratovolcanoes are built. Minor magmas include nephelinite/melilitites, and carbonatites, probably belonging to a separate series of more silica undersaturated magmas.

Ol Doinyo Lengai volcano. Image can be found on Wikimedia.

In this sense it is similar to Ol Doinyo Lengai which is known to have gone through three phases of distinct composition. Ol Doinyo Lengai grew to its present height from phonolite tephra and lava. One side of the cone later collapsed and filled with a younger cone of nephelinite. Presently it erupts both carbonatite and nephelinite. This third phase only constitutes a minor mantling on top of the cone. During historical times it has either produced low spattering of carbonatite in its summit crater, with occasional flows reaching outside the crater and sweeping down the flanks. Or it has erupted nephelinite explosively, sometimes sending black ash plumes to an altitude of 15-17 km and generating pyroclastic flows down the vertiginous slopes of the cone.

Kaiserstuhl would as far as we know have erupted similarly. It contains beds of teardrop shaped carbonatite. Teardrops, known as Pele’s tears, would have formed from carbonatites being sprayed into the air as fountains. The heart of Kaiserstuhl makes up a large cylindrical carbonatite intrusion that covers an area of 1 km2. I find this large intrusion enigmatic. The way it was formed is enigmatic. Somehow the magma ate away the walls of the central conduit and turned it into an enormous mass of carbonatite. This is not rare for stratovolcanoes though. One wonders however if it was all molten at once or if it was formed incrementally. Carbonatite also made dikes ranging from less than 1 centimeter in width up to 1 meter. Those dikes likely fed outbursts of carbonatite lava from the flanks of the stratovolcano.


Concluding remarks

Taken together, Vogelsberg and Urach display much of the spectrum of primitive lavas that can be erupted on Earth. Urach has rare silica-undersaturated lavas that possibly led to a style of volcanism somewhat linked to kimberlites, or as close as you can get without erupting an actual kimberlite. Kaiserstuhl is one of the best studied examples of carbonatite volcanism in the world. These three volcanoes, that were contemporaneously active, within and near the Upper Rhine Graben, make up an unusual volcanic episode that is interesting to study.

It will be hard to match the peculiarities of the Rhine rift volcanoes, but I will be writing a few other upcoming articles about European volcanoes. You may find that the European continent has some surprising examples of volcanic activity. Both extinct and active.



Ol Doinyo Lengai:

Discussion on maars that are driven by magmatic gasses

Sources of magma volatile data:

VC articles mentioning the general regions, but covering different topics

The Basel earthquakes

Laacher See


Igwisi Hills

145 thoughts on “The bizarre Miocene volcanoes of Germany: Vogelsberg, Urach, and Kaiserstuhl

  1. Thank you Hector! Really nicely Done

    I Myself Will soon finish my own article about Nyiragongo..

    Will be handed in in comming days

    Indeed magmas are highly complex fluids
    Many highly alkaline magmas Maybe very sillica poor But temperatures are important as well. La Palmas deep Basanites where very fluid because of the combination of low Sio2 and High Temperatures. Many of the most ultra alkaline eruptions are direct mantle eruptions and probaly quite hot

    The Lengai Nephelinite is not extraodinary hot because its stoored in a shallow stoorage system and is probaly quite Etnean Looking If it erupted

    • Thanks Jesper! An article from you is sure to have a unique touch, and always love to read about Nyiragongo.

      As for Lengai’s nephelinite I’m not sure how it would look like. It is hard to tell because whenever Lengai erupts nephelinite it blows to ash from the high gas content. I wouldn’t be surprised however if it was as fluid as Nyiragongo’s degassed nephelinite. Both magmas plot in the same spot of the TAS diagram, having both undergone shallow storage and differentiation. The way the erupt though is like night and day, but that’s due to other factors like plumbing, or the likely older, more aged, system of Lengai.

    • Lengais Nephelinites barely go above 1000 C in most models .. ( 1060 C ) in some models … it will be quite mobile because of its low Sio2 content.. But being below 1100 C will probaly give it a higher viscosity than Kilaūea and Nyiragongo.. Magmas are highly temperature depending also for viscosity

    • Wow these old german volcanoes are insane stuff with Sio2 down to 20% ! I never knew that sillicate magmas coud get that very undersaturated in sillica

      If souch truely primitive Nephelinite and Melinilites erupted at around 1170 C …. then They woud have a viscosity much lower than a normal Thoelitic Basalt melt .. extraodinary rare stuff that we will never see erupt in our lifetime

    • The lava flows on Etna are a lot cooler than the magma. Probably all of the effusive eruptions are from magma sitting in the upper conduits and cooling. The most powerful paroxysms involve temperatures about the same as seen from La Palma and Hawaii, and everywhere with lava that isnt like toothpaste. I think the ashy look is the same as my idea for La Palma, a very fluid gas rich magma that sprays out, basically atomizing itself, far from being a viscous magma. Of course flying a km through the atnosphere it will cool, so the lava flows actually are viscous afterwards. Etna also erupts at much higher rate and has no shallow storage, so no time to degas the fresh magma outside of it actually erupting.

      There probably have been times when Etna was able to host lava lakes and fluid eruptions. Given the natural progression of open conduits it may well create such a lake soon, at least one of the 3-4 open conduits. SEC is by far the most open now, seems the best bet.

      • The first magma from La Palma where not extraodinary low in viscosity as it was a Tephrite .. very Etnean the first weeks .. it was followed later by hotter and more primitive Basanite

        The Basanite at La Palma was so extraodinary gas rich it had a pyroclastic geyser at one vent and gentle very fluid effusion at another

        You Maybe right.. Etna coud be much hotter at its depth and Etnas first lavas 500 000 years ago where Thoelitic Basalts .. I guess melting below Etna at current is deeper now and of smaller ammounts

        • Actually, I found some great footage of the start of the eruption in La Palma, the lava was fluid and free flowing right from day one. The difference is that there was also a lot more gas and the efficient conduits had not yet formed so the fountaining was much more intense and along the whole fissure rather than just the upper part.


        • Also I have started to realise, lower percentage of partial melting doesnt necessarily mean weaker melt source. Hawaii is of course a very powerful heat source and has tholeiitic basalts, but so does Gakkel ridge, which is very slow, so slow it created a silicic caldera in the deep sea. Nyamuragira is maybe the second most productive of all volcanoes and it is as alkaline as La Palma.
          Alkaline magmas probably can form in huge amounts if there is a deep heat source that can erupt, like a continent that is starting to break up. I dont actually know if we should expect a traps event from Virunga now after the recent discussions but I think some massive scale volcanism could happen, like it did along the Kenya rift in the middle-late Miocene.

      • There is HUGE massive degassing at Bocca Nouva now! I never seen souch a sulfur gas plume before from any other volcano ( check Guide Vulcanologiche Nord ) s FB page. Quite Impressive

        You Maybe right .. Etna is perhaps about to form a summit lava lake, formation of souch will be seismicaly silent with Open conduits. Etna is givning off crazy ammounts of gas from a New vent at the summit now

      • The current Etna summit activity does look alot like Nyiramuragiras degassing pits .. I wonder whats happening

      • You are probaly right about Etnas lava that it cools alot in the conduits

        Most Etnean alkaline basalts are quite viscous ( can be as as Viscous as Heimeay but most sits somewhere between Heimeay and Piton in viscosity) But I also read that Etna is rather crystal rich as well in its magma and the pure glass melt between the crystals have a relativly low viscosity.

        There are two cases I seen hot fluid Etnean lava … the First Paroxysm of 2021 had very fluid flows and the summit eruptions of the 2000 s also had some very fluid action with nice pahoehoes … so thats probaly the deep magma

        Etna can Absoutley have a lava lake, it haves the open conduits and the constant supply for that .. Erebus that is MUCH more viscous than Etna haves a lava lake.. so Etna with lower viscosity should have ability To have it as well

        • Etna has about 20% vol crystals. It also often erupts somewhat evolved lavas like tephrites or phonotephrites, So it is not really primitive stuff as in the later part of La Palma eruption.

      • The lava from Etnas summit can be fluid and hot .. as far as I know Etna is an Alkali Basalt at 46% Sio2 .. similar to Hualalai just a bit more Sio2 in it

        • Apparently trachybasalts. My comment above was mistaken. The magma has probably undergone a little differentiation. In a certain way is like Kilauea or Mauna Loa, that also erupt evolved magma, however the difference with the primitive melt is minuscule because the evolution is very subtle. Of course in terms of alkalinity they are not the same. Although in the past Etna did erupt more tholeiitic lavas.

        • Aaa that explains it… Etna is sligthly evolved as an Alkaline Basalt

  2. After looking at some videis from La Palma it looks like the fountains made a lot of ash, but it looks more like an atomized liquid than a powder. Viscous magma would basically act like a solid at the sort of conditions of an eruption, or a non newtonian fluid. As such it would be expected to shatter. But a really fluid magma that is high in gas would be blown into tiny droplets just like happens to water in a jet nozzle. The end result is the same sort of thing but very different start.

    I think Nyiragongo is effusive today because it has got a wide conduit, there is no opportunity to build pressure. It also stops high eruption rates, Nyiragongo has quite a low filling rate compared to Kilauea for example although it seems variable. The fact it is a stratovolcano means it was probably much more violent once, before it formed a wide conduit. It may well turn into a shield now over time like Pu’u O’o did.

    • Thats right .. Alkaline lavas are insanely gas rich. The more alkaline They are the more cO2 enriched They get

    • Exactly.. changes to Nyiragongos degassing is why its effusive now
      Its steep shape was formed by violent paroxysmal episodes with same composition

    • I guess a similar mechanism ought to be involved at Mt. Erebus with its phonolite lava lake too then.

    • Yes, those are some interesting questions. There is however a general misconception though in what drives explosivity. Fluid magmas don’t really loose their gas so easily, sometimes they do have lava lakes like Nyiragongo which are permanently under convection and degas the melt. Otherwise they erupt with their gas, The thing is that tholeiite basalt has almost no gas compared to other magmas and that is really why volcanoes like Kilauea or Piton de la Fournaise have such tame eruptions. Other fluid magmas can have high levels of gas and have no problem in building steep cones.

      • A stratovolcano is basically a polygenetic cinder cone. We have seen many basaltic cinder cones, from small ones up to huge ones like Pu’u O’o. Then there are borderline cases like the SEC at Etna. Nyiragongo is basically a giant version of Pu’u O’o, it was allowed to grow for millennia before finally losing its narrow conduit. Looking at Pu’u O’o also gives a clue to how unstable the mountain could be, if the lake ever gets to overflow then a sector collapse is not impossible, which could be quite a disaster. I think eventually Nyiragongo will become a shield but its transition will not be smooth or well behaved. And all it takes is for the wide conduit to be destroyed and it could turn into a lava geyser again.

  3. Thank you, Héctor! That was a really interesting read. Strange to think of volcanoes so close to Britain!

    • Thanks Clive, it is the closest active volcanic province to Britain (Eifel which is near Vogelsberg). Britain does have many extinct volcanoes though and hopefully one day I can cover those too.

  4. Thanks a lot for this article! You are answering a lot of my questions about the volcanoes near Strasbourg!

    • Thanks Rémi. That whole area has had an interesting volcanic past. I’m glad that this article can help other people understand the volcanoes of SW Germany, which have few modern-day equivalents.

  5. Very nice Héctor!
    Thanks much for the article, looking foward!

  6. Thank you Hector for this terrific compilation of data and your interpretations. As often is the case here on VC, I learn about stuff I never knew even existed.
    One thing I’d like to hear your take on, is the possible role that rapid rejuvenation processes could have had on crystallization/recrystallization and the mass differentiation/stratification of magma in storage? In this theory, magma stored at depth is “cold” (relatively) and largely un-eruptable until a sudden pulse of heat/bubbles rise from below and rapidly heats the shallower magma to a point where it can erupt. This process of magma rejuvenation is indeed rapid, theorized to take place over the course of only decades instead of millenia. At present, a similar process is believed to be taking place under Chile’s Laguna del Maule volcano, which is continuing to exhibit the fastest rate of uplift anywhere on the planet as an emplaced sill about 5km down undergoes an episode of rapid heating (or so the theory goes).

    Also, what about the variable pressure/temperature effects on stored magma caused by the forming and retreat of past glacial ice sheets? The theory of crustal elastic rebound is well known…which directly shows that the crust is pliable…thus pressure at depth changes as the surface weight ebbs and wanes. Depending on the intrinsic thickness of the upper crust, or the thickness of the ice sheet, this process of extra surface weight creating higher pressure and temperature at depth would be more/less pronounced…hence different rates/types of crystallization over time for a given magma reservoir could vary place-to-place.
    It would seem to me that the timing between magma emplacement at depth and the presence/absence of an ice sheet overhead would create different conditions for further magma evolution as the surface conditions change?
    i.e. if magma emplacement takes place with a glacier above, then the magma would experience a period of decompression later on once the ice thins/disappears.
    Conversely, if magma emplacement takes place with no ice on the surface, then that magma would undergo compression during the next ice age: thus a different evolutionary process of the magma would in play than if it went through a period of decompression.

    • Thanks Craig Heden!

      I used to be more enthusiastic about the idea of cold mushes underlying volcanoes and being rejuvenated, mostly because it seems to be an increasingly popular model. There is a wealth of scientific publication supporting this model.

      However what I’ve read on fossil magma intrusions and chambers tends to support more a model where magma chambers are largely liquid and crystals settle down to the bottom of the chamber where they make solid cumulates and are deposited in layers resembling sedimentary formations. I’m referring to layered intrusions like Bushveld, Skaergaard or the Scotland volcanoes. Bushveld for example deposited its famous layers of chromitite. Changing conditions in the Bushveld magma chamber are thought to have at times favoured the crystallization of chromite which then sank to the bottom and was deposited simultaneously across the entire extent of the massive 300 km wide magma body.

      In this alternative view crystal mushes would be restricted to narrow conduits of stratovolcano systems where crystals cannot settle. Many stratovolcano systems are known to erupt phenocrystal contents of up to 40-50 % vol. This is the view I favour now.

      • Thank you very much Hector for your thoughts!
        The liquid vs. mush (or cold) magma chambers is a recurrent theme on VC…and this latest installment is very much on-point.
        I would note that the heavier crystals likely do not form instantaneously…and probably take centuries or longer to grow large enough for stratification to evolve.
        That in turn requires a very stable, low viscosity environment (chamber) devoid of any convection or heat input from below? But, how a magma chamber could retain enough heat to maintain it’s low viscosity without new heat input from below (which would destabilize a liquid magma chamber through convection) I don’t have an answer.
        That’s why I asked about possible changes in temperature of a magma chamber as a function of pressure increase/decrease from surface ice intermittently pressing down from the surface?
        It would seem to me that the increased pressure would both raise the intrinsic temperature and therefore alter the crystallization and differentiation process(s), but the increased pressure also inhibits phase change between solid and liquid that’s needed for stratification.
        So simply put, what would you expect would happen to stored magma when subjected to varying pressure from above, given everything else being equal.

        • Wouldn’t this be partially the cause for many of the large eruptions in Alaska and the Cascades during the Holocene, since the end of the last stadial?

          IE destabilizing pressure changes from isostatic rebound.

  7. Thanks for the read.

    I’m rather fascinated to learn about how this magma is so potentially explosive. I think that leads to another link in the area of Doinyo that may explain the caldera formations just south of the Ol Doinyo Lengai itself, and potentially speak to its possible future.

    See the image here – Note Lengai and its maar formations, that as Hector points out are in large part a product of the explosive nature of this primitive magma.

    Now note just to the south, the series of very large calderas, that in many ways, look more like extraordinarily large maars as opposed to traditional collapse caldera structures. The most famous of these is the beautiful Ngorongoro Crater.

    I’m speculating here, but I think that we **may** have a scenario where the maar type formation behavior may actually scale to very large size as well as the more common small sized maar formation.

    • Right Alkaline magmas are very gas rich .. even a mildly alkaline magma is very much more cO2 enriched than a normal Icelandic or Hawaiian basalt

      An superalkaline magmas like Nephelinites and Melinilites are real cO2 gas bombs .. and explains why Nyiragongo have pumped Lake Kivu full of gas. Superalkaline magmas can have a cO2 content thats 100 s of times higher than normal basalts

      • The relationship between alkaline magmas and carbon dioxide is fascinating. Alkaline magmas are richer in almost all elements except silica and aluminium, this includes volatiles, but particularly carbon dioxide. If we compare Lengai’s nephelinite with East Pacific Rise tholeiite we find that nephelinite has 12 times the amount of sulphur, 80 times the water, and 360 times the carbon dioxide that tholeiite has. Carbon might the element that alkaline magmas are the most enriched of. Because of this highly silica undersaturated magmas probably need to shed away the carbon somehow. Nephelinite sends away its carbon into a carbonatite melt. Kimberlite crystallizes its carbon into diamonds. Also alkaline volcanoes might affect the climate more strongly due to their high S content when there is a major plinian or caldera forming event,

        Regarding Ngorongoro, it certainly does need better research. It does seem like one of the oddest caldera clusters in the world, and I would love to know if nephelinite ignimbrites are possible.

        • There is basically 0 information on Ngorongoro, other than that it is a volcano. I just assumed it was an evolved volcano maybe once like Kilimanjaro that self destructed. But now given the area and the way these magmas erupt it might well be something else…

          Is ignimbrite really a good word to describe here? Or maybe rather is such a deposit actually the same sort of thing as a rhyolitic ignimbrite? It would seem that for such a fluid melt even if erupted explosively that when it fell back it would turn into lava, sort of like fog condensing, and that seems to be a thing that is actually important in geology. Most of these primitive lavas seem to be quite hot, Nyiragongo is consistently given a temperature range comparable to Hawaii, maybe a bit less on average but sometimes actually higher, very wide range. Still, it is not the barely incandescent temperatures that rhyolite erupts at.

          I dont really know how realistic it is to get a maar the size of Ngorongoro. I think only asteroids can make explosions that big so deep in the crust. But certainly that caldera must have been an apocalyptic event, and right in our neck of the woods at the time too.

          • Tholeiities merge back into lava when thrown into fountains but that is because they have not been properly fragmented, they make large, maybe can happen even with basanite. However if you go to the maars and tuff cones around Ol Doinyo Lengai what you see is that the melilitite was blown to ash, no lavas are visible, the fragmentation was generally too intense for lava flows. In fact I expect the fragmentation is probably much more intense than with rhyolites. In rhyolitic eruptions one usually finds pumice lapilli and bombs close to the vent, usually lapilli-dominated deposits. In melilitite maars the deposits usually consist of fine ash, although it is also possible to see lapilli and bombs. Maars generally have ash-dominated deposits indicative of stronger fragmentation.

          • That is a maar though, a smallis volume very powerful explosion. An ignimbrite involves a huge volume of magma, and it is all probably ejected so fast it cant get away from the ground so goes sideways instead.

          • I expect in a lot of cases if you factor in the scale of the event an ignimbrite is less explosive than a maar. There might be exceptions like at Hunga Tonga but then that has a good chance to have been partly hydrothermal, it was in the ocean after all. Maybe volcanoes like that are combined ignimbrite+maar.

            Also what of the hydrothermal explosion craters at Yellowstone? No new magma but some were of rather huge scale, VEI 4-5 equivalent power.

    • This would be a bit of odd thing to think about but…

      Alternative Vernshot eruptions?

      • *Possibly. It could’ve been a big explosion or a odd caldera-forming process. That is all I could think of.

  8. Volcanism is far from done in this area of Europe.
    Africa still pushes north.
    Wouldn’t be surprised to see another few eruptions from Vogelsberg area within the next 2000 years or so.

  9. Speaking of CO2 in certain lavas, has any recent papers come out regarding the dissolution of carbon into the magma melt bodies, at the mantle lithosphere interface? I think we are going to find out that dissolved carbon does more than we realize.

  10. The eruptions on Lanzarote began with eruptions of nephelinite too, the first flow in 1730 was a fast eruption that flooded a huge area within only 2-3 days. Apparently the eruption began basically without immediate warning. Eruptions within the first two months were rather powerful and included both significant explosive eruptions and a lot of lava. One of the cones even self destructed and blew its side out all the way to the ocean before erupting a flood of lava then stopping after only a few days. Later eruptions which produced the majority of the lava were much more passive, and less alkaline, probably would have closely resembled Pu’u O’o or Fagradalshraun, but the event began in quite a spectacular fashion.

  11. I handed in my Nyiragongo Article!

    I wants it Improved and not cropped
    I only allows it to be published under my name 😉 all Photos and photographer credits haves to be added in as well .. the boring text needs the Photos

    • I allow massive improvment of the text
      And add and Re – write .. But only allows it to be published under my name

      No cropping or splitting in the article
      I woud like improvement of the text

      All the Photos and and photo credits and GIF s haves To be added in .. They keep the text fun and alive 🙂

      Im not a geologist .. so best for experts To check If its accurate

      • The editors will be very happy and grateful to be allowed to work on your article.

    • Its meant as a single post

      I allow the Dragons to work on the text Improve it .. make it better and more readable …

      Im acually not good at writing texts

      But it will be fun

    • The Photos are important .. I also cerdited the photographers.. including a GIF … They haves To be taken in

      Without them … this text Will die

      I allow massive improvment of the text
      And Making it more readable yet even deeper .. all up to the dragons now

  12. Really excellent work Hector! Tremendously informative and interesting piece you’ve put together. I also want to give a shout-out to Chad, Jesper, Albert, and you again Hector for the fascinating comment chains going back to the previous article debating Iceland’s classification as well as magma chemistry / fractionalization in general.

    Speaking of, I have some questions. Conceptually I comprehend a great deal about geology and volcanology, but there are a few aspects of magma chemistry and magma’s behavior in volcanic systems that elude me.

    I hadn’t realized there were multiple magma series, I only thought the “series” was basalt to rhyolite and all of the intermediary steps. I didn’t realize there was an ultramafic starting point that could lead up to phonolite. And on that point, what is it that determines the “series” or progression that a certain type of magma must adhere to? In other words, basanite can’t evolve into rhyolite, or can it under the right conditions? Is it the starting point that dictates the potential end point, or more the conditions the magma is exposed to in the sill / dyke / conduit? And silicic magmas are more likely to form in a “magma chamber” where the melt is exposed to granitic underlying rocks as it incorporates those particulates into it, yes? So more direct pathways from mantle to the surface normally equal more mafic end products?

    And lastly, just to make sure I have this correct:

    Rhyolite is explosive because of its extreme viscosity, likely clogging the volcanic conduit and building immense pressures.

    Ultramafic magmas are explosive more in the fashion of maars as they contain a higher gas / volatile content.

    Can Rhyolite be gas rich, and does that influence it’s behavior? Similarly can ultramafic magmas be gas poor? Is that an inherent aspect of their chemistry or dependent upon the available venting of the volcanic system containing them?

    And lastly, since Basalt is truly the least explosive on either end, what allows basaltic volcanoes to eventually erupt violently / explosively? The presence of ground water that -did not- come from the magma itself? That would be my working understanding.

    Sorry I know this is a lot of specific questions mixed with a lot of rambling, but I’m really trying to wrap my mind around all of these concepts.

    Love you guys!

    • Ultrabasic is a better defenition 🙂 But some of these superalkaline magmas can be ultramafic as well .. If mgo content is high enough

    • They can be both gas rich and gas poor ( A ryholite lava dome ) or Degassed flows from Nyiragongo

      But gas content goes up with alkali content

    • Had one other main question.

      So there are essentially two versions of basalt -> rhyolite, tholeiitic and calc alkaline? Reading the Wikipedia articles on this I feel just confuses me further.

      I comprehend the differences in chemistry between tholeiitic basalt -> rhyolite and its calc alkaline version, but are there practical differences in terms of their behavior in volcanic systems?

      Not having actual university level education on this subject means I’m learning in a more fragmented way which I think is leaving some gaps in my understanding. I definitely feel I should grab a textbook or two here.

      I don’t expect anyone to answer every individual question, just wanted to type this out and absorb any general responses.

      Thanks again!

      • Depends How alkaline it is
        A really low sillica Basanite does not turn into a Ryholite it turns into a Phonolite as it gets old and stale

        And really really insanely Alkaline magmas are perhaps produced in souch small ammounts and are so Sio2 undersaturated that they dont have a Sio2 rich offspring

      • Also no formal geology education 🙂

        I think tholeiite basalt is chemically reduced, where calc-alkaline is more oxidised. What that really means is iron in tholeiite is Fe2+ and iron in CA basalt is Fe3+, which is why lava goes rust-coloured in Hawaii, and also sometimes have hydrogen flames (Fe2+ reacting with water at that temperature) Calc-alkaline is also made by hydration melting, where tholeiite is from decompression melting under high temperature. Hekla is a patch of hydration melting which is why it is weird among Iceland volcanoes which are otherwise tholeiite volcanoes. Most subduction volcanoes also erupt calc-alkaline series which is why Hekla sometimes resembles one. Both tholeiite and calc-alkaline basalt are made from high degrees of partial melting.
        Alkali basalt is formed by lower degrees of melting usually deeper. Vatnafjoll next to Hekla erupts this, even though they share the same patch of crust and are maybe connected deeper down, they have separate magma with different origins. Katla also erupts alkali basalt, and so does Etna. I think properly this rock is called trachybasalt, or sometimes hawaiite, with there also being trachyandesite and then trachyte. If you go more alkaline still then you get basantite and that series, although the end point of that (phonolite) is more like andesite than rhyolite, not enough SiO2. That is as far as I know anything about but there are definitely more.

        I have seen a hypothesis that mantle plumes are generated by subducted crust reacting with the outer core, actually chemically reacting not mixing. This is especially relevant is very deep and hot plumes like Hawaii.

      • For a good all around look at geology and volcanology in general, I recommend Global Tectonics 3rd Ed.

        If you grit your teeth and pay attention, it will discuss triple junction stability and evolution.

    • Kilauea is explosive in part because of groundwater and probably also because of caldera collapses allowing for very rapid degassing that would not usually happen. If the collapse in 2018 was larger (say fissure 8 was further east or below sea level) then the ring fault might have actually erupted, and because all the magma was draining out the caldera was a place of low pressure and the remaining magma higher in volatiles, the roof falls down and it all blasts out, reset and repeat… Also likely hydrothermal eruption/maar formation in 1790 at the same time as the other mechanism.

      In Iceland I think all explosive basaltic eruptions are because of water interaction. Veidivotn eruptions would be like Laki or Holuhraun but there was apparently a massive lake there before 1477 that was filled in. Future eruptions there will be more effusive most likely. Grimsvotn is obviously subglacial but also has a deep lake in its caldera. Laki was violent when fissures first opened but the dike was probably quite wide to allow for such a big eruption, so maybe this is to be expected and also a rare exception, otherwise the magma was typical tholeiite basalt probably exactly the same as at Holuhraun. I imagine komatiite lava probably is not so explosive either, maybe even less than basalt, probably flowed silently out of the source vent.

      I presume basically any basaltic volcano with a large shallow chamber can be explosive under the right conditions. Decompressing a magma chamber is the same regardless.

      Have also looked at a lot of rhyolite volcanoes, I dont actually know if rhyolite is the most viscous magma. It is obviously not flowing like basalt, but soda lime glass is basically synthetic rhyolite and flows fairly easily. There are also alot of examples of quite extensive rhyolite flows, like at Medicine Lake and Newberry volcanoes, or at Puyehue Cordon Caulle, those flows look much more mobile than the lava domes on Merapi which are apparently basaltic andesite… I guess though obsidian implies crystal poor lava, so maybe crystal rich rhyolite is a different story.

      • Soda glass is an alkaline syntetic ryholite

        Glass furnaces is also at around 1300 C and that lowers the viscosity alot and the alkalinity as well ( the sodium lime )

        • Right so heat is as big a factor in viscosity as silica content / polymerization?

          Makes sense. So a cooler tholeiitic rhyolite would be the most naturally explosive variant, mechanically speaking?

        • Yes temperatures does alot .. Althrough low Sio2 helps alot too specialy If its very low

          The best is a combination

          But yes temperatures does alot as well ( almost as much as Sio2 )

      • The alkalinity of Soda glass Maybe helping To lower its viscosity as well .. as alkaline bindnings are less polymerized

        Real Quartz Glass is a difftent matter .. nearly Impossible to melt .. over 1700 C is required

      • Very informative musings and exactly the sort of thing I was looking for to help me contextualize this stuff.

        So a lot the explosive element of basalt aside from external water interaction seems to come from mechanical forcings, which makes a ton of sense.

        Thanks Chad.

      • It took me a while to see how decompression can make things happen quite explosively. It was actually an amazing talk by Donald Dingwell that finally clued me in. I love that people were able to re-create these mechanisms in the lab!! Outrageously dangerous and fun – a pocket volcano!

        The whole video is awesome, but particularly the section after about 40 minutes.

        • …and then there’s this more recent work done in Buffalo, NY (that hotbed of volcanism) where they injected water into fluid melts in a variety of ways.

          I mean, I love glassworking, but adding explosions to the mix?!? That is a fantastically terrible idea and I desperately want to be involved.

    • Thanks Ryan.

      As far as I’ve seen the series the magma follows depends on its starting composition. For a given starting composition the magma will follow a particular series. However there are 2 complications to this rule. First, different regions of the world can have slightly distinct starting compositions and series which they follow. Italy is a tremendous oddity in this sense. Italy has trachybasalts, and phonotephrites as primitive magmas, which everywhere else in the world are magmas obtained through crystal fractionation.

      The other complication is that when magmas get too silicic they will usually invade the field of other series by taking a sharp turn. For example a basanite that has evolved into a phonolite, if it continues evolving, it will turn more steeply towards more silica rich compositions. From observation I think this happens when the most ready to crystallize major elements run out, like magnesium and calcium, so the other stuff starts to crystallize away, like sodium or potassium. That way many magmas belonging to the basanite-phonotephrite-phonolite series end up in the trachyte field, intersecting with other series.

      See samples from the Nabro Range in Afar. Magma starts as alkali basalt, and then evolves towards trachyte, however it finally takes the turn into rhyolite intersecting the field of magmas that crystal-fractionate from tholeiite basalt.


        • Perfectly answered one of my main questions, I think a lot of this is starting to click finally!

      • Regarding the explosivity, what makes rhyolite so dangerous is, above all, its elevated eruption rates and volumes. Note that to carry rhyolite, or crystal rich dacite or andesite, because of their enormous viscosity, you need conduit at least ~100 meters wide for it to fit. Basalts generally use conduits 1-2 meters wide, and basanites and melilitites are, if anything, smaller than that. That is why for a similar ascent rate, rhyolites are expected to produce an eruption rate ~1000 times superior to a basalt. One should also consider that due to this high viscosity individual rhyolite intrusions are going to be much more voluminous, eventually building magma chambers bigger than basaltic ones. Also the high viscosity leads to the formation of voluminous cryptodomes and lava domes. If a cryptodome suddenly decompresses you get a Saint Helens-like blast where a VEI 4 happens in the matter of seconds or minutes. If a dome collapses it is also an enormous volume of lava that you are instantly sending airborne and is capable of dealing far-reaching damage. So what makes the rhyolite dangerous is not the viscosity itself, but the larger volumes and eruption rates that this viscosity favours.

        • Rhyolite is also gas rich. As magma crystallizes volatiles tend to build up in the remaining melt. I don’t think they are as gas rich as melilitites and nephelinites. The volatile content of magmas is very very difficult to measure, because it tries to escape the magma.

          • I downloaded mineral inclusion data from Taupo Volcanic Zone rhyolites and Ol Doinyo Lengai nephelinites, from GEOROC. Because inclusions contain gas trapped within minerals they are thought to better represent the original volatile contents of a magma. There was no sulphur data for the TVZ. One set of Ol Doinyo Lengai inclusions gave much higher volatile data than the other, even though both were inclusions in nepheline crystals, not sure why. Ol Doinyo Lengai nephelinites are overall much more gassy than TVZ rhyolites. The exception is water though, were the TVZ is slightly richer. In facts looks like the TVZ is almost solely water-driven.

            Taupo Volcanic Zone rhyolite: 4.3 %wt H2O, 0.014 wt% CO2, 0.034 wt% F, 0.093 wt% Cl

            Ol Doinyo Lengai: 3.4 wt% H2O, 16.9 wt% CO2, 3.14 wt% F, 0.79 wt% Cl.

          • Ol Doinyo Lengai has a lot of fluoride, surprising it isnt poisoning the local area, 3% by weight. It has more fluoride alone than the entire percentage of volatiles of most other magmas.

          • When reading the GVP content on Ol Doinyo Lengai, I encountered several reports of chemical burns on people during nephelinite eruptions. I did wonder if it was due to the hydrogen fluoride.

          • Ol Doinyo Lengai is more volatile rich than primitive melilitites, though. As expected from a melt that is more evolved. I managed to find volatile data from Katunga (Uganda), the same primitive magma as Urach. There were no CO2 and H2O for Katunga though. The average gas contents go as follows compared to the East Pacific Rise tholeiites (all are inclusion data):

            Ol Doinyo Lengai: 3.14 wt% F, 0.79 wt% Cl, 0.6 wt% S.
            Katunga: 1.01 wt% F, 0.39 wt% Cl, 0.24 % S.
            East Pacific Rise: 0.01 wt% F, 0.009 wt% Cl, 0.097 % S.

            Ol Doinyo Lengai: 3.4 wt% H2O, 16.9 wt% CO2
            East Pacific Rise: 0.12 wt% H2O, 0.046 wt% CO2

          • It seems alkaline magmas also have an enormous fluorine enrichment relative to tholeiite, the F enrichment is probably of a similar magnitude to the carbon enrichment.

          • I would expect if such burns were from HF it would be taken much more seriously, HF has this reputation as being a very corossive substance but it isnt really, but your body treats it like water and it goes straight into your bones and also sucks calcium out of your blood… It does cause tissue damage like other acids but that is not really a hazard compared to any other acid, actually hydrofluoric acid is pretty weak compared to HCl.

            Because HF is a weak acid though NaF is not neutral like NaCl, it is a base, which is more appropriate given that I think an acid gas would not last long in such an alkaline environment. There is also a literal lake of drain cleaner next to Lengai. I think chemical burns would be from something in that part of the pH spectrum rather than an acid.

      • Thank you so much, Hector, again!

        This article and comment chain going back has done so much to increase my understanding and knowledge, so much appreciated!

  13. Since we are talking about magmatic compositions, I would talk about something much more primitive and hotter than the others described: komatiite. Komatiites are pretty much the hottest, densest, and one of the fastest lavas on Earth. The lava itself has the viscosity of canola oil and has temperatures in excess of 1600 degrees Celsius and denser than obsidian (it’s viscosity probably second to only Ol Doinyo Lengai’s natrocarbonates). It has been talked about but maybe no one has talked about its properties. (old paper, I know. Maybe the only one discussing its properties as far as I know.)

    The lava itself is unique. Some lavas, like basalt, could thermally erode the rock underneath under certain conditions (temperature-wise), but komatiite will nearly always thermally erode any sort of rock and, even though only a lava flow, can “absorb” the rock it has melted, inducing something along the lines of contamination into the lava flow itself. In fact, according to the paper, after one week, it would burrow to 25 meters near the vent.

    The lava is maybe fluid and hot enough to have a turbulent flow most of the time and maybe the one lava type where a’a lava flows are rare and sheet flows are common. Of course, their formative process requires a mantle 400 degrees Celsius hotter than it is now, which was commonplace before 2.5 billion years ago. The last time that this type of lava erupted of the sorts was on Gorgona Island, perhaps the last gasp of this type of lava.

    • But is isn’t the only one that erupted at the time, perhaps hotter than the Gorgona lavas.

      These lavas (the Tortugal lavas) in Costa Rica are perhaps hotter than the lavas previously mentioned, if not, maybe on par with the ones in Karoo. The origin of these lavas during the time is more tied to the Galapagos hotspot, whereas the Gorgona ones are of a mid-ocean ridge. This proves that komatiites could maybe erupt again, but very unlikely as these sorts of conditions could only exist at a few times.

      Hawaii could be a candidate, but the plate moves too fast. Iceland could be another, but the heat is too spread out (I think). It is perhaps that sometime in the future that they may erupt again.

    • *not obsidian, basalt. My brain screwed up a little bit there.

    • Exactly .. but thats an ultramafic lava and not an ultrabasic lava

      Komatites can have Sio2 over 50% and zero alkali content

      Their high temperatures makes it flow like liquid iron

      • I know, komatiite isn’t a ultrabasic lava but a ultramafic instead, but I am quite interested in the ultramafic as I am interested ultrabasic. The komatiites are perhaps the only magma that is truly ultramafic. Ultrabasic magmas could classify as ultramafic but they are unique as komatiite but they go in the other direction in terms of alkalinity. Either way, both ultrabasic magma and komatiites are perhaps quite fluid as they lack silica, with their origins traced to the mantle.

      • 45-50% SiO2 and over 18% Mg. It is the same composition as olivine basalt except it is entirely liquid and a lot hotter.

        Hawaii does have samples that are a very similar composition though, even today. It isnt at that temperature but I think at present it is not impossible for komatiite to erupt there. Maybe if Kilauea or Mauna Loa drains out completely there will be nothing left to mix with and such magma could surface. Hualalai might also be able, it is more alkaline but only compared to Kilauea, it is still on the tholeiite series, and has no shallow system.

        • I think it is also often said that komatiite is basically if you actually melt peridotite mantle rock completely. That actually does require 1600 C temperature, I remember reading somewhere that olivine with more Mg means it formed at a higher temperature, some olivine from the 2018 lava at Kilauea was created at over 1300 C within a month of the eruption happening, and yet even at that temperature there were some crystals.

          Related but different, is lava an ionic liquid? I know SiO2 is not an ionic compound but I presume silicates with other metals are, and reportedly there was a NASA experiment to make oxygen and metals from basalt using electrolysis as a way to make material on the Moon. That used powder suspended in molten salt but still.

        • Komatites are much richer in olivine than normal basalt … so rich They form whole crystal massives of that in thicker slowly cooled flows

          But yes souch hot dense magma probaly resides deep under Iceland and Hawaii where the astenosphere is superhot

          • Komatiite is about the same composition as picrite basalt, the difference is that komatiite is actually the whole liquid, where picrite basalt is normal basalt that has lots of extra olivine. It also has slightly more alkaline elements but I dont know if this is particularly significant. If picrite basalt was completely melted it would probably turn into a form of komatiite.

            It is sort of like how the lava of Merapi or St Vincent is basaltic andesite, but it is actually andesite or dacite melt with mafic crystals, which equal out to the same composition as basaltic andesite. Picrite is the same composition as komatiite but it is basalt melt with ultramafic crystals.

          • But, I could imagine what a truly komatiite volcano would look like, even though the last one died out maybe 89 million years ago. Such volcanoes would be really active, while they’d have some of the gentlest slopes of a volcano ever (maybe) with empty channels from other eruptions and plenty of lava tubes, with some being longer than the longest lava tube known.

          • Looks like I got this a bit mixed up… if you read the one at 23:34 before the one at 23:37, it would make sense.

          • I think most komatiite volcanoes would have been on the mid ocean ridge, probably would not be too many such volcanoes on land. I think a komatiite central volcano wouldnt exist, would probably be more a basaltic volcano that is very hot and erupts komatiite in large events. So probably would look like a shield we are familiar with but maybe actual komatiite vents would make very flat shields.

            Also possible is that it was erupted as flood lavas from LIP provinces, in which case there would be no komatiite volcanoes, rather fissure eruptions and lava flows.

            Thing really is that if such a magma ever got stuck on its way up then the magma would cool and olivine would crystalize out rapidly, which would basically turn it into basalt, and because of the low viscosity of both magmas at the relevant temperature this would probably be much faster than magma evolution in other systems. So either a massive heat source was required (plume, LIP) or it had to erupt very fast with nothing stopping it on the way up like at a ridge. I guess a Archean analogue of Iceland would be suitable, where both of those things are present.

            I guess though, Nyiragongo is a central volcano made of a magma that isnt supposed to create central volcanoes, so I presume at least one completely komatiite volcano has existed before 🙂
            We will have to see what Io is like, whether its lava is komatiite or basalt, or a mixture of both.

          • Iceland does sound somewhat similar to the Galapagos event 89 million years ago. Perhaps, all Iceland needs is a ridge that spreads fast that wouldn’t allow the crust to thicken.

          • If it was spreading faster though then Iceland would probably not be an island, at least not a big one. It seems really just very hard to get komatiite to erupt on land in any large amount 🙁

            Really I wonder if komatiite really ever erupted above the ocean, the actual Komati rocks are submarine.


            Pretty much a 211-page study about the cooling and mineralization processes of komatiite at Pyke Hill. The lavas there are, for the most part, deep-water in terms of their formation, perhaps supporting an idea (even though the author probably didn’t mention mid-ocean ridges) that they formed primarily by such mechanism you described.


            Another article I have found but with a really odd detail: komatiitic tuff. Surely, every type of magma has the capability to produce tuff, but I was surprised to find out komatiite can form tuff and ash. (I somehow shouldn’t be). The only way it could happen is by water, and to the least shallow water. It could mean it has formed islands, though not many. Perhaps back in the Archean Era, komatiites where the basalts of that time, forming oceanic crust and maybe even islands (though it would be a bit controversial to think about it).

        • I did note if a comment you made about Kīlauea erupting out a sort of komatiite? The probable closest thing to Kīlauea erupting komatiite in recorded history is the 1959 Kīlauea Iki eruption. As far as I know, there was some video made on it (sort of) where the magma came straight from the mantle, bypassed the magma chambers only to be stopped by a portion of “rift magma”, mixed with it and erupted.

          What if it bypassed that? I think it would more be like on the lines of picrite basalt to komatiitic basalts instead of, well, true komatiite. Still, it would be a site to see. Kīlauea has plenty of time to maybe do that before its source of power wanes.

          • Kilauea and Mauna Loa have both erupted picrite basalt at a temperature where only very few crystals could exist. At Kilauea that was in 1959, where one of the fountains began with lava that was at yellow incandescence, although the other fountains were not unusual relatively. In saying that though, it was widely reported the lava lake before 2018 was as hot as 1250 C. There was also olivine in 2018 that formed at a temperature of over 1300 C not long before the eruption, so the summit storage of Kilauea seems to be far above the liquidus temperature of basalt. This might actually explain some things, the longest flow from Pu’u O’o was about 24 km in 2015, but the summit overflows and Aila’au eruption went over twice that far at apparently the same eruption rate. If that lava started out hotter it would flow further.

            At Mauna Loa in 1859 the lava was a picrite basalt at 1215 C, and like at Kilauea Iki it erupted from a vent that wasnt on the rift zone so presumably bypassed the normal plumbing. That lava went down the flank like a flash flood, into the ocean in a week over 50 km away. There were some other radial eruptions, but all of those seem to have started on a rift, 1859 was almost its own thing entirely.

            There also was something I read that a Mauna Loa sample rock had a calculated eruption temperature of 1650 C, was still basalt but that is right in the range. The plume has been at least that hot for a long time too, 12 million years ago it made the Puhahonu shield which had samples with a similar temperature, even higher. Basically the mantle under Hawaii is as hot as the Archean mantle so it is not exactly unreasonable to see lava of komatiite composition erupt there, but it would be rare.

          • Hmm… that is quite interesting. I kinda want to see the paper about the super-hot Mauna Loa basalts, not because I doubt you but it made me quite curious – how could normal basalts be as hot as komatiite without becoming komatiite themselves?

            That reminds me of another volcano, Wrangell. Somewhat unrelated, but according to what I have heard, it erupted out andesites like as if the are basalts and it is quite a question. How could andesites possibly as hot as basalt act like basalt without a change in their chemistry or even magma mixing?

          • I cant remember exactly where the source for the really hot basalt at Mauna Loa comes from, I think it was posted as a link here but over a year ago.

            It is just temperature, if the lava is crystal poor andesite then it has lost some of its original composition, so making it hotter wont change anything except to lower its viscosity. Same as in Hawaii a lot of the eruptions the lava has already lost its olivine which forms a dense pile of crystals under the magma system. Making the typical composition Hawaiian lava (like at Pu’u O’o for example) 1600 C will only make it change physically, it will not change from being basalt to komatiite. If you get picrite basalt though, that is from when big eruptions can dredge up the olivine, or just after a magma chamber has been destroyed. If you melt picrite basalt at 1600 C then that would probably turn into komatiite, because the overall averaged composition is like that, even though the actual liquid originally was basalt with crystals.

            I guess that would mean the formation of the rock on Mauna Loa was not necessarily a big eruption, because the rock is still basaltic composition despite the temperature, meaning it was not picking up extra olivine. It may have been part of a long lived eruption.

            I am wondering, in the rather unlikely scenario that Pahala actually erupts directly, might that give us the right scenario to erupt komatiite? In some ways it is frustrating that Kilauea resurfaces so often, even things that happened only 1000 years ago are almost hopelessly obscure.

          • This is an older text with a different number, but has some data on the lava of Mauna Loa. It seems though that the lava that was erupted at such a high temperature was submarine, and that such eruptions on land may be very infrequent. It also seems nothing has happened there since Kilauea began forming, Mauna Loa is not dying but is definitely past its peak, while Kilauea is probably going to get more active in the future.
            It is hypothesized that deep intrusions below the volcanoes might ve able to erupt on the submarine rift zones, but are otherwise not really eruptive events or closely related to the volcanism on land.


            That being said, the INSAR data for Kilauea would suggest that not all of the magma that feeds the ERZ comes through the connector conduit, there are at least two sill complexes in the ERZ and possibly as many as 5, and each of those could be considered a full volcano in its own right. They all connect horizontally (2018 showed that) but the ERZ complexes started inflating immediately in 2018 while the summit was silent for over a year. Now the ERZ is also feeding magma back to the summit, even though now the lava lake is at a higher elevation than most of the ERZ. There are new gravity and magnetic data coming out that will help resolve this, the last was in 1978 before Pu’u O’o but already showed magma present in the area it would later form. The magma system is in equilibrium but that doesnt mean it is only fed from depth at a single location.
            I think Hector is much more qualified to answer this question than I am though, much of this is educated speculation 🙂

          • I don’t know that much about komatiites.

            Regarding the InSAR data of Kilauea though, my interpretation was different. I don’t think the ERZ has its own feeding. I don’t even think there is a deep rift anymore. Intrusions at Kilauea have their base in the 2-3 km below the surface range and there is no good evidence for intrusions ever happening deeper than that. There are no long period earthquakes under the East Rift that would indicate vertical rising mama. The horizontal magma tube of the ERZ as shown by seismicity, also runs 2-3 km deep, so it was likely constructed by the shallow intrusions, dikes and sills, creating a structure that helps make dikes more efficiently. The rift slopes outward from the summit at a constant slope, seemingly implying the supply is outward from the summit. After the 2018 eruption what we saw is that sill complexes of the volcano inflated sequentially away from the 2018 eruption site. While the summit magma chamber inflated continuously, see UWEV, from the very end of the 2018 eruption the caldera was inflating.

            Inflation was first strongest in the sill complex near JOKA (Heiheiahulu), but rapidly slowed down. The sill complex east of Pu’u’o’o had started to inflate at the same time as JOKA and kept going at the same rate for much longer. However near the start of 2020 it can be seen that inflation changed from east of Pu’u’o’o to the sill complex west of Pu’u’o’o, changing the motion of JCUZ. The sill complex southwest of the summit had been deflating throughout this time, particularly near its southwest end, and only started to experience strong inflation in the later half of 2020.

          • This is interesting. Looks like, by technicality, Maunaloa used to have a deeper rift where they bypassed the traditional magmatic system of the volcano itself. If it is hot there, that could mean it would’ve been hotter below the summit.

            However, I found another volcano of the same chain that could’ve erupted komatiites.


            Pūhāhonu, the largest true volcano ever confirmed, would’ve possibly at least erupted some komatiites since it is at a stage where the Hawaiian hotspot had a pulse. This proved that the Hawaiian hotspot is special in a way where it never wanes after formation but pulses.

            The study did mention something about the factor of not only a hotspot but also a thinner, younger and warmer crust would’ve been required to build a big volcano like that. The question to that is, as always with the volcano, could it really form komatiites?

          • The ‘deep rift’ is a long standing concept for both Kilauea and Mauna Loa, this paper worked using that. It seems possible this is not a real thing, which Hector presents a reasonable argument for, but then it would be expected that the volcano has grown upwards and the rift followed it, so there would be magma pathways that are deeper. it is either that, or the current setup is a very recent thing that is still in the early stages of formation. Given that the oldest exposed lava shield on Kilauea, Kanenuiohamo, is probably only about 1000 years old and possibly only 750, then possibly the oldest sill complexes in the ERZ are only this old, which is still very recent, probably around the same time the islands were first discovered. The one under Heiheiahulu probably formed in the 18th century, before 1790, though is still active today. The one under Pu’u O’o might have only formed properly since 1955 or even after 1961, but seems at some point to have merged with the existing structures a bit further uprift given the whole of the ERZ deflated in 2018. The storage under the summit is much more established, but the sills going southwest might be a new thing, or not.

            Puhahonu actually formed at a lower growth rate than the Big Island… 🙂
            If Mauna Loa once had the capacity to erupt lava that was at 1650 C then I expect an eruption that hot is still very much a possibility, the mantle cant have cooled down by 400 C in only 100,000 years, especially given that summit eruptions from Kilauea have historically erupted lava that is hotter than that of Mauna Loa. What seems to prevent that (and likely is the same thing in Iceland) is that komatiite is very dense, so probably cant rise to the surface through the basalt, it would need to erupt as a completely separate monogenetic eruption that would basically not be part of either volcano. So you could have basalt that is superheated to the same temperature, and would realistically be physically the same, but the composition would be different.

            If one of the volcanoes though does a complete self destruction and leaves the deep feeder exposed, then there coudl well be an open lava lake of such an extreme temperature… 🙂

      • Really primodial archean Komatites where formed from 2000 C partial melting I think .. and emerged as hot as 1650 C perhaps even much hotter Looking like liquid sunlight and as fluid as iron slag

      • Komatites are extraodinary olivine rich .. forms massive solid crystals formations of pure olivine

        Picrite Basalt is more olivine rich than Thoelitic Ones

        But Komatites haves a very high olivine content and rich in rare metals

        But yes very much like a pure pedriotite melt

  14. Been a while since Kilauea did something different 🙂
    Maybe it was noticed that the lake has been a bit low recently, two big DI cycles nack to back. The ERZ stations have also possibly recorded a change to an abrupt southward movement and also somewhat east. There is no obvious inflation to suggest an intrusion but it looks like the flank has slipped and pressure was taken off the summit.

    Makaopuhi crater:

    Pu’u O’o:

    The summit is largely unchanged but if magma is moving into the ERZ now, even if not at high rate, that is potentially quite significant especially if it is getting as far as Pu’u O’o already or at least has a path to. If the storage further east shows activity I think it would be wise not to buy property in Puna.

    • Nice catch. There may have been a slow slip event of the south flank. SSEs are often periodic happening every ~2 years. It has been more than that since the last one. We will have to wait and see what the GPSs look like.

      • There were three M3 earthquakes at the south flank on July 4. They may relate to the potential SSE..

    • Well that last data point on the cross caldera distance is quite a big change… It looks like a malfunction, but then this plot has been accurate enough to record the DI events, and it survived through 2018 as well as 4 intrusions in the immediate area since then, two erupting. For it to malfunction only now, seems a stretch…

  15. The last one was supposed to be in 2018 I believe, except things got more exiting…
    Not sure if there was also one that happened with the eruption in December 2020, but this might be the first slip since 2018, it is at least the first time a signal like this has happened since eruptions resumed. Will be interesting to see if more magma flows into the rift now, the pressure is not so low as before.

    If one considers the progression of where magma came from in 2018, first from local storage in the LERZ, then Pu’u O’o and Makaopuhi, then the summit storage after fissure 8 opened. When the eruption ended inflation was immediate at the area the dike started from, then at Pu’u O’o after a few more months, and then the summit only after about a year. The next stage now I think will see the summit fill but it will not overflow like I thought before, but instead a new conduit will form on the ERZ at one of the storage locations. As for which one I dont know, but east of Pu’u O’o might be more likely given that Pu’u O’o was formed east of Mauna Ulu. But probably either between just east of Pu’u O’o up to Makaopuhi (maybe even within the crater) or otherwise around Heiheiahulu, which would be much more destructive.

  16. Aside from Ol Doinyo Lengai there’s also Mount Homa in western Kenya that has erupted carbonatites. However Mount Homa doesn’t appear to have been active in the holocene.

    • Yes, Mount Homa is a famous example of a carbonatite volcano. There is an impressive volcanic province west of the Kenya Rift that is made up of nephelinite and carbonatite lavas, and it seems to have built some massive volcanoes. There are several large nephelinite/carbonatite volcanoes including Mount Elgon, Kadam and Napak:

      “The lavas of these three volcanoes consist chiefly of nephelinites and melanephelinites, among which are olivine- and melilite-bearing varieties. Phonolites and trachybasalts, or trachyandesites also occur, usually among the earlier flows. The volcanoes are, however, largely built of pyroclastics, mainly coarse agglomerates, which are mostly composed of fragments of nephelinite”

      Smaller central volcanoes with nephelinites and carbonatites in that area include Moroto, Yelele, Toror, Ruri Hills, Homa Montain, and Kisingiri. Volcanic activity in this area has however long died off. It happened in the Miocene I think.

      Presently Tanzania is probably the main location for carbonatite and nephelinite eruptions in the world. Ol Doinyo Lengai and other nearby less active volcanoes.

      • It seems Napak is 20-18 Ma in age. So they are some of the oldest volcanoes in the Kenya Rift. Probably from the initial Kenya rift formation.

        • Overall the highly alkaline magmas seems most common in the southern end of the rift valley, possibly where they’re most common presently on Earth. However information is sparse and studying and monitoring probably even more so..

  17. Something interesting, and maybe quite profound given the context of this article.

    Kimberlite volcanoes are a lot more scary than I thought, basically a Hunga Tonga but they can happen anywhere and give less than a day of total warning. And that the eruption of such a cluster could basically set off an instant thermal maximum in a year. Might be the singular bit of truth in the myth that volcanoes make more CO2 than us.

    Maybe the clusters are not that intense, maybe Igwisi Hills is showing that each pipe is millennia part, but even at that, we are still looking at a VEI 4-5 that appears out of the blue in a place that volcanoes categorically shouldnt happen.

    • Coud one appear under Stockholm 🙂 ? That woud pulverize the entire city I guess .. Kimberlites are worst form of Maar eruptions.. some form tuff cones so are basicaly insane short plinian eruptions

      Whats the eruption rate of a Kimberlite? Same as Hunga?

    • Hmmmm 🙂 dreams of Stockholm beginning to shake.. and the kimberlite eruption appears right below the subway station

      ( everyone flee )

    • Igwisi Hills Are probaly not really like a true prehistoric Kimberlite blast .. they are so cO2 rich that they blow themselves to dust.. But it coud be one with the gas rich material deposits eroded away leaving just the effusive last stage

      • I imagine that just smaller eruptions leave nothing behind. It would be very unlikely that the only example of kimberlite volcanism was also the only kimberlite volcano ever that wasnt a maar eruption.

        It seems they form on cratons adjacent to rifting, so Sweden is probably safe.

      • The insane fludity of Kimberlites also concentrate the dissolved co2 at the top forming immense gas pressure as it decompress on the way up

        Amazing is the ability to penetrate a more than 250 km thick Craton as some kimberlites can be found near cratonic cores

        • I would guess that kimberlite volcanoes form above a deep complex at the base of the craton or maybe within a rift in the base of the craton. So probably the fact there has been one eruption on the Tanzania craton now which is being stretched, means there will be many more there in the future. It is sort of like how most volcanoes have an extensive shallow system with a few deep conduits, in this case there is deep plumbing of some sort and sometimes dikes race up and blast a hole in the crust.
          In the case of Igwisi Hills maybe this is before the field has properly formed so no maars yet. The maar fields in the rifts might be basically the same but not as deep origin. Maybe kimberlite volcanoes arent actually unusual but because they form in geologically stable areas so are the only part to survive long term.

    • How fluid are Kimberlite lavas ?
      I read them mostly as crystal rich mushes.. with a very low Sio2 Althrough a crystal poor Kimberlite probaly haves extraodinary low viscosity as seen in some papers

      • I doubt the fluidity matters because even if it is as fluid as water the magma is atomized when it erupts. Igwisi hills was not a maar volcano, seems to have actual lava but whether it is a short viscous flow or something like a tiny lava shield is not really clear. Lamproite magma, which is very similar to kimberlite, is always described as erupting as effusive flows of low viscosity or as maar volcanoes.
        There are mid Cenozoic kimberlite volcanoes in the Kimberly region of northwest Australia (name is completely coincidental) which have been described as solidified lava lakes, many of which are exposed as flat mesas because the surroundings eroded, presumably once a cone surrounding the lava. Lava lakes would tend to cool to make crystaline rocks compared to a flow or ash.

        The fact it moves so fast in the dikes and through the crust, I have a hard time believing it is anything other than a very fluid lava, maybe even close to water like carbonatite, maybe it also melts at a relatively low temperature in the same way.

    • kimberlites are small eruptions. And most don’t breach the surface but get stuck just below

      • Not according to the article, they might have a big range but some are rather huge eruptions.

        • I am a bit dubious about the article. Kimberlite eruptions are CO2 driven and have some carbon, but they have a long distance to travel and little of their original content reaches near the surface. If you want a major impact on our climate, these VEI 2’s are not the kind of eruptions you’d try. You would go for a nice Jesperian flood basalt

          • Yes, that is true. The volumes of a kimberlite field are unlikely to be significant enough to impact the climate. Present-day melilitite volcanic fields might be the closest analogues to kimberlites, in that they are also made up of diatremes, erupt from fissures-like fields and have magmas of relatively close composition. Melilitite eruptions doesn’t seem to produce that much ejecta. Maybe VEI 2-3. Even if you have 100 maars that erupt in rapid succession it may only be 1 km3 that they erupt altogether. Let’s say 10 km3 being generous. It would be emitting the carbon dioxide equivalent to 1000 km3 of tholeiite basalt, but it is not that much after all, and likely over a prolonged period of time, since each maar would be formed in a separate eruption. LIPs are much more voluminous than that and form in very short pulses. Individual eruptions and intrusions go well beyond 1000 km3.

            Good evidence would need to be found that kimberlites can erupt significant volumes of magma, or that they erupt in large clusters in a very short timespan.

          • The idea seems more to infer the eruptiosn to be a trigger for the melting of methane clathrate, which is generally considered the cause of the PETM in all studies. It is something that I think should be considered, there are less likely ideas out there. There is also not any reason why one idea being more likely prevents another idea from happening too, there was a LIP going on at about this time and also an impact, all three could have been a part of the equation.

            The study seems to provide evidence that at least some of the pipes were formed together and partly buried each other during the same eruption, and that the volume of magma involved in each pulse of activity is rather a lot more than a VEI 2 just based on tephra volume still in the pipes, let alone what escaped.
            It also seems that even if there is not a lot of magma, that most of the gas within the magma does erupt as the CO2 separates and blasts open the crust in front of the magma as a requirement to create the pipe in the first place, it is what makes the eruption a maar crater after all. So a huge CO2 emission is still plausible in the absence of a large volume of magma erupting.

            Maybe the Lac de Gras kimberlites are an extreme case, the supervolcano of kimberlite volcanism. The comparable young maar fields in the EARZ also as far as I am aware have not erupted historically nor been studied in detail for age pregression, maybe a lot of them did erupt together.

          • Kimberlites do not have the volume to produce gas emissions with anything more than local effects. Clathrates can melt for all kind of reasons, but it requires a major change in the environment. If minor eruptions could do this, our climate woUld be much more unstable than it is. This idea requires strong evidence. Kimberlites are fascinating eruptions. But not world destroyers

          • All Magma can be world-destroyers, you just need enough of it.

          • You could also argue that all continents are build on magma. It also creates, although that is of little comfort to those it destroyed. But a kimberlite sometimes pays us back in diamonds so that is ok

          • As you know I don’t mind the destruction in fact I am looking forward to it. Chiles-cerro negro and/or Taal might deliver on my desires.

    • It is an interesting possibility. Of course this is very theoretical at the present moment.

  18. Overall the highly alkaline magmas seems most common in the southern end of the rift valley, possibly where they’re most common presently on Earth. However information is sparse and studying and monitoring probably even more so..

    • Exactly because They prefer deep melting in a deep astenosphere under high pressure cut generaly gets more alkaline the further south you go into the rift

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