Nyiragongo and its ultra alkaline magma – Part III

Introduction 

In part one I took a close look at the large scale forces that drive volcanism in Africa, at continental rifting in its different stages and the types of magma chemistry that form because of it. I also discussed the origin of the forces that created Nyiragongo and Virunga in the first place. In part two I gave a broad overview of Nyiragongo, how it actually works as a volcano and the behaviour of its activity. I discussed how it got its steep cone despite being fluid and effusive. Here in part three I am getting into even more interesting things, as I will have a look at one of the things that makes Nyiragongo so famous: its magma chemistry.

A quick look at magmatic alkalinity

TAS diagram (TAS stands for Total Alkali Silica). I placed Nyiragongo’s current composition to show what an unusual magma composition the nephelinites of this volcano are, very different from normal basalt. The link is here https://upload.wikimedia.org/wikipedia/commons/thumb/0/0a/Classification_extrusive_rocks_EN.svg/2560px-Classification_extrusive_rocks_EN.svg.png

In magma composition Nyiragongo is almost as alkaline as you can get among silicate magmas. But what is alkalinity in igneous geology? The name is used to describe rocks that contain one or more of the alkali elements: lithium, sodium, potassium, and a few less common ones such as rubidium, with odd atomic numbers and which lose their outer electron rather easily. They are strongly reactive, especially with water, and are never found as pure elements. When a magma is alkaline it contains a lot of sodium, potassium in its mineral SiO2 molecular chains. The more sodium/potassium-rich a magma is, the more alkaline it is. Nyiragongo’s magmas are in other words full of alkali metal ions in the silicate chains rather than ”normal” silica oxides. These alkali metal oxides are mainly sodium oxides and potassium oxides, with sodium silicate oxides being the most common.

Although mineral compounds that have alkaline elements in then are quite common on the Earth’s surface, most magmas are not very rich in these elements. Low silica magmas that are mildly alkaline rich are called alkali basalt and these are quite common. Even more alkaline compositions are called basanites which are much less common. Nyiragongo is almost as alkaline as you can get. They are classified as ”ultra alkaline nephelinites”. The mineral nepheline is an alkali mineral that has chemical bonds with the element sodium in the form of sodium oxide.

Alkaline magmas also have their own evolved silica-rich equivalents. Phonolites and trachytes can be seen as alkali-rich andesites and dacites. Phonolitic Mount Erebus is an example of a volcano that produces very alkaline, silica-rich lava. In the photo below I plotted Nyiragongo’s composition at the red point at arrow, they are ”ultra – alkaline”. They also enrich strongly in other elements than only sodium and potassium. The more deficient a magma is in SiO2, the more concentrated the other elements become in the magma as well, not just sodium. CO2 content also rises rapidly with high alkalinity. The blue area on the left in the diagram are alkaline magmas, while the yellow to the right covers more ”normal” subalkaline magmas.

Alkaline magmas also have their own differentiation like basanite > tephrite > tephriphonolite > phonotephrite > phonolite, meaning that an ultrabasic magma like basanite can differentiate and turn into a phonolite which is the alkaline version of a ryholite. Non-alkaline magmas evolve this way as they get old and stale: tholeiite basalt > basaltic andesite > andesite > dacite > rhyolite. In Erebus a basanite turns into a phonolite as it cools and crystallizes. Mildly alkaline basaltic magmas are common, but basanites, tephrites, phonolites and nephelinites and melilitites are very uncommon. The more alkaline a magma is, the rarer it gets.

The most highly alkaline magmas are nephelinites, melilitites (and kimberlites) and they are also the most rare. They are supercharged with CO2 and enriched in other elements as well like magnesium oxides and ferrous oxides. We can place alkaline unevolved magmas from most common to most uncommon like this: alkaline basalt – basanite – nephelinite – melilitite, with melilitite the most uncommon. The two magmas, melilitite and nephelinite, are SiO2 undersaturated and they don’t really evolve into SiO2-rich forms in stale magma chambers, because there is a lack of SiO2 in these magmas.

Graphic: https://media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs00445-021-01435-6/MediaObjects/445_2021_1435_Fig6_HTML.png Geochemical map over the volcano’s lava composition, all of Nyiragongo’s lavas are in the very silica undersaturated foiditic class, classified as nephelinites because of their richness in nephelinite mineralogy.

As explained, removing the silica from a magma solution will increase the other elements on its expense, and that means that magmas that are as silica undersaturated as Nyiragongo are rich in stuff like phosphorus, potassium and calcium, much richer in that than ”normal” basalts. This means that Nyiragongo’s magmas are extremely fertile when they weather into soil. Africas highly alkaline volcanism are a major reason for the high productivity of African soils and biospheres.

What strange Nephelinite magmas are:

a look at Nyiragongo’s magma composition

Nyiragongo is famous for its very low silica composition. The magmas are indeed very unusual. Here I will try to explain Nyiragongo’s lava composition. I myself also have an interest in highly silica-undersaturated rare magma compositions, and a rock from this volcano is a dream for my rock collection. Nyiragongo’s lavas are the rarest extrusive rocks on Earth together with melilitites, that is one reason why this volcano is so interesting. It is impossible to write an article about this volcano without having a look on its bizarre magma composition.

Image: by GeologyHub youtube channel, this shows Nyiragongo’s extraordinary low silica content compared with other famous volcanoes. While its true that Nyiragongo display very low silica, the speed of the lava flows are mostly because of steep slopes and very very high eruption rates. https://www.youtube.com/watch?v=QuGi3kB7WZg

Nyiragongo has the lowest silica content of all currently erupting silicate magmas on the planet. Magmas are classified according to silicate content. High silicate magmas with 70% silica are felsic. They are sometimes called acidic-like ryholites and ryhodacites. Magmas with a bit lower silicate content, 68% to 60% are called intermediate magmas, such as dacites and andesites. Low silica magmas, 46% to 50%, are called ”mafic” or ”basic”. Such magmas are often basaltic. Rare magmas with even lower silica, 36% to 45% Sio2, are called ultrabasic or ultramafic. ”Ultrabasic” magmas are also known as foiditic magmas, such as nephelinites, melililitites and leucites. ”Ultramafic” are rich in magnesium and iron, like prehistoric komatiites. Ultramafic rocks can have 50% silica and are rich in magnesium. Nyiragongo on the other hand is is ”ultrabasic”, very low in silica and is quite low in magnesium and iron as well. In short, to make it clear for the Volcanocafe readers, ultramafic and ultrabasic magmas are not the same thing. A real ultramafic magma has a very high magnesium content, and the silica content is not important for that classification. A real ultrabasic magma for classification has a very low silica content, below 42%.

Most other low silica volcanoes on Earth have magmas with silicate contents in the range of 46% to 50%. But Nyiragongo produces very silicate-undersaturated magmas with silicate contents as low as 36%. Nyiragongo’s magmas are in a group called ”foidites”, rich in sodium and alkaline minerals. Nyiragongo’s magmas are much more silica undersaturated and richer in nepheline than ordinary alkaline basalts and that is the difference from more normal mildly alkali basalts. Nyiragongo’s magma series are uncommon on Earths surface. Nyiragongo is at current the only major active wholly nephelinitic volcano. Nyiragongo’s magma is mostly made of nepheline, leucite and clinopyroxene minerals.

Nephelinite magmas are the peak of silica undersaturation and enrichment of alkaline minerals. This magma is placed in the far left upper section of geochemical TAS diagram. Nyiragongo’s magmas are full of Na2O + K2O rich minerals. The cloudy grey mineral nepheline is what gives Nyiragongo’s magmas the word ”nephelinite” and it is heavily involved in this magma composition. Nyiragongo’s magmas are the product of very small amounts of melting. Perhaps less than 3% of the whole mantle material composition has to melt to form a nephelinite magma, that is why they are so uncommon magmas. Perhaps much less than one thousand of a % of Earth’s surface extrusive rocks are foiditic. like Nyiragongos nephelinites rocks produced by very small amounts of melting in the mantle.

Ultra alkaline volcanism like Nyiragongo is mostly found in slow spreading continental rifts or in weak oceanic hotspots, where partial melting is small. Most nephelinitic volcanism is limited to monogenetic fields because of the small melt rates in the mantle, so Nyiragongo is unusually large and productive for being a nephelinite volcano. It is unknown why that is, perhaps feeding from a large area of small amounts of partial melting.

Nyiramuragira and Nyiragongo are noteworthy for their volcanic productivity despite their alkalinity. The reason the Virunga area is able to produce these large amounts of nephelinites and basanites is because the mantle under Virunga is probably melting far too deep to produce ”normal basalt lavas”. Instead we get large amounts of alkalines if you have melting very deep under high pressure. Nyiragongo is notably more alkaline and SiO2 undersaturated than her sister, so Nyiragongo has the deepest melting source among Virunga’s central volcanoes, perhaps well below 100 kilometers, making nephelinites together with melilitites one of the very deepest magmas sourced from partial melting. Nyiragongo’s nephelinites are low in SiO2 but they are as rock groundmass perhaps not as dark as highly mafic basalts.

Nephelinite is the extrusive form of ijolite magma while ijolite is the coarse grained plutonic version of a nephelinite. Both of these contains around 36% to 38% silica and have identical composition. Ijolite is an ultrabasic alkaline plutonic rock. Nyiragongo’s magma chamber complex is probably encased in ijolite complexes. This rock is a window into Nyiragongo’s depths. Ijolite is a rare plutonic rock only found in a few outcrops in the world such as the Alnö complex in Sweden. These rocks are the ”Roots of Nyiragongo”. Ijolites usually occur as small plugs within zoned alkalic intrusive complexes, or as dikes sills they are almost exclusively associated with (extinct) continental rift-related tectonic settings. They can also be found in Canary Islands.

Nyiragongo haves only 36% SiO2 so its easy for a person who is new to geology to believe it is an ultramafic lava.. But Nyiragongo is also quite low in iron and magnesium, and it is an ultrabasic rock, not ultramafic. Ultrabasic magmas haves very low silica but are also low in magnesium and iron. As an example komatiites are true ultramafic rocks which have much higher silica contents of 50% than Nyiragongo’s super-alkaline nephelinite. Nephelinites and melilitites can also have magnesium content in the ultramafic range, since their high alkalinity increases other elements at the expense of removal of SiO2 in the melt. Other true ultrabasic magmas are ultra low silica melilitites that are even more alkaline and silica undersaturated than a nephelinite. A slightly more SiO2 rich ultrabasic magma is basanite that is slightly higher in silicon and less rich in nepheline than a nephelinite is. Nyiragongo’s magmas are mostly made of alkaline foid minerals, formed by the smallest amounts of partial melting in the mantle. Many other nephelinites seem to emerge as quite cool and crystalline melts because of their low temperatures as a product of small amounts of partial melting. Lengai is mostly made of the same Nyiragongo rocks but estimated to have been erupted as crystalline mush at 900 C. Today Lengai produces carbonatites. Little is known about how other nephelinite eruptions behave outside Nyiragongo, but because they are product of such little partial melting many of them probably erupt as cool viscous Strombolian flows, but hot highly fluid examples too exist if they rise quickly from the mantle as they should do with their extreme CO2 content. Many nephelinite rocks haves large leucite crystal porphyry that can be seen in some of Nyiragongo specimens, but Nyiragongo rocks from recent times are mostly fine grained with crystals only visible with microscopes. Nephelinites are extremely gas rich compared to basalts, and most monogenetic examples are explosion maars, while rare long lived nephelinitic volcanic centers build up steep tephra stratocones, formed by paroxymal fountains and plinian eruptions. Nephelinite extrusive rocks are often found as small dykes, monogenetic cones, tuff cones and maars.

Nyiragongo’s lavas are known to have very low viscosity, which means it flows very easily, and that may have to do with Nyiragongo being much higher in temperatures than most other nephelinitic melts. Nyiragongo’s lava lake temperatures are in the range of 1100 degrees C and that combined with the very low silica content makes a very low viscosity magmatic melt. The current silicate content of Nyiragongo is in the range of 36.5 % with some earlier deposits going up in 37.6%. In summary Nyiragongo’s nephelinites are down at 36% silicon dioxide and most other more normal mafic basaltic lavas are 50 to 46% silica. The very low silica content means little polymerisation in Nyiragongo’s highly alkaline silica undersaturated melts.

Nephelinitic volcanism is very rare indeed and occurs in minimal amounts in places with continental rifting or in oceanic islands, or continental field hotspots. They prefer a deep lithosphere and small amounts of melting. The magma composition can be found outside Africa, in places like, the older postshield hawaiian islands that erupt their last dregs after they left the hotspot, in the Canary Islands, in the Eifel volcanic field, Ingakslugwat hills, Northern Cordilleran Volcanic Province and the late stage volcanics of Bermuda that rivals Nyiragongo is low silica.

Nyiragongos nephelinites are are as I described above a ”Foidite” and that is a whole class of extraordinary rare, very alkaline rich, rare silica undersaturated extrusive rocks. Extrusive rocks that can classify as foidites are nephelinite (Na-rich), leucitite (K-rich) and/or melilitite (>10% bearing of the mineral melilite). The lava currently produced by Nyriagongo is the latter. The difference between these foiditic rocks is which mineral dominates in the magma. A nephelinite is a foid that is dominated by nepheline and a leucitite is a foid magma that is dominated by the mineral leucite and so on. These are all very uncommon rocks, and found in very small amounts in the East African Rift and at other locations. The Nyiragongo cone itself is made of nephelinite but its flank cones haves a melilitite lava composition. The central volcano of Nyiragongo erupts slightly more evolved compositions than its flank cones probably because a shallow storage system.

Nyiragongo’s current (historical) magma is a melilitite – nephelinite, meaning it bears some amount of melilite minerals in the composition, but is not dominated by it. Nepheline is the dominant mineral, giving it the name nephelinite. These are not in any way ultramafic magmas as mentioned above, Nyiragongo is very low in silica but not very high in magnesium and iron either. They are ”ultrabasic” as described above. The minerals in Nyiragongo’s magma forms in a silica poor melting process, where there is not enough silica in the magmatic solution to form normal feldspar and quartz. The magmas of Nyiragongo represent the peak of silica undersaturation and enrichment in alkaline metals and alkaline minerals. The magma chemistry in other words have a lot of their silica bindings with sodium in the mineralogy.

Nyiragongo’s main cone is made of nephelinite lavas and tephras, but its monogenetic flank cones are made of even more silica poor melilitites lavas, that are even more silica undersaturated, so that could indicate that Nyiragongo’s nephelinites are an evolved melt sourced from rising melilititic magmas from deep below.

Video/ photo by Martin Rietze http://www.mrietze.com/images/kongo07/ani-a512.gif

http://www.mrietze.com/kongo07.htm The 2003 – 2021 summit lava lake degassing along the lakes edge Nyiragongos nephelinite is one of the most fluid silicate magmas in the world, and the world’s most gas-rich lava lake, this lake was destroyed in 2021 drain-out: more videos and photos via the links.

The most silica poor foidities

I have shown here that Nyiragongo is already an extreme composition, but because Nyiragongo is a well formed magma system, its nephelinites can allow to cool and evolve a little, meaning they are not fully fresh. The most silica-poor nephelinites and melilities have been erupted by monogenetic volcanism and deep eruptions without shallow storage. Older volcanoes like the old German volcanoes Vogelsberg, Urach have erupted lavas with SiO2 well below 30% with some from the Urach complex getting down to almost 20% SiO2. They are the most extremely silica undersaturated magmas on this planet, and sit well below Nyiragongo’s 36% SiO2. All of these magmas are a rarity. Even more silica poor is kimberlite, but it is not closely related to Nyiragongo’s nephelinites. Kimberlites are much more MgO rich than Nyiragongo is. The compositions of the Vogelsberg and Urach nephelinites and melilitites were provided by Hector in his own article links. It surprised me a lot and was very extraordinary that SiO2 based magmas can go that low in SiO2 content. Nyiragongo has a very low SiO2, but magmas like this can be even more silica undersaturated than Nyiragongo’s recent historical compositions. Nyiragongo is perhaps that SiO2 poor 100 kilometers down where it receives its magma from partial melting. The magma mix evolves a bit as it rises up, We can only speculate, but Nyiragongos really deep magmas are probably meliliteits as discussed above.

Photo year 2011 by Thorsten Böckel showing the very low viscosity of Nyiragongos 2003 -2021 lava lake. Nyiragongo’s lava lakes have small bubbles and small crustal plates, which probably has to do with the very low viscosity or fast circulation, or it being more gas rich than normal basaltic lakes. More photos here link: http://www.tboeckel.de/

A CO2 rich…relationship

Magmas that are as very alkaline as Nyiragongo is are extraordinary rich in carbon dioxide, Nyiragongo and Nyiramuragira are among the largest CO2 gas producers among individual volcanoes on this planet. The CO2 production is quite notable for the locals, with hazardous gas pockets in low lying areas that can kill animals and small children. These pockets are called Mazukus or ”evil winds” in the local folk lore, and they are found everywhere around these volcanoes. Lake Kivu have been force-fed CO2 from Nyiragongo and its sister through submarine geothermal springs and now over 400 km3 of CO2 laden water exist in a volatile layer along the lake bottom, in a stable condition as long as nothing disturbs it. Alkaline magmas like that are less polymerized and the chemical makeup of the SiO2 bonds in Nephelinite allows CO2 to more easily to be dissolved into the magma. The magma can take up more CO2 gas then what a normal basaltic magma would do. The very low viscosity of this magma allows the gases to escape very easily when the magma rises towards the surface and decompresses, explaining the very high gas emissions of Nyiragongo. Magmas like Nyiragongo’s can have a CO2 content that is many 10 s to even 100 s of times higher than a normal basalt, and it explains why many ultra alkaline magmas forms explosive maars rather than lava flows despite their low silica content. The Lengai nephelinites that co–exist with its carbonatites have 300 times the CO2 amount compared to a normal mid ocean ridge basalt. In other words Nyiragongo and Lengai are probably the world’s most gas rich open vent volcanoes.

Nephelinite magmas are CO2 rich and seems to have a relationship with carbonatites as nephelinite volcanism and carbonatite volcanism almost always occurs together. That relationship can clearly be seen in the Alnö Igenous Complex, where the plutonic versions of these two extrusives can be seen together in the same outcrops, with carbonatite dykes seen in ijolite. The volcano Lengai in Tanzania is composed of a mix of nephelinite, phonolite and carbonatitic materials. Geologists today think that carbonatite is formed deep down from CO2 rich silicate magmas like nephelinites. Deep down under high pressure, the CO2 gas increases and accumulate until it reach saturation and the CO2 separate into a hot liquid, being of different density the carbonatite and nephelinite cannot mix and the magmatic system can erupt carbonatites. While carbonatite has a relationship with nephelinites, carbonatites have never been seen erupting out of Nyiragongo. The detailed genesis and mineralogy of Carbonatites are so complicated that we will not go further into that in this article series.

The plutonic version of a nephelinite magmas is called a Ijolite, same composition just coarse grained and intrusive. Ijolite is a very uncommon rock, formed by minute amounts of partial melting, and the extrusive form is even rarer on Earth’s surface. These types groups of igneous rocks makes up much less than 1% of Earths surface rocks. Its mostly made of nepheline and pyroxene minerals, the white is nepheline. Another related uncommon superalkaline plutonic rock is called urtite. Ijolites are often found together with carbonatite proving their CO2 rich relationship.

A look at some of the minerals present in Nyiragongo’s magma

Most of Nyiragongo’s nephelinite rocks are composed of nepheline, a cloudy dull grey whitish mineral. nepheline is a bit of a puzzle in many alkaline magmas. Its a silica-undersaturated aluminosilicate, Na3KAl4Si4O16. Nepheline is the major component of Nyiragongo magmas. This mineral is used in glass and ceramic manufacturing and other industries. Nepheline is the dominant feldspathoid mineral in Nyiragongo’s lavas

Another mineral that can be present in a nephelinite is leucite, another highly silica undersaturated alkaline mineral with chemical formula KAlSi2O6. It is silica-undersaturated and is composed of potassium and aluminium. Vesuvius has good examples of large leucite crystals in some of its lava flows.

Another mineral that can be present in Nyiragongo’s magmas is Melilite. The formula for common melilite is (Ca,Na)2(Al,Mg,Fe2+)[(Al,Si)SiO7]. Discovered in 1793 near Rome, it has a yellowish, greenish-brown color. The name derives from the Greek words meli (μέλι) “honey” and lithos (λίθους) “stone”. It occurs in very silica undersatuared rocks and is not a common igneous mineral.

Earlier Nyiragongo eruptions and deposits erupted melilite – leucite/olivine – melilitites lavas which is another extraordinary rare silica undersaturated alkaline rock.

Another mineral is Augite that belongs to the pyroxene family. It has the chemical composition (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6. These crystals are white or ash-grey in colour, hence the name suggested by A. G. Werner in 1701, from λευκος, ‘(matt) white’. They are transparent, a little milky and glassy when fresh, albeit with a noticeably subdued ‘subvitreous’ lustre due to the low refractive index,

Nyiragongo is a very Feldspathoid mineral rich composition. These minerals are also known as foid minerals, they resemble feldspars but have a different structure and much lower silica content. They occur in these rare and unusual types of alkaline igneous rocks, and are not found in normal more silica rich subalkaline magmas. Igneous rocks rich in nepheline, leucite, melililite and devoid of silica rich minerals are called as mentioned above ”foids”.

Nyiragongo’s magma has the dominant mineral atoms, silica, sodium, aluminium and oxygen, while a normal Icelandic thoelite basalt from high melting rates haves the atoms iron, magnesium, silica, oxygen, calcium. This shows how different Nyiragongo’s ultra-alkaline magmas are compared to normal subalkaline magmas such as Icelandic and Hawaiian basalts.

The conclusion of looking at Nyiragongos magma composition is that it is a magma that is not very common, and maybe the rarest type of extrusive rock togther with melilitites and kimberlites. It is this ultrabasic compostion that makes this volcano so famous in the petrological world, and it has the record for lowest SiO2 among currently erupting silicate magmas. There are even more extraordinary SiO2 saturation among this nephelinite magma group than in Nyiragongo and the more undersaturation the rarer they get as extrusives.

Photo: by the famous Maurice and Katia Krafft from their 1982 visit of Nyiragongo. It shows the low viscosity of Nyiragongo’s lava, that is very much lower in sillica than a normal basaltic lava, but plume basalt lavas in Iceland and Hawaii can very likely have same viscosity because of their high temperatures. Nyiragongo’s lava contains a lot more carbon dioxide gas than ordinary subalkaline basalts. Link http://jdelort.free.fr/krafft/QR.php

Photo by Jack P Lockwood, showing the high fluidity of Nyiragongo’s magma composition from one of the 2002 flows: link:  https://disastervru.files.wordpress.com/2018/09/john_lockwood_richard_w-_hazlett_volcanoes_glob-ok-xyz.pdf

Now I have explained Nyiragongo’s magma composition and explained how unusual that is compared to most other magma chemistries. In the last part, I will have a look at the behaviour of this lava and we will discuss if it really is more fluid than other low viscosity silicate magmas.

Jesper, July 2022

238 thoughts on “Nyiragongo and its ultra alkaline magma – Part III

    • Indeed quite an unusual lava for soure
      I wonder if Nephelinite soil is more fertile than normal basaltic soil

  1. Good question. Only volcano I know that is said to be exceptionally fertile compared to volcanic soils in general is Lengai.

    Depends perhaps on if all ultra-alkaline magmas are richer in nutrients? Other than phosphorus and nitrates I’m not too familiar in what else plants thrive in.

    • Plants really like potassium too, so ultrapotassic basalts and similar might be the best soil. I know Vesuvius is particularly notable, which is in part why people are still living on it despite the risk that is known, they are taking the same gamble as those in Hawaii down in Puna, the risk of an eruption is there but if it is infrequent enough then the interval is worth it. Vesuvius is probably going to be asleep for a long time though, several centuries if the intervals before 1631 and 79 AD are an indication, and the resulting eruption will be a VEI 4-5 and quite a disaster if the city planning isnt changed…

      I wonder if maybe Nyiragongo is a lot like Vesuvius and we have just got a snapshot of it with an open system. Recorded history for Virunga is only really about 150 years, if you took 150 years of time at Vesuvius before 1944 and only had that to go by you would draw the conclusion it was also a passive open lava lake volcano that was only dangerous if a flank vent opened without warning, but because we have got over 2000 years of good records, we know the reality of the situation. Nyiragongo is actually even more gas rich than Vesuvius, so in theory its eruptions should be more violent all other things equal.

      • And most of Nyiragongos caldera interior is made of Brown tephra so probaly been explosive for most of its existence with eruptions like Villaricca 2015 .. but perhaps even more powerful than that

      • Aside from probably being more productive isn’t the chemical composition a bit different too?

        From what I recall doesn’t Vesuvius erupt basanite -> phonolite which suggests lower alkali but higher silica content.

        • Yes composition isnt the same, more that in terms of physical properties the two volcanoes seem to be very similar, but one has a 2000+ year observational history and the other is only really about 150 years, and really only since the 1950s.

        • Higher silica content also is sort of relative in this context, phonolite is only about the same silica content as basaltic andesite just with extreme alkali content it actually does evolve further, by crystalizing alkali component so that it decreases in alkalinity to become rhyolite.

          Basantite is borderline ultramafic, it is probably not too inaccurate to call it ‘alkali komatiite” as it has under 45% SiO2 but low Mg compared to Na+K. It is just that nephelinite has even more alkali and less SiO2, under 37% and with 15% alkali in the case of Nyiragongo.

          Basantite is what was erupted on La Palma last year. It is erupted usually at a high temperature and might be the most fluid of all magmas today. Hot primitive magma of any type is going to be very fluid but the numbers from La Palma are extraordinary, as are the visuals for when this happened. Some calculations are for a temperature over 1200 C and viscosity that is only a couple of times higher than water, two orders of magnitude less than the lava lake at Kilauea…

          • There are a few things that make Vesuvius more dangerous. First and probably most important, Vesuvius is a caldera system, Nyiragongo is not, at least not yet. The most violent eruptions of Vesuvius have had a component of caldera collapse, like 79 AD or 1631 eruptions. These eruptions certainly involved large volumes of magma being rapidly released from a magma chamber, and possibly with the help of a ring dike. In fact Vesuvius and Colli Albani are probably the only two active caldera systems in the world that erupt foiditic magmas. Also, the most violent eruptions of Vesuvius have involved phonolites in their initial phases which are somewhat more viscous than basalts, and this favours higher eruption rates due to wider conduits needed to channelize more viscous magmas.

            This is Ol Doinyo Lengai erupting nephelinite similar to Nyiragongo’s:

            From Global Volcanism program.

            They do remind somewhat to the tephriphonolitic eruptions of Vesuvius which also were driven by very fluid magma:

            However without a ring dike eruption rates of such magmas are probably not enough to drive major plinian eruptions like those produced by silicic magmas with normal pipe conduis.

          • I must say the term alkali is misleading though. They do generally have higher alkali metal concentrations, Na and K, but this is far from being their most defining characteristic, and is not always true anyway. Melilitites have actually less sodium than basalt, and kimberlites basically have no sodium. Igwisi Hills Kimberlite has 0.1 wt% Na, Katunga melilitite has 1.3 wt% Na, while Erta Ale basalt has 2.8 wt% Na. And while they do are always very potassium rich, the enrichment in other elements like F, Cl, C, Ba, Rb, Th or U is greater than the enrichment in K. In particular the enrichment of carbon and fluorine is extreme, much more than the others. The terms potassic or silica-undersaturated might be more spot on.

          • Actually those historical Vesuvius subplinian eruptions are phonotephrite I think, not tephriphonolite, that was a mistake, and the painting is from the 1794 eruption.

            And also basanites do are richer in sodium than basalts, but melilitites and kimberlites get gradually more depleted in sodium, at the same time as they get depleted in silicon and aluminium.

          • Actually now that I’m looking at it Igwisi Hills doesn’t have any potassium either. 0.1 wt% sodium, 0.05 wt% potassium. I hadn’t something like this ever before. It is almost as if it had lost all the sodium and potassium. The only exlanation I can think of is that the kimberlite of Igwisi Hills might have been the silicate remnant of a partition between silicate and carbonatite, and that the carbonatite took all the sodium and potassium with it. Ol Donyo Lengai carbonatites are mostly carbon, sodium, calcium, potassium and fluorine oxides. So certainly it would make sense in the sodium and potassium part that the Igwisi Hills had lost it all to a carbonatite.

          • It is amazing really how much carbon there must have been in the original magma of the Igiwisi Hills. The erupted kimberlites still contain an average of 14 wt% dissolved CO2. The magma must have lost a great deal of carbon to the carbonatite melt, then it must have degassed more carbon while erupting, and yet the degassed lavas still retain 14 wt% CO2. Considering that Mid Ocean Ridge basalt, the dominant magma on Earth, contains only 0.046 wt% CO2 in its undegassed crystal inclusions, the difference is quite significant.

          • I forgot that I was quoting oxide concentrations in a lot of places, a lot of missing O…

          • I thought the most violent eruption ever made by Vesuvius was the Avellino eruption around 1500-2000 BCE, which was considered a VEI 6. Also, somewhat odd that I add this next to that context, but could Vesuvius turn into something like Campi Flegeri in the next few thousands of years?

          • I wonder if the enrichment in F and Cl compared to other magmas has an impact on viscosity. Fluorite (CaF2) is used in steel production to lower the viscosity of the slag, which for all practical comparisons is basically an artificial magma. I did propose this once as an idea why Hekla can erupt lava that looks like sticky basalt but is actually andesite, I think that is very unlikely now (Hekla is only F enriched relative to other Icelandic volcanoes that have basically none) but it might be a lot more viable in these ultrabasic magmas.

            Actually I dont know what sort of lava slag would be, on the Na K vs SiO2 graph it is in the foidite range but that completely ignores that the slag is almost 50% CaO by weight and the largest single ingredient, I dont think calcium dominated magmas exist naturally.

          • Campi Flegri is a mostly silicic caldera, erupting mostly trachyte and basalt, so it is probably a good bit less alkaline than Vesuvius as well as being evolved. Vesuvius probably does have a large magma chamber in the right place but given most eruptions have been fluid lava flows it is unlikely any part of the system really has a chance to evolve except for maybe the upper part of the conduit.

            Maybe one day it will become like its neighbor, but Campi Flegri seems to have become a massive caldera quickly, its earliest confirmed eruptions were 45000 years ago and the VEI 7 Campanian ignimbrite was only 11000 years later. Vesuvius as we know it now began forming 25,000 years ago with many caldera formation between 19,000 years ago up to possibly 79 AD. So it did produce calderas about as quickly as Campi Flegrei but of much lower magnitude in comparison. Probably since 79 AD it has gone back to a second phase of stratovolcano construction, it might well be millennia before another eruption as big as what is considered the worst case happens, although not a good idea to build on it still…

          • Now that I think of it, aren’t a lot of the mainland Italian volcanoes on higher on the alkali side of the chart than typical for a subduction setting? I seem to remember trachytes all the way from Amiata in the north all the way down to the current activity in Campania.

            Is Italian subduction younger than for example the Ring of Fire? Could that be the explanation?

          • Yes, most Italian volcanoes are alkaline. Including all the mainland volcanoes, as well as Etna and Pantelleria. The ones that are related to the subduction zone however are mainly subalkaline. The Aeolian Islands are subalkaline/low potassium, except Vulcano and Stromboli which are mildly alkaline. Marsili is also subalkaline/low potassium.

            It’s really hard to make sense of the pattern of alkalinity. You could think that continental volcanoes are more potassic. Then again Vesuvius is a lot more potassic than Campi Flegrei, and they are right next to each other. While Vulcano is significantly more potassic than Lipari and they are also stuck together. You have Ciomadul, a weak volcano in Romania, right in the midst of the European continent, which happens to be low potassium and then Stromboli a very active oceanic volcano which is more potassic than Ciomadul.

          • Hector,

            I know this may seem somewhat obvious (but I’m still trying to fully wrap my mind around these dynamics), but what are the reasons two different volcanoes erupting magma of the same chemistry may differ so much in their eruptive processes? IE Nyiragongo erupting Nepheline effusively and Lengai explosively?

            Is it the mechanics of the conduit, or what other factors can modulate this?

            Thanks.

          • It’s a actually a very complicated matter that has taken me a long time to understand. My understanding comes partly from the Pu’u’o’o and Mauna Ulu eruptions. These two eruption switched from a high fountaining/explosive mode to a lava lake/effusive mode. In the case of Mauna Ulu it is well documented how the conduit gradually widened, at least its top section. So I think it has to do with conduit width.

            Explosive eruptions are driven by the growth of gas bubbles in the magma. Gas bubbles can increase the volume of the magma in the conduit by a factor of 100 or more, at least in reticulites. So if gas bubbles start growing rapidly, the magma basically explodes because it cannot be contained in the conduit. But for gas bubbles to grow you need some upward motion of the magma which causes it to decompress (or the more brute way of relieving weight from the magma, eg. Saint Helens). This process I think is very well seen in Etna where the paroxysms pick up strenght gradually. Deep magma influx causes magma to rise to the surface. First you see a lava flow and some weak strombolian explosions. Volatiles start to nucleate. Explosions pick up frequency. The magma keeps accelerating in the conduit and nucleating faster. The frequency of explosions increases until there is no longer any interruption between them and a continuous jet of lava is shooting from the volcano, going ever higher. At some point the flow collapses and eruption suddenly stops. Ol Doinyo Lengai would be like this.

            Nyiragongo however has a very wide conduit. It has a lava lake. Lava can be seen to be continuously upwelling in the lake, but also downwelling. Small lava lakes do something called gas piston events. In gas piston events the lava level of the lake gradually rises by nucleating gas bubbles while there is no spattering. However it reaches a moment where spattering starts somewhere in the lake, the lava is rapidly pulled towards the spattering and sinks, while a lot of gas is released and the lava lake drops. Basically the spattering inhibits explosivity. The spattering does two things, it releases gas bubbles, and creates a localized downwelling of dense degassed lava. So in a lava lake it is very difficult to get an explosive eruption, spattering always shows up and reverses the motion in the conduit to downward by reducing the gas volume. Large lava lakes have no gas pistoning, probably because spattering never stops.

            In other words it is obviously much more difficult to get a 100 meter wide lava lake pipe to rapidly rise and explode than it is to do so with a 5 meter lava pipe. The lava lake circulates and releases the gas. In fact, a lava lake can probably deplete a magma chamber of much of its gas. The first thing that happened before the circulating lava lake of Kilauea showed up in 2008, or the lava lake of Nyamuragira started to grow towards the surface in 2012 was that there were huge gas emissions, way before lava was seen. A large, towering steam column, then a collapsing pit, and finally it fills with a lava lake. Even before the lava lake conduit touches the surface it is already depleting the magma chamber of its volatile content.

            Ring dikes might be similar. I used to think that some lithic eruptions (eruptions that blow the ground to ash but do not emmit any fresh lava) like those of Kilauea in 1790 and Fernandina in 1968, had been driven by water. More recently I have come to think that, at least Kilauea’s case in 1790, was driven by gas coming out of a ring dike so fast that it blew through the bedrock and this explosion sent pyroclastic surges 12 km downslope. Ring dikes however do evolve into proper explosive eruptions, particularly in gas rich magmas, maybe because the collapsing roof of the magma chamber creates a mechanical forcing that rapidly lifts the magma in the ring dike.

          • At Kilauea in 1790 the ring dike did erupt too, or at least it erupted in the next few years. If the collapse in 1790 was of similar speed and intensity to 2018, but was 4-5x the volume, that is over a year. It could have been faster but the 2018 collapse was already pretty extreme as far as eruption rates go and the whole south flank was shoved out of the way to allow the etuption to happen.

            Still, one can imagine that the ring dike blew out as you hypothesize, and then following that every time there was a collapse of the floor the ring dike erupted, it might have sat there in the interval like a glowing line of vents, which fountained violently. The caldera probably had lava in it the whole time from these eruptions but the collapse removed that eventually. It is possible that Halemaumau, or at least the vent that would turn into it, was a part of this ring dike that stayed open after the collapse, as the filling must have been pretty quick to resume if the lake was high enough to induce flank eruptions in the early 19th century.

            I think Strokkur geyser might be a very good isual for how magma conduits look, Fagradalshraun did look remarkably similar to it at times, which is appropriate I think 🙂

          • I think that the high fountaining events of the Golden and Eastern Pumices may have been highly gas driven eruptions with some similarities to the Footprints Ash climactic blast but with a more sustained eruption, and magma closer to the surface. They may be comparable to the gas jetting events of Pu’u’o’o:

            “During the final hours of episodes 42–47, we witnessed a
            new type of fountaining behavior, in which 1–4 brief jetting events
            occurred within the last 2 hours of the episode. A similar event
            near the end of episode 38 was recorded only by time-lapse film.
            Each event lasted 1–2 minutes and consisted of several pulses
            of magma-poor, gas-rich fountains that reached heights as great
            as 550 m (table 3) and created enormous, black tephra columns
            (fig. 18). Jetting fountains were accompanied by a loud hissing
            noise and followed by a brief period when the gas-and-tephra
            plume was so dense that it obscured the incandescent part of the
            fountain. After each event, the fountain died for a few minutes and
            then slowly recovered to its former (pre-jetting) height as a broad,
            smooth-looking fountain (fig. 19).”

            https://pubs.usgs.gov/sir/2018/5109/sir20185109.pdf

            The gas jetting events seem to have happened just as the upward flow in the conduit was collapsing. When the upward flow stalled or maybe even as it reversed, sinking downwards. Gas shot violently from the conduit producing those jetting events and entraining some tephra in them. This may also be related to the 2018 and 1924 explosions of Kilauea, in those cases the lava lake conduit was sinking but magmatic gasses coming from the magma would episodically blast through the overlying rock generating lithic eruptions.

            I highly doubt the ring dike did really erupt properly in 1790, if it did there would have been dense material being ejected, bombs, spatter, pyroclastic flows. The Golden and Eastern Pumices instead produced only very porous pumice and reticulite. They also happened in between lithic eruptions. They followed the climactic explosions of the Footprints Ash and those that followed, and preceded the lithic eruptions of Unit L. I don’t think magma was rising up in the ring dike, simply gas was shooting out from a magma foam that was collapsing in the intrusion. The ring dike would have lacked pressure.

            The eruption of Tarawera in 1886 may have involved similar processes, I’m starting to think. The dike I don’t think reached the surface, so that is why no lava flows were formed. Instead there would have been gas jetting along Mount Tarawera, where the dike came closest to the surface. As the dike propagated, it lost pressure and deepened into the ground. The gas from the dike would have blasted through the rock producing lithic eruptions across Rotomahana and Waimangu.

            Melilitite has really opened my eyes into has magmatic gasses can do on their own.

          • Interesting, although I would consider this still to be a proper eruption even if lava flows didnt form, there is some new material in these lithic eruptions still and the reticulite is entirely new just low density.

            Tarawera was a bit if both, the eruption was a VEI 5, and the size of the craters on the mountain isnt big enough to exain without a lot of magma erupting, the gas content there is high for tholeiite basalt. I do recall there being found some places on Tarawera itself that probably did erupt passively but only very briefly so lava flows were buried by tephra or couldnt form properly. There us also at least one of the Waimangu craters that did erupt some basalt during the eruption too based on isopatch data.

          • If anyone is interested, I was comparing the composition of glass inclusions in basanites and tholeiites from Lanzarote for a number of elements in the magmas. I arrived at these ratios obtained through dividing the concentration of the elements in basanites by their concentration on tholeiites. Unfortunately there was only volatile data for the basanites. It shows how alkaline/potassic magmas are enriched in almost every element. The exceptions in this case are the most abundant elements in magma, silicon and aluminium, as well as the rare earth lutetium. The most enriched seems to be uranium. In Katunga melilitites I seem to remember however that the non-volatile element with the greatest enrichment was barium.

            SIO2 0.898481419
            LU 0.909205331
            AL2O3 0.951272224
            YB 1.032011468
            FEOT 1.047298915
            ER 1.085907382
            MGO 1.100674858
            TM 1.116269143
            TIO2 1.132812558
            NA2O 1.134185705
            HO 1.153974217
            HF 1.164004001
            Y 1.182584239
            TB 1.190636723
            DY 1.210527601
            CAO 1.211874875
            MNO 1.316535082
            CS 1.332147032
            GD 1.355244627
            ZR 1.368243975
            EU 1.572432555
            SM 1.62066688
            K2O 1.746021994
            RB 1.747459333
            TA 1.85698435
            NB 1.992055061
            PB 2.154173182
            SR 2.187206178
            ND 2.226715233
            BA 2.278514283
            P2O5 2.339765685
            PR 2.482065262
            CE 2.805794053
            TH 2.825248675
            LA 2.97444166
            U 2.995002384

          • Regarding Tarawera I should say that morphologically the northeastern craters that issued most of the fresh lava resemble maars somewhat, and are also identical to the ones in Waimangu that erupted only lithics.

            In particular the craters are excavated into the old domes of the Kaharoa eruption. They remind me somewhat of the Hoyo Negro volcano in La Palma which erupted in 1949. Hoyo Negro erupted basanite explosively while simultaneously a lower elevation vent, 2-3 kilometres away, Llano del Banco, issued lava in an entirely effusive way. Hoyo Negro did not make any lava flows at all and erupted in a maar-like activity with pyroclastic surges, and ejection of lithics. There seems to have been a partition between the gas and melt phases, the gas going up through Hoyo Negro and the melt issuing from Llano del Banco.

            There may have been a similar partition in the Tarawera dike with much of the gas rising up, but most of the melt staying within the intrusion, probably the proportion of gas to magma in the northeastern vents of Tarawera would have been much higher that normal for other water-rich basalts, and boosted a very violent explosive style. I wonder if the reason why the dike degassed so violently could have been a greater intrusion width than typical for dikes.

          • Could be, the Waimangu area is still very hot today, even had a geyser that was 500 meters tall of the same name in 1904. 140 years seems very long for a dike to still hold so much heat and the rhyolite would be needing a large supply of hot basalt to keep it molten.

        • I forgot that Elba and Capraia are also low potassium/subalkaline. Those 2 islands offshore Toscana (northern Italy) are located in continental crust, their volcanoes are ancient though, 8-5 million years old.

    • Yes, that is a good question. One of the things that characterize alkaline/potassic/silica-undersaturated magmas is that they have significantly less silicon and less aluminium. Silicon and aluminium happen to be the two most abundant elements in basalt, so reducing their concentration means increasing the concentration of all the weirder stuff. That means they have higher concentrations of most elements. And nephelinites because they are evolved from melilitites they have even more weird stuff, they loose magnesium while evolving, which in turns increases the concentration in phosphorus, potassium and others. For example Nyiragongo nephelinite has 1.45 wt% phosphorus, as opposed to 0.9 wt% phosphorus in Katunga melilitites and 0.3 wt% phosphorus in Erta Ale basalts. Nyiragongo nephelinite has 5.5 wt% K (potassium), Katunga melilitites have 3.8 wt% K, and Erta Ale basalt has 0.56 wt% K. Melilitites are also much richer in magnesium, nickel, and calcium than basalts, and this also holds true for nephelinites as long as they are not too evolved. Problem is that alkaline magmas can get to extreme levels of fluorine, about 100 times more than normal mantle, which might lead to poisoning. So yes, ultrapotassic lavas should be very fertile, however there is a potential fluorine problem.

  2. Part 4 is comming up later and that Will be the last part.

    Dragons in the alkaline section

    Change … Although alkaline elements are common on the Earth’s surface, most magmas are not very rich in these elements.

    Change to

    Although mineral compounds that haves alkaline elements in it are quite common on the Earth’s surface, but most magmas are not very rich in these elements.

    For better science accuracy

    • Hi Jesper – article is good but I think if you have time in future you can probably cut it to say the same thing in fewer words – I couldn’t create this content, so no complaints but I think you said that the magma was ultra basic and not ultra mafic a few times (not a bad thing to drum into our heads, so maybe intentionally done) – also I don’t think you spelled out that Ma is magnesium and Fe is iron.

      • Thanks yes I let Albert edit that. Also I have not had time to write much these days, Part 4 must probaly be Re – written

  3. Just because I was curious, soda lime glass on the alkali/silica graph is properly considered a sort of artificial rhyolite.

    It has got a much more simple composition though, basically only SiO2, Na2O and a few percent each of CaO, MgO and Al2O3. It doesnt have any potassium in the original composition, I dont know if that really matters but it is there still. But assuming 73% SiO2 and 7% Na2O, that would count as a rhyolite.

    • Yes and At most ryholitic temperatures 700 C to perhaps 800 C .. Soda Lime glass is quite stiff .. althrough formable

      But at over 1000 C Soda Lime Glass loose its viscosity quickly and most normal glass furnaces are heated to around 1300 C or up to even 1450 C and at that temperatures Soda Lime flows very easly and can be casted.. and at lower temperatures 900 C it can be molded and blown

      Soda Lime really dont have a melting point at all .. just gets more fluid with increasing temperatures and can be worked with at many difftent temperatures .. a really excellent material is glass .. super-material really so versatile

      You can ”melt” it in a normal camp fire at 800 C as I done many times.

      Nyiragongos low Sio2 is what prevents it from becomming a strange soda glass I guess but Soda glass also have the quartz lime to give it that glassy behaviour

    • Soda Lime have quite alot lower viscosity than a real Ryholite.. the soda lime is what removes the polymerisation

      • Peralkaline rhyolite apparently forms flows of similr scale to basalts, and is erupted much hotter than most other felsic magmas (same range as basalt). That is very similar to glass really except it is naturally occurring.

        Obsidian flows also seem to not be nearly so viscous, being basically completely melt with no crystals. Still nothing like basalt but the lava still manages to flow a long way from the vents in some cases, which is more than can be said of most lava domes.

      • Any Peralkaline Ryholite pahoehoe ? If I Remeber right that New Zeeland haves one

        Yes Obsidian can flow kilometers long .. Probaly because it emerges at close to a 1000 C and lava have very low heat conductivity, so it keeps flowing as long as vent is alive.. keeping its heat well

        • There are lots of peralkaline rhyolitic volcanoes in Ethiopia, instead of lava domes they form stratovolcanoes with a’a flows that look like basalt but not black. No pahoehoe though but evidently the melt is able to flow.

          Where is the New Zealand example?

          • Tarawera I presume? I mean the lava flows of rhyolite from the fissure vents look like lava flows instead of domes. Yellowstone also has quite volumous lava flows, too, maybe dwarfing that of Laki, although slower.

          • But those are not pahoehoe flows, they resemble the structure on a huge scale but I am talking lava of rhyolite composition that forms flows of similar viscosity to some of the lava flows in Hawaii.

            Tarawera I think might actually be best regarded as a former rhyolite volcano. It was created in the late Pleistocene but stopped, and up until 1315 all Holocene eruptions from Okataina were from the Haroharo fissure swarm, which made alot of large flat rhyolite domes. The 1315 Kaharoa eruption was the first Holocene eruption at Tarawera and erupted old crystaline rhyolite hence the domes being pretty steep and most of the eruption volume being tephra, where eruptions on Haroharo and Pleistocene eruptions erupted much more lava than tephra. There were also a lot of maars created along the axis of the dike intrusion although no basalt erupted that I know of. In 1886 the basalt directly erupted immediately, lots of theories as to how it avoided the rhyolite but I think the easiest is that the rhyolite isnt there anymore, it crystalized and the last of it erupted in 1315, although it will take another eruption to prove that.

          • As for Yellowstone, those flows make Laki look insignificant, and that is not even doing it justice. They are the biggest lava flows on land in the Quaternary period full stop. There is over 1000 km3 of rhyolite flows erupted from the caldera fault between 150,000 and 70,000 years ago and individual eruptions are going on 80-100 km3 of lava, flowing like a glacier made of glass, dwarfing everything else in the landscape and flowing tens of km from the source. Despite being silicic the eruptions were effusive but still erupted very fast, probably at rates of hundreds of m3/s or even thousands, it is a literal mountain forming in a year. Yellowstone is absolutely a monster of a volcano just not the one the media talks about.

          • I think I kinda got that first assumption wrong. There is Mayor Island (or Tūhua) where it us a shield volcano made mostly of rhyolite. I presume this is the one?

    • “By adding soda (sodium carbonate), the melting point of the sand is reduced so it can be transformed into glass at lower temperatures and save energy during manufacturing. However, adding soda to the mixture reduces its chemical durability, making it prone to dissolve when in contact with liquids. For most applications, that’s not desirable, so limestone (calcium carbonate) is also added to the mixture, which acts as a stabilizer. Once the mixture of silica, soda, and limestone is heated, it can be cooled and moulded for a variety of applications. ”
      Basic sods glass seems to analyse out at about 74% SiO2, 13% Na2O, 10% CaO.

    • I saw they pegged the alert level to 5, but information on what’s going on is sparse currently (eruption just started).

      I’ve read recently that Sakurajima may have a large eruption essentially tomorrow or in the next decade or so.

      They have people evacuating which suggests this may feel this will be a pretty decent event. I suppose that shot of a small/moderate vulcanian explosion the other day was the throat clearing episode.

    • Thanks. I saw a snippet on the news, so I immediately checked Volcano Cafe to see if anyone had any comments or insight. Thanks

      Which leads me to suggest a maybe a small change in the site organization. People seem to comment on current events in the comment section of the most recent article. Perhaps the site might have a dedicated thread for current events that haven’t yet resulted in an article? Might serve as a useful chronological archive. But we’d want the most recent comments at the top. Maybe that’s not possible here.

      • It is a frequent eruptor and it seems this one is not out of the normal range. But a larger eruption is possible. In the post ‘Up!’ we wrote about this volcano that a larger eruption can be expected by 2044.

        https://www.volcanocafe.org/up/

  4. Tangential, for Vesuvius, could its contrary make-up be related to the Med’s Messinian event, in that erratic closing of Tethys could provide ample saline ingredients to subduction zone and slab-gap…

    But, if that is case for Vesuvius, how did such makings get swept far under Africa ? IIRC, its cratons are very old, have been stuck together ‘as seen’ for a very long time, even by geo-standards…

    And yet something is feeding Tibesti, too…

      • Seems to have been doing the same sort of slow constant eruption for a while now, since at least 2014 but probably since 2012 when summit SO2 increased and the flank vent suddenly stopped. Might not be as fast as at Kilauea, or what Nyiragongo was doing in the year up to its last eruption, but seems to be very much persistent.

        Might well fill the caldera entirely in a decade or two, but I think it will have a flank eruption before that. Maybe it cant really engage in shield building anymore as there is a shallow magma chamber, so instead of that it does fast eruptions. Seems the same as Kilauea which was able to do shield building in the 1400s but now magma goes off into the rift before that happens. Nyamuragira had a lava lake in the 1930s that drained out in a major eruption.

      • Actually, based on where the hotspots are the southwest pit within the caldera might have been filled up, although the caldera itself has not overflowed. There is a picture on google earth from March this year that shows the flows in the caldera are smooth pahoehoe surface so it is probably acting as a rootless lava lake. There is probably a lava tube from the vent into that part.

        Not sure how trustworthy google earth is, but the lava in that crater (I think the 1938 collapse) is probably about 150 meters deep and is about 1100×750 meters, so it might be similar to the amount of lava Kilauea has erupted since September, about 100 million m3. Overflows began in June 2020, no data on how big the caldera is by volume but the outer rim is abotu 50-60 meters high and 2 km wide, which is a volume of 170 million m3, and it seems both of the pits have filled in so that number is probably more or less pretty good now. At the rate things have been going so far it could overflow in 3-4 years, or in 2025-2026.

        That is about the same time as Kilauea could overflow its caldera… Might be a good bet which will overflow first, or if they will have flank eruptions before that happens 🙂

        • There is also alot of tube feed pahoehoe filling the caldera … use SWIR layer on Nyiramuragira

          The Nyiramuragira pit recollapsed in Early 2021 : ) Althrough not as deeply as before and its been filled up competely now

  5. I’m a bit late to the party, but well done on a cracking third article that is accessible even to a dummy like me! Excellent work, Jesper! Thank you!

    • Thank you! Im still improving it
      Sent things to Albert that I wants to be added in the article

  6. Ok, bit odd, but there’s a swarm of around 23 earthquakes in south central France near the Chaîne des Puys volcanic field.

    They start around 5km beneath the ground and seem to make there way up to the surface.

    • I dont know what this area is usually like, but the way they are densely clustered seems to be concerning. if there is an eruption it wont be big but for sure will leave its mark.

      Approximate location of the quakes.

      • And with obvious vents marked. It is not exactly on the trend but close enough…

          • I only found out when I looked at an earthquakes near volcanos report on Volcano Discovery. There’s about 3 that are mag 2.0 but the majority seem to be smaller.

          • This has been going since March or so, with as strongest event an M4 in May. It is moving around a bit which suggests it is a fault rather than a volcano

          • https://www.volcanodiscovery.com/region/8176/earthquakes/puy-de-dome.html

            The earthquakes are happening under one of the two big central volcanoes of Massif Central, Monts Dore. Although Monts Dore is presumed to be extinct, there are young plesitocene-holocene volcanic vents to the south and north of it. To the north is the Chaine des Puys, and to the south 7000 years old Lac Pavin and other vents. The earthquakes are roughly happening along this line.

            Of course it is unlikely that this is volcanic with the region having been dormant for the past 7000 years. The location is interesting though.

          • Most likely it’s just a mainshock-aftershock sequence. With the M 2.6 setting off a series of aftershocks.

  7. I’m a bit surprised that the M4.9 from Bárðarbunga hasn’t been mentioned yet. It’s on par with the largest post-eruption quake so far.

    Sunday
    24.07.2022 13:45:41 64.668 -17.462 2.6 km 4.9 99.0 4.3 km NE of Bárðarbunga

    One thing that looks odd about this quake is the focal mechanism. All other large quakes on the caldera rim that I’ve seen focal mechanisms for have had a strong vertical-CLVD component. This one looks more like a strike-slip event.

    https://www.emsc-csem.org/Earthquake/tensors.php?id=1152275&year=2022;INFO

  8. 5.2-5.7 just occurred at the one of the faults near Chiles-cerro negro, article in the works.

    • If we get another VEI 5 eruption it’s going to end up being a very memorable year from a volcanic-explosive perspective.

      • I just got wind of this Chiles-cerro negro thing (although I first remember hearing about it several years ago). Does anyone here want to discuss this in more detail ? (it is now July 29 at 2:15 UTC).
        The following list reflects some of my thoughts/questions about this activity:
        -Is this system eruptively inactive ? for perhaps >10^5 years ?
        -What about the last activity before the cessation of stratocone building here, specifically the large lava flows with ogives or concentric pressure ridges on Chiles cone (the larger eastern cone) ?
        -Are the large late lavas on Chiles silicic ? (perhaps crystal poor rhyodacite/rhyolite)? or intermediate ? (perhaps crystal rich andesite/dacite) ?
        -Is the large erosional scarp on the north side of Chiles from gradual erosion, or multiple slides, or a large sector collapse ?
        -Did the scarp occur significantly after the the end of stratocone construction ( i.e. a newer feature) ?
        -About the outcome of the new/ongoing intrusion…..the latest unrest of a long lived intrusive magmatic system responsible for the large and long lived hydrothermal system, perhaps dating back to the end of stratocone growth ? if so, perhaps eruption unlikely ?
        -alternatively is the intrusion is a new feature unrelated to the growth of the old stratocones ? if so, perhaps eruption more likely ?
        Possible eruption scenarios………
        -Possible resumption of stratocone growth after long period of inactivity, leading to the eventual construction of a new stratocone such as Negro or Chiles ?
        -A large explosive silicic eruption with Santa Maria 1902 or Huaynaputina 1600 as possible historic analogs ?
        -An eruptive outcome unlike either of the 2 discussed above ?
        If anybody has any thoughts about this please let me know.

        • I think GVP had the area listed as active but the presence of Holocene eruptions is unconfirmed, and based on appearence looks unlikely. Lava is dacite from more recent flows. Chiles is at least 160,000 years old, Cerro Negro is probably way younger maybe only a few tens of thousand but seems to have stopped too. Both stratovolcanoes are probably extinct so a new eruption might be anywhere in the general area of unrest.

          Im not entirely convinced it will blow up, often times these Andean volcanoes seem to be mostly effusive. But I guess Santa Maria began its recent activity with a VEI 6, and the Quizapu volcano started off effusive and stayed harmless for decades before also doing a borderline VEI 6 although not a particularly intense one. But I think the chance of this doing an ignimbrite caldera right away are not very high compared to going into a more constructive phase.

          Thing about these Andean volcanoes though is that when things do eventually get to the point of collapse, it tends to be a big event, and if this place has not had a magmatic eruption since the Pleistocene that is at least a cause for concern.

        • I have some interest in how this situation could play out.

          As a volcanic system, I’d say it we shouldn’t consider it to be inactive. The stratovolcanoes could be extinct, but they seem to be satellite conduits of a deeper magma storage which could certainly make an intrusion and erupt. Intrusion here meaning dike, since there are multiple meanings to this word. So the complex I’d guess is alive. The stratovolcanoes might be dead. But are they? There are certainly some signs the conduit of Chiles is still intact, to some degree, there is shallow earthquake activity there. So my question is if the conduit of Chiles could be reactivated?

          The latest lavas of Chiles and Cerro Negro seem to have some extreme viscosities. Certainly upper end viscosity. None of those lava tongues seem to be less than 350 meters wide. Likely a crystal rich dacite, with the interstitial glass being high silica rhyolite, is my guess. I seem to remeber some volcanoes in the area have erupted crystal-rich dacites, if I’m not mistaken Quilotoa was one of them. For a magma like this it’s probably going to need a very large conduit to fit >100 meters wide. So I would expect an eventual intrusion would produce some massive bulging and deformation of the mountain.

          This is a TAS diagram of the Ecuadorian arc, not including some of the back-arc volcanoes, Sumaco, Sangay, or Reventador, which are mildly alkalic. Rhyolite doesn’t really seem to exist in the Ecuadorian arc, probably because no large upper level magma chambers exist where crystals can settle, all rhyolite melts are charged with crystals of more mafic composition giving them andesitic and dacitic compositions. I expect Chiles would be in the upper silica end. There were no Chiles-Cerro Negro samples in EarthChem, where I plotted the TAS:

          Regarding the future outcome, assuming it does culminate in an eruption, I don’t know if we should expect lava flows or a VEI 5-6. Thing is that in this sense silicic volcanoes seem to be very unpredictable. See Agung for example, the 1963 eruption started as a lava flow but then evolved into a VEI-5, the 2017 eruption was only effusive however. Quizapú is another enigmatic case, in 1846 it erupted ~5 km3 of magma effusively, in 1832, out of the same conduit and with the same magma, it erupted ~5 km3 in a plinian manner. Or La Soufriere which has alternated explosive and efussive, the 2020-2021 eruption started as a purely effusive eruption, however 4 months later it went plinian. I wonder if very small, hard to foresee differences, can determine whether a silicic volcano goes explosive or not. Although I should say that Chiles is probably more viscous that any of these three volcanoes.

          Of course we may get a Santa María and then a Santiaguito. Where there is a VEI 5-6 eruption and then a period of stratovolcano building starts. This is a very common thing to do for silicic volcanoes.

          • Hector, I think you’re missing a big part on Ecuadorian volcanism.

            There not only is Rhyolitic volcanism present in Ecuador, there is a lot of it. In fact, there is what popular media would describe as a supervolcano that has got pretty much zero attention from the doomsdayers in Chacana. And nearby Chacana, there are other slightly smaller, but still large rhyolitic calderas. Those being the Chalupas caldera system (closest to cotopaxi) and the little-studied Cosanga caldera.

            Read about them here -https://iopscience.iop.org/article/10.1088/1755-1307/3/1/012007/pdf

            And specific to Chacana here –

            https://www.researchgate.net/publication/249231131_The_Chacana_Caldera_Complex_in_Ecuador
            https://volcano.si.edu/volcano.cfm?vn=352022

            Cotopaxi even has rhyolitic volcanism in a bimodal manner, although it’s predominantly andesitic. I believe Antisana is actually a ring fault feeder volcano from the Chacana system.

            And here is some info on the Chalupas Caldera for reference – https://www.frontiersin.org/articles/10.3389/feart.2020.548251/full

          • Then again, I suppose these would count as back arc volcanoes from what you’re suggesting, so I would assume you’re not including them as a result?

          • Hector Sacristan: Thank you for the detailed response too the Chiles activity.

            Some of my thoughts from you reply: I feel like you might be right about the possible onset of an extended period (10^4-10^5 years?) of stratocone building as a possible outcome to this unrest if an eruption does occur. A stratocone initiating eruption might resemble a multi year andesite eruption such as Soufriere Hills, and end up being the first of dozens more to build another cone like Chiles.

            A less likely Hyaputina or Santa Maria type plinian event might be large enough to form a caldera but it would probably by a small ~2-3 km ? one. It seems like a VEI 7 Crater Lake style caldera is unlikely, but if it did occur it would more likely feature phenocryst poor ~10 vol% ? rhyodacite or low silica rhyolite. Two things that make me think that this is particularly unlikely (besides global frequency relative to VEI 6 sized events) is the seeming lack of these features compared to some arcs such as Japan or Aleutian. Another possible issue is that many of the larger VEI 7 type calderas seem to have pre caldera leaks of smaller volume but similar evolved chemistry resembling the early products of the caldera forming eruptions. These smaller eruptions or leaks seem to occur sporadically in the millennia before the climatic caldera forming eruption. I am not sure if all of the calderas of this type have these geochemically evolved pre-caldera leaks but the lack of such a feature at Chiles makes me wonder if such a scenario is particularly unlikely here.

            If a potential VEI 7 large caldera >8 km forming system was developing under Chiles, the first new eruptions might be small and feature phenocryst poor rhyodacites or rhyolites and signify a developing system that might not form a large caldera for many thousands of years. Mazama featured a VEI 7 Caldera tens of thousands of years after the end of andesite-dacite stratocone building, but featured a few infrequent leaks and smaller plinian events of phynocryst poor rhyodacite over 20,000 years or more leading up to the climatic caldera forming eruption. These smaller events also largely filled in the long time gap between the cessation of stratocone building and much later caldera formation.

            For some reason this type of VEI 7 arc caldera, often hosted by pre existing stratocones, rarely seems to form from phenocryst rich dacite. A posible exception might be the ~ 40 ka Inararo event, the first and largest Pinatubo caldera forming eruption, but I do not know of any other examples. Similar phenocryst rich dacites seem to feed some of the giant VEI 8+ resurgent calderas, but not the VEI 7 sized stratocone hosted calderas for some reason.

            Finally, the presence of a powerful, long lived geothermal system around Chiles made me wonder if the intrusion causing the current unrest might reflect a long lived system, possible extending back to the time of stratocone growth, that has been unable to produce any new magmatic volcanic products due to aggressive quenching and convective heat removal by the powerful long lived hydrothermal system. If this turned out to be the case, it might argue against any magmatic eruption near Chiles in the near geological future.

          • Cbus, you are right. I avoided the bak-arc area because the chemistry there is more alkaline, but made the mistake of being too selective since I did avoid subalkaline rhyolite volcanoes, like Cotopaxi and Chacana.

            TAS of Cotopaxi:

            TAS of Chacana:

            Antisana has one single sample in EarthChem that is rhyolite. This seems to be a very localized area that has rhyolite however. A small scale silicic flare-up. Here I have selected the entire northern Andes area from Sangay to the group of Nevado del Ruiz, avoiding only the area of Cotopaxi-Chacana-Sumaco:

            There are just 2 rhyolite samples. Almost all of the samples are basaltic-andesites, andesites or dacites. The trachyandesites are probably Sangay, Tungurahua and some other back-arc volcanoes.

            Another strange thing of the Cotopaxi area is Sumaco volcano. Sumaco erupts basanites and tephriphonolites. It is the most alkaline volcano of the Northern Andes, and maybe of the whole Andes, where such magmas are almost entirely absent. Cotopaxi and Chacana themselves are also more alkaline than most Northern Andes volcanoes, although the difference is small.

            Glenn Rivers, it does seem like volcanoes with crystal-rich magma don’t do large calderas. It is very common for crystal-rich dacites to do 2-3 km wide calderas with low-end VEI-6 eruptions, Quilotoa and Pinatubo being great examples. Such volcanoes also seem to do them recurrently, with long quiescent periods in between the eruptions. They do not seem to produce purely ignimbritic eruptions either, although they do feature large scale PDC/ignimbrite activity they alternate with fall deposits.

            Crystal poor magmas often do way more violent caldera-forming eruptions, which after an initial tephra fall activity evolve into an pure ignimbrite activity, consisting of an extensive thick pyroclastic flow deposit carrying either pumiceous or spatter material. Crystal poor rhyolites are often responsible for the largest calderas in the planet.

          • Interestingly each volcano arc segment of the Andes has its own silicic flare-up, near the end of the segment. There an association between the calderas and back-arc alkaline volcanics.

            The Southern Andes does its flare-up in its northern end. The calderas of Calabozos, Laguna del Maule, Diamante and others, which are transitional between subalkaline and alkaline. The back-arc features the massive Payenia Volcanic Province of alkaline lava, with trachytic Payún Matrú and Auca Mahuida, among many monogenetic alkali basalt volcanoes.

            The Central Andes is not so clear. The entire arc has seen large ignimbrites within the past 20 million years, all of the arc shows transitional compositions between alkaline and subalkaline with little variation, as well as active back-arc volcanism. However the youngest ignimbrites, Cerro Blanco and Incapillo are in the southern end. This is also likely the location of the most vigorous back-arc volcanism, with the extensive Antofagasta Volcanic Field and young Cerro Galán caldera.

            The Northern Andes concentrates its alkaline back-arc volcanism in its southern end. With the row of alkaline stratovolcanoes, Reventador, Sumaco, Tungurahua, and Sangay. This is also where the few rhyolite lavas and calderas are located, with Cotopaxi and Chacana.

            Interesting patterns show up.

        • A very interesting case is the Chao lava dome, which is among the highest viscosity lavas I’ve ever seen. Chao has 67-69 wt% SiO2 and 40-45 % phenocrysts. So it is a crystal rich dacite. It erupted 22 km3 of lava effusively, plus ~1 km3 of pyroclastic flows, which probably came from the collapsing lava front.

          https://media.sketchfab.com/models/3e473f5c5762494884953810d3f84975/thumbnails/0ab5192a0e7b452fbdda0649c546f798/11acee23db104e3e8d6293e3288f4ce8.jpeg

          There are actually many examples of highly viscous well-preserved lava flows, probably crystal-rich andesites and dacites, with little evidence of tephra around them, in the Central Andes. Usually lava flows that are relatively isolated. Some stratovolcanoes with similar lavas, instead, have a lot of evidence of explosive activity.

          • Whatvis the most silica rich magma that is erupting today? Nyiragongo is the most silica poor (Lengai isnt a silicate melt so I dont count that in this context) but there has to be somewhere that takes the other end of the line. I saw that Long Valley erupted rhyolite with 77% SiO2, which is even more than in most glass formulas. I doubt you could get pure quartz magma as that would need to be hotter than the mantle to melt at all but over 80% might exist. Pegmatite forms around granite from the very last bit of melt, pretty much just silica and incompatible elements, but I think it is only a plutonic rock.

          • That Chao lava seems to be about as silicic as erupted magmas get while still having >40 vol % phenocrysts…..into the rhyodacite territory. The more silicic lavas (true rhyolites esp high silica ones usually seem to be phynocryst poor. Interesting that ~23 km^3 erupted without caldera collapse. I suspect that this is because the volume loss in the magma storage area being compensated by the upward doming of ductile crystal mush and very hot lower crust (ultimately driven by gravity) instead of caldera collapse. This process may not be fast enough to compensate volume loss in faster pyroclastic eruptions.

          • Chad re: the most silicic magma erupted today…I do not know, but Novarupta started with very phenocryst poor ~1 – 3 vol% high silica rhyolite in 1912 (~77-78) % SiO2. I think it was actually quartz saturated with a trace amount of small quartz phenocrysts in places.

            In May 1980 the Mount St Helens cryptodome featured high silica rhyolite melt (~78% SiO2 or something), but the bulk magma was a dacite. The cryptodome was a phynocryst rich ~30 vol% dacite with a rhyolite ground mass to begin with. While the cryptodome was degassing for weeks under the north flank of St. Helens at a depth of several hundred metres, loads of microlite crystallization drove the remaining small fraction of melt to quartz saturation above 78% SiO2, causing the appearance of quartz microlites.

    • 15km from summit at 8km deep.

      I wonder if this was on a normal tectonic fault, but influenced by growth of the magma chamber. If this is volcanic, the depth to me does not indicate magma moving towards the surface so much as a blob of magma entering from deeper which has been causing the repeated swarms and swelling.

      • There is swelling of the ground to the southeast of Chiles volcano that has been going on for years. Also earthquakes have been happening 3 km below the summit of Chiles. The deeper earthquakes seem to happen immeditely north of the swelling, in faults triggered by the inflation. The big question is how much more magma reacharge can the rock hold before breaking or being pushed aside by the magma.

        • Agreed. I also think another question worth wondering about is how much old stale magma has been remelted / remobilized if an eruption were to actually occur.

          Interestingly, I found a surprising non-gated source of info from youtube here, where some researchers shared their INSAR findings from 2021 there. https://www.youtube.com/watch?v=9hk5QyUzfgA

          Their research seems to suggest the resurgence in the southwest of Chiles Cerro Negro is actually in the area of an old caldera called the Potrerillos caldera. I cannot find any information on this in a quick search, only info for similarly named calderas elsewhere in the world, but I would bet the source non-gated research paper likely cites more info on this.

          • Oh, and I forgot to mention, the supposed Potrerillos caldera is situated between Chiles Cerro Negro and the old/extinct Chalpatan caldera, which is buried a little further to the east.

            I took a screenshot from the video to provide some context. Definitely a bit fascinating – it would seem that the Potrerillos caldera is potentially the deeper feed source for the Chiles Cerro Negro volcanoes?

          • I won’t spoil anything from my article but things are looking are pretty ominous.

          • The idea of a volcano so incredibly long dormant (160,000 years?) waking up in our lifetimes to an unknown degree, is exceptionally fascinating.

            I really hope everyone in the vicinity can get to a safe distance if this is, in fact, waking up.

            But it’s really wild to think we may bear witness to this resurgence. Before Pinatubo blew the USGS had a pretty good idea that a large scale eruption was possible (aided I’m sure by the recent findings of tephra from its past events). I suppose that’s not really possible here, but is there any word on the scale of what we’re potentially dealing with here? The run up seems quite protracted and intense. Vesuvius had a couple decades of activity prior to 79AD too though, no? I guess with every system being different it’s hard to directly compare.

      • Yes, about tectonic faults. I think that magma movement can cause activity on existing tectonic faults even if they are at some distance from the intrusion. In the early recorded unrest at Pinatubo there was a diffuse cluster of high frequency tectonic or VT like events to the NW of Pinatubo, out some distance from the Buag period summit dome. There was a smaller cluster of VT events under the summit but the NW cluster was dominant I think. The location of that NW cluster was probably due to Pinatubo causing loading on that tectonic feature. I wonder if something vaguely similar might be happening at Chiles.

  9. Excellent article series, Jesper! I don’t know why, but Nyiragongo somehow always failed to interest me. That surely has changed now.

    • Thank you, yes its a very intresting volcano, Despite Nyiragongo Maybe not be very big, and it cannnot do a Leilani or Holuhraun in scale, but it remains one of the most hazardus volcanoes on the planet

      And its magma composition is indeed very unusual and at current its also one of very few extremely active volcanoes outside Hawaii togther with Nyiramuragira. ..

      Working on Part 4 that Will be the last and most complicated part to write .. writing the introduction to that.

  10. Lots of activity today. An M7 earthquake near Pinatubo. An M4.5 or so at Pahala – this is becoming more intense and now seems to separate into two clusters. And is there a flank eruption in the making at Loihi?

    • Loihi have clearly not entered the main shield building phase yet .. otherwise it woud erupt all the time like Kilaūea .. But it woud be fun If it will erupt now .. better they send a submarine.. still Loihi is more thoelitic than alkaline so it have already left .. the embryonic stage, and its already gigantic compared to any land volcano, in the near future when Kilaūea grows into a behemoth with both above the sea, the Loihi will be a Hualalai like thing sourrounded by Kilaueas lava flows .. Im not soure If Lohi will grow into a monster ( Kilaūea will in 100 000 years ) .. probaly another lohi Will form soon as well that Will be the next monster volcano after Kilaūea

      • Loihi and Kilauea are not really all that different in age apparently. Kilauea is older but it is not really known when it actually began, not is the true age of Loihi, the shield stage of Kilauea probably began only about 50,000 years ago, and Loihi probably has already started too but not completely. Both of them are way younger and closer in age to each other than Mauna Loa.

        I think an important difference is that Loihi began deep underwater not far from the actual base of the Island so that despite being over 3 km tall is still 1 km below the surface, where Kilauea probably began in shallow water 1 km deep or less and reached the surface quickly. By the time it was the same age that Loihi is today Kilauea was probably already very established subaerial. Mauna Loa at that time seems to have already been as big as it is today. I think though another factor in Loihi still being deep submarine is that Kilauea has not grown southwards at all, only eastwards really so far, if it was more evenly distributed and the south flank Hilina area was more regularly surfaced then Loihi would probably at least be near sea level if not already on the island.

        • It’s intuitive, I guess that if the plume is increasing its output it stands to reason that the individual volcanoes are going to be closer together and therefore will start off at a higher elevation. Hualalai might have started off subaerial on the shoulder of Mahukona, and Mauna Loa followed suit on Hualalai. On the Kea trend, Mauna Kea used the Kohala rift zone to jump start its growth.

          • I dont know about starting off subaerial but at the least most of the other volcanoes probably started shallower than Kama’ehuakanaloa. Mauna Kea could have been subaerial though from the start, but given how close it is to the rift zone of Kohala I still wonder sometimes if they are one system that had a summit shift, usually the rift zones at least on the surface avoid the beighboring volcanoes but Mauna Kea is closer to the trend of Kohalas ERZ than that section of rift was to Kohala itself.

            As a comparison the modern volcano of Hualalai is apparently a recent construction entirely under 100,000 years old, the original shield stage Hualalai had a summit that is under the saddle between it and Mauna Loa today and now deeply buried by lava from both. Maybe Mauna Kea is a late stage satellite of Kohala in this same way and that it has grown to obscure its parent. The volcanoes might all follow a broadly similar life sequence but there should be a lot of variables that can make them all individually unique. Kilauea could well do this given it seems to already posess at least two satellite volcanoes on the ERZ.

    • The Pahala quakes have been two clusters for a while I think, just now the distinction is more visible. The one that is further north has only formed since 2018, it might be coincidence that Kilauea erupted that year too but even HVO doesnt really know yet. About half of the northern cluster shows up on the Kilauea seismicity diagram and seems to be a flat line that gently curves up towards where Kilauea is, even if the area isnt the actual deep source for Kilauea there does seem to be a magmatic event there and it is moving towards Kilauea.

      The other cluster, it might be related to all 3, or it might be where the second swarm came from if it is an intrusion. Even if the quakes are moving faults something has to be making them move and Mauna Loa has not been doing anything particularly interesting.

      Would be interesting if there is an eruption on Kama’ehuakanaloa, the quakes are all pretty deep still though around 10 km. I think it will erupt before Mauna Loa does though.

    • Indeed. I have to say I thought he had dies a decade ago. He was over 100.
      Although I disagreed with much of what he said, particularly initially, he was a true scientist who considered contrary arguments and was thus to be lauded.
      There is no doubt his early works were influential, of often seriously misunderstood.

      • I heard an interview with him done when he was 100. He was brighter even at that age than most scientists. Very sharp brain. And a realist. He was clear we cannot manage without nuclear energy, even when much of the ecology movement was based on his work. Because of Lovelock we see the ecology of the Earth as a linked system with feedback – change something and everything will respond, including (eventually) the non-living aspects of Earth.

        • Problem is, what Nuclear Energy do we want to use? New nuclear power plants would not be ready to go into power generation for another 15-20 years, which would be too late. Also it would have to be alternate types of reactors since the standard designs do not work well in the increasing number of heatwaves we are getting. Many nuclear power plants had and have to cut back their output because the rivers were getting too warm to supply water for adequate cooling. Also nuclear energy only makes up a fraction of total energy generation when seen globally…..going nuclear would be insanely expensive. We are imho too late to make this decision. Nuclear is not the way to go and alternative reactor types are noch yet ready for mass production. Uranium itself is a finite raw material. And there is still no solution for long term storage. And the list goes on…..

          I want to stress that, since this is such a touchy subject, I am not at all against nuclear power per se. But in the state that we are in it is simply not a solution, not even in part.

          • Molten salt thorium reactors are something woth potential, generally speaking they should be a lot safer as the material is only fissile in very specific conditions, as opposed to water cooled reactors that are basically teased to the point of near disaster and only safe as long as they can generate excess power to run their own pumps… As I understand most uranium nuclear power plants are basically factories for bombs that are run at high rate and generate excess heat.

            Molten salt reactors are in some ways a bit more like the promises of fusion, where a failure of the reactor will stop the reaction passively. Of course the liquid is about 1000 C and highly radioactive, but nuclear reactors are some of the most overengineered buildings out there, which is part of why Chernobyl was such a big deal as the indestructible was destroyed…
            Thorium is also abundant and presently mined in large volumes acvidently as a byproduct of lanthanide production, where it is badically sitting around as a refined waste material. High level waste also acts as a fuel in such reactors. But you cant make bombs with them so no one is going to put money into it… 🙁

            It also, realistically, is probably too late to drop everything and build enough of these to replace grid generation fast enough, and the same applies to fusion no matter how good it will be once available. Despite the difficulties and certain inconveniences solar and battery storage to back up renewables is probably the thing we should be building en masse. If there is a silver lining to what Russia has done this year it has shown how poorly structured and vulnerable a fossil fuel economy is and rapidly accelerated the timeline of progression away from it.

          • Sure, this has never been an easy discussion. Lovelock thought we could not manage without it. Others who look at the total energy picture tend to agree. Those countries that have abolished or reduced nuclear (Germany, US) have replaced it with coal (!). We have immediate problems and long-term problems. That requires a major 20 year investment (which is what the Koch brothers tried to stop) to be able to switch our supplies, and we need to make sure the lights don’t go out in the mean time. We do not always need to build new reactors: the old ones are still there. We need to reduce energy usage. We need to insulate houses (the UK government in its infinite wisdom (this is a joke) stopped its house insulation program and is now deeply regretting it – it turned out not to insulate cost far more than the savings they tried to make). Bluntly, you cannot run a world with 9 billion people in a way designed for 2 billion, and we waited far too long. Lovelock saw that and saw that idealistic decisions (end nuclear) lead to disaster.

          • The problem of most new nuclear timeline is regulatory. This can be shortened considerably with unified reactor design that has already proven itself to regulators. That is the entire goal behind the small modular reactor efforts – a scalable system with pre-set approvals that can be placed as needed. Of course, this entire program is probably 15-20 years out right now – but then it would make things relatively easy to install.

            As for Uranium supply, it largely depends on cost. If fuel costs can be 2x higher and still worth it, there’s a near infinite supply of Uranium – sea water. Japan has been leading a multinational effort to “mine the sea” and basically scrub the water in the current flowing past the island for useful materials dissolved in the ocean. It’s a very interesting approach with technologies developed to imitate kelp and other creatures that basically have a high surface area to contact as much flowing water as they can and take the nutrients they need.

          • Indeed so. Also alternative nuclear reactions (eg thorium and plutonium) would take too many years to make into viable commercial systems. The biggest problem with nuclear is not waste (amounts are actually quite small in global terms) but the risk of terrorist attacks which means you need one big and well protected plant not many small ones (which would work better).
            I am pleased that I saw mentioned in the press for the first time the two major problems with fusion. One, where to get kilos of tritium reliably and safely and two the realisation that vast amounts of high energy neutrons are produced which would probably seriously degrade the innards and make them ferociously radioactive in a very short time. As a consequence I don’t think it will ever become viable as there is no real way to stop the inner casing absorbing neutrons and being transmuted into all sorts of other elements (mostly radioactive) that would not help the alloy properties on the inner casing.

  11. Some changes to the Mars sample return mission just announced – instead of a sample retrieval rover, 2 upgraded “Ingenuity Class” helicopters will be sent to act as a backup to Perseverance’s own ability to deliver the sample tubes. The biggest innovation is that the new helicopters will have motorised wheels so they can drive on the surface as well as fly! Not forgetting a hook to drive over and pick up sample tubes.

    Ingenuity itself should return to flight in August all going well.

    https://www.nasa.gov/press-release/nasa-will-inspire-world-when-it-returns-mars-samples-to-earth-in-2033

    NASA Will Inspire World When It Returns Mars Samples to Earth in 2033

    NASA has finished the system requirements review for its Mars Sample Return Program, which is nearing completion of the conceptual design phase. During this phase, the program team evaluated and refined the architecture to return the scientifically selected samples, which are currently in the collection process by NASA’s Perseverance rover in the Red Planet’s Jezero Crater.

    The architecture for the campaign, which includes contributions from the European Space Agency (ESA), is expected to reduce the complexity of future missions and increase probability of success.

    “The conceptual design phase is when every facet of a mission plan gets put under a microscope,” said Thomas Zurbuchen, associate administrator for science at NASA Headquarters in Washington. “There are some significant and advantageous changes to the plan, which can be directly attributed to Perseverance’s recent successes at Jezero and the amazing performance of our Mars helicopter.”

    This advanced mission architecture takes into consideration a recently updated analysis of Perseverance’s expected longevity. Perseverance will be the primary means of transporting samples to NASA’s Sample Retrieval Lander carrying the Mars Ascent Vehicle and ESA’s Sample Transfer Arm.

    As such, the Mars Sample Return campaign will no longer include the Sample Fetch Rover or its associated second lander. The Sample Retrieval Lander will include two sample recovery helicopters, based on the design of the Ingenuity helicopter, which has performed 29 flights at Mars and survived over a year beyond its original planned lifetime. The helicopters will provide a secondary capability to retrieve samples cached on the surface of Mars.

  12. https://www.usgs.gov/observatories/hvo/news/volcano-watch-hualalais-wahapele-eruption-cone-building-explosive-phreatic

    HVO Volcano Watch today is about Hualalai and the only maar crater in Hawaii 🙂

    Also a number that I have been looking for, its magma chamber. Both that it does have one and the depth it resides, 20+ km deep and still erupting from there with barely a day of warning… It is like the Hekla of Hawaii, actually it bares more than a casual resemblance too. Given the more alkaline magma too its lava is probably more gas rich and maybe even more fluid than the lava of its more active kin, although I dont know how alkaline it really is today and it might well only be in a relative sense compared to Kilauea. Still there is a cone near the saddle with mauna Loa that was created by hawaiian type lava fountains at least 1 km tall, which is rather a lot more than Kilauea and Mauna Loa.

    • Hualalai is much lower in Sio2 than Kilaūeas 50% Hualalai is on the edge of being a Basanite its Basanite / Tephrite acually very similar to Nyiramuragira and many La Palma flows and probaly hotter than Nyamuragira. About 42% Sio2 for Hualalai and its viscosity will depend on temperatures. The 1800 s flows are estimated To be erupted at 1150 C / 1140 C so not that diffrent from Puu Oo s pahoehoe and Will be more fluid than Puu Oo at same temperatures

      I been To Hualalai many times and yes the lava is very fluid, the 1800 s channels haves paperlike sheets of pahoehoe overflows and the pahoehoe near Kona AirPort is amazingly fine and delicate, another sign that it was a smooth and very fluid lava. Hualalais lava is darker and more glossy than Kilaueas, because of lower Sio2. But Halema’uma’u Thats 1220 C to 1250 C for Kilaueas summit is probaly just as fluid .. because of its High temperatures.
      But yes Hualalai is very runny at least the most recent two eruptions

      Hualalai will be insanely scary when it erupts .. : o

      • Halema’uma’u is probaly as fluid as Hualalai because of its high temperatures, Despite being a sillica saturated thoelitie.. but souch Thoelitic lava loose its viscosity faster than Hualalai woud do as both cool in an imagination experiment

      • I will have to get a car next time I go, so I can explore the rest of the island. Only really got to see a tiny bit, and all of it on Kilauea except for when I was in Hilo. I never actually saw Mauna Loa or Mauna Kea, they were completely covered in clouds…

        Hualalai is a poorly understood volcano. I think a lot of its comparisons are misleading, it is not very active compared to Kilauea or Mauna Loa but when you factor that most of its eruptions are pretty big it would probably count as a rather active volcano by world standards. It also has a god chance of erupting thsi century too, volcanic episodes lasting a few centuries and separated by gaps of up to 800 years are typical of at leas the past few millennia, and if 1929 is included then since 1650 there has been activity more or less about every century or less. Wahapele, which the volcano watch is about, was the last and probably largest of at least 6 eruptions from 800 to 1300 AD, a 500 year period, 1650 AD was only 370 years ago so it is at least very unlikely this series is over. The last two series also erupted between 1 and 3 km3 of lava, where the current one is presently most likely under 1 km3, so probably still some big stuff to come.

        • When on Hawaii 7 years ago we stayed near the mamalahoa trail just a bit north of the Kona airport. I asked someone how old that flow was and they said 4000 yrs. I have since heard it was 200 + and from Hualalai not Mauna Loa.

          • Flows right under the airport are from 1800 to 1801, the stuff around that might actually be a couple thousand though, he might have been very exact in his location 🙂

            But yes, still active, and unlike Mauna Loa which is only dangerous if it erupts in one area, Hualalai is about a 50/50, if flows north it is mostly fine, but go south then it is going to be La Palma #2 except it happens in 3 hours not 3 months…

    • https://www.google.com/maps/@19.6757639,-155.8296229,16z/data=!3m1!1e3?hl=sv

      One of my favorite Hualalai vents
      Explore it in Google Earth .. just imagine a 1000 years ago or a few 100 When it was active, fluid dome lava fountains in the crater with a big spinning pyrocumulus mini supercell above it lit by the nightglow and that kilometers long lava channel flowing likle a river .. for months perhaps, like a ribbon of liquid steel seem from afar it woud be an amazing sight

    • Hualalai is very mildly alkaline, transitional basalts, they straddle the division between tholeiitic and alkaline. There are a lot of pits in the volcano. Most them are sinkhole-like and probably fromed as rock collapsed into dikes and was carried away. Others may have had an explosive component though. It is certainly much gassier than Kilauea and mauna Loa. I don’t think an eruption would that dangerous though, maybe devastating yes, but the viscosity must be similar to Kilauea or Mauna Loa. I doubt eruption rates are higher.

      • Hualalai have lower Sio2 than Kilaūea and Mauna Loa
        But perhaps same viscosity just at sligthly lower temperatures ..

      • Eruption rates probably arent higher, but the slopes are way steeper, Hualalai has steeper slopes than many stratovolcanoes. Kailua Kona is way too close, if there is an eruption like Kaupulehu that goes in that direction there could be significant casualties given the whole thign could be as little as a day from first basal earthquakes to lava raging into town center…
        That is an extreme case, and 1929 shows that longer lived intrusions can happen (and also not erupt at all) that probably would result in more sedate eruptions. But then the volcano watch was about one of those ‘sedate’ eruptions suddenly turning violent and then becoming a lava flood afterwards, so its really risky for sure.

  13. Postshield events can be huge as well in Hawaii chain, Molokai have an enormous postshield vent at Kalaupapa Penninsula, 4 kilometers wide! and the vent is 1 km wide, its acually rather marsian in apparence, it too had a boiling dome fountain mess and feeding a lava channel souch vent eruptions are rather rare on that scale on human lifespann .. even much larger souch vents are the stuff that you see on Mars and Venus .. Kalaupapa must have been a rather very large eruption

    https://www.google.com/maps/@21.1996666,-156.9664884,14z/data=!3m1!1e3?hl=sv

  14. FWIW, the Icelandic authorities have entered the “let’s get people psychologically prepared for the next eruption” phase of their discussions about Askja, warning that “the drama queen” could erupt soon – probably measured in months or years, but possibly in as little as weeks.

    https://www.ruv.is/frett/2022/07/27/ekki-utilokad-ad-askja-gjosi-a-naestu-misserum
    https://www.ruv.is/frett/2022/07/28/dramadrottningin-i-dyngjufjollum-rumskar

    • Askja isnt that bad really, it did a big eruption in 1875 but that seems to have been the first proper rifting event and caldera formation there in millennia, most other eruptions on the fissure swarm seem to be more direct from the mantle and slower, and apart from 1875 it seems to only erupt basalt too. A bit like Katla the potential is there but happened too recently to be at risk of repeating yet.
      It will probably be quite photogenic though as eruptions there seem to be very intense, tall fountains. 1875 eruption was preceded by at least two basaltic ring fault eruptions in the couple years before the rifting began, curtains of fire 400 meters high and several km long.

      I dont know if we should be concerned about Oskjuvatn, it didnt do anything dangerous during the 1920s even when eruptions happened in it.

      If it happens in the winter though no one will see it 🙁 so either it happens before October or puts off for another year would be good 🙂

      • The ash may be problematic, though. Ash from the 1875 eruption made it to Norway, Sweden, Germany and Poland. Ash from Askja-S made it to Norway, Sweden and N Ireland. Ash + aviation + comms systems aren’t a great combination.

    • Read the extract. Evidently the authors tallied up the CO2 emissions from ongoing eruptions (entire oceanic rift systems included) and came up short to be the trigger for the warming event. UNLESS, carbon rich metasomatic crust got into play from decompression melt and added a large impulse of CO2.

      • metasomatic – altered rock,,, (metamorphic)

        I’m thinking something like a coal field that had been subducted in the past…

      • Wandering off… Flat Slab subduction, similar to what drives modern Popocatépetl, was likely at play in North America. Current ideas indicate that most of the now gone Farallon Plate is in a folded crumpled mess somewhere under the Eastern Seaboard. its not much of a reach to envision more than just oceanic crust was included. But even if it was, sea floor sediment collect carbon through marine snow.

        The cliffs of Dover are just one sample of that accumulation. Melt that entire strata and you would get a significantly large pulse of CO2 from the erupted melt.

        Caveat: Not a trained Geologist. And I did NOT stay at Holiday Inn Express™ last night.

        • Farallon plate is not entirely gone, the Nazca plate and Cocos plate is the southern half of it and the Juan de Fuca plate is also a remnant. The ridge is only partly subducted at the Gulf of California. Basin and Range terrain I think is in part because of the former compression relaxing and with no active pressure against the western seaboard the crust spread apart. The other part I think is Yellowstone, the basins all generally form a structure that almost looks like a bow shock behind the plume. Yellowstone is a very powerful plume, not as much as Hawaii, but probably comparable to what Iceland would be like if it was only the plume without the ridge. Erupt this year it will not but it is certainly not dead or dying.
          The Columbia Basalts are the combination of these, extending crust on top of a powerful plume. The basalts erupting in the wake of the plume are tectonically driven by the extesion but are chemically plume basalts.

  15. Bit of a clunk in Katla around 11:00pm Island time. 4.2 pretty much at the surface.
    I guess something collapsed in the caldera. Maybe melting ice and rock.

    • Katla’s on an off plate boundary rift. Could be the crust accommodating inflation to the north at Askja etc or west at the Reykjanes Peninsula? Possibly the latter? No idea what that would do to the magma under Katla.

  16. New earthquake swarm on Fagradalsfjall 🙂

    Looks like this place really is a bit of a repeat offender, what happened last year might not be the end of the story.

        • Actually the action is mainly 8-10 km deep. That puts it in the deeper crust, below the dike. There may be a bit of feeding activity

      • Was typing that other comment when this was posted 🙂 It is actually a bit more north than I thought, but still not at Keilir where the swarms last year began. It looks a little bit more to the right of where the 2021 eruption dike was too, same rift but different intrusion.

    • Havent seen a plot, but it looks like quakes go from generally being about 10-8 km deep to 5-6 km deep and only in about ah hour, it doesnt look liek there is too much of a long dike this time so maybe there is a conduit that is still there after 2021 and is being forcefully reopened, moving several km up in only an hour. Still pretty deep and the area is a rift, so might not be an eruption tomorrow but magma is definitely on the move.

      It is interesting though that these quakes are definitely at Fagradalsfjall, not at keilir. That whole fissure swarm probably has magma along it, the eruption last year rose up under Keilir and formed a dike that then erupted at Fagradalsfjall which was not directly over the feeder conduit to the dike, and that might be why it was fairly sedate. If the same thing has happened now but magma has directly gone up vertical to Fagradalsfjall, the eruption might well be quite a bit more intense than we saw last year. Probably not so intense as a curtain of fire like at Svartsengi or Krysuvik but something significantly more than the eruption last year averaged at. Might not be a great idea to be walking around up there right now…

      If there is an eruption too I expect lava will go a lot further, all the valleys are filled in last year, the same amount of magma will make a bigger flow field.

    • We may have a new dike growing. It has a volcano-tectonic earthquake distribution typical of intrusions. It is occurring in the general area where earlier two dikes started. If it develops into a linear swarm it will be practically confirmed to be a dike. When InSAR comes out and shows a butterfly pattern then we can be fully certain of it.

      And always remember earthquakes concentrate just under the dike, where the intrusion induces faulting. The top is largely aseismic.

      • This is too fast to be a new dike. It is related to the existing one. Note that you do get earthquakes on the top of the dike while it extends upward. That is happening here. There is a gap in depth around 7 km, which is where the old dike was at this location. Now it is breaking the ground above.

        • I wouldn’t say it’s that fast really. Dikes in Kilauea and Krafla volcanoes can take about an hour to reach the surface, and in that time they can cover multiple kilometres horizontally. This intrusion, in comparison, is really slow, it barely seems to have evolved at all since it started from what I can see. The December 2021 intrusion grew much faster horizontally, I seem to remember. If it doesn’t grow horizontally though, then maybe it is growing upwards, one would wonder if it will break out immetiately above where the earthquakes are happening then.

          • Manda Hararo in 2005-2009 might been a good analogue. Of the 13 dikes that occurred most of them failed to erupt. The first dike to erupt was fed by adifferent volcano Dabbahu, and was rhyolite, so is somewhat of a weird case. The other two dikes to erupt were small volume and located above the feeding point of the volcano. Short dikes near the feeder are more likely to erupt because they preserve more of their pressure.

            The December 2021 dike grew too far away horizontally and that may have been why it couldn’t erupt, lost too much pressure maybe. Although I’m speculating, not too sure how good of a rule this is, if the dike doesn’t really grow northwards or southwards then maybe it is much more likely to erupt directly above. Would certainly make sense if it was that way.

          • The earthquakes are still happening where they started. The rapid southward progression in seismic activity that was shown by the December 2021 intrusion is not happening this time. At least not yet.

    • The January 2021 dike intrusion it’s early stages. Yellow earthquakes are the first ones, dark orange the last. The swarm location roughly coincides to the one we have now:

      • That intrusion was in December, not January. I got a little too excited there I suppose.

      • This swarm is really intense. Enough to keep the tremor plot at a constant high level. Usually during a swarm you get both low and high readings, causing the tremor plot to become a broad blue line. Now it’s quite narrow at a constant high level. That could mean tremor, but I don’t want to be the one to make that call.

          • To be honest, a few days before Fagradalsfjall erupted in 2021, there was no earthquakes to the point people thought an eruption is not going to happen. Maybe we shouldn’t watch for more intense earthquakes but maybe watch for an end to a swarm. Maybe the magma went through the cracks after the cracking is done.

          • The quakes stopped when it was really close to the surface, probably within 1 km. I guess the crust was too thin by that point to break with the force to make an earthquake.

            I do wonder if that was because the eruption was slow though, and a faster eruption might be a little more noticeable.

  17. What are the odds of Fagradalsfjall, Katla and Askja each erupting before Christmas?

    & we should not forget the Vatnajokull contenders 😮

    • Askja is a part of Vatnajokull, at least the central volcano is 🙂
      I think probably only Fagradalsfjall has a safe chance, we know how long intrusiosn last here now so if there is an eruption out of this it will be before September. The others are way too early t oknow how quickly an eruption will take place I think. Askja might suddenly have a small eruption right now or not for ages. Katla is not open, it will be quite clear something is happening.

      Grimsvotn is going to always be mysterious, if it was only on pressure and statistics it should have already gone by now, so it is clearly much more complicated than our models. Hekla is basically dormant or erupting I guess.

      • Askja is inside the boundary of the Vatnajökull national park, but it’s well outside the glacier itself.

        • I mean it is one of the big volcanoes that is primarily driven by the plume, just being the only active one that is not under the glacier.

  18. Big swarm now at Fagradalsfjall, and it is forming a stack. Not at eruptible depth (yet). The largest quake so far is about M4, with 5 stars. They are not being checked so smaller quakes will have uncertain depth

      • The interesting thing is that is started with deeper quakes (10km) 5 hours ago, before this sudden reactivation.

        • Maybe another source, perhaps new, besides the one at Kelier? (or is it the same spot?)

    • Well, anyways, looks like the 3 to 4M’s might be either magma or a faultline cracking the crust possibly.

  19. Yet another 4.4 for today.
    Saturday
    30.07.2022 16:52:24 63.918 -22.225 3.4 km 4.4 99.0 3.0 km NE of Fagradalsfjall

    • You are welcome! First comments are always held back by the system for approval (sadly this is necessary). Future comments should appear without delay.

  20. Fradalick Action! Well, nearly. Latest look at the charts show a 3.4mag at 3.2km deep (99%). Looks like something’s cracking rock and creeping up. Time to get the popcorn out and wait (and wait…and wait).
    I’ve re-bookmarked my webcam links.

    • Sigh. I really should be less excitable. “Fagradalic” action was what I had in mind…

        • Sorry, Merlot. I tried but my small brain can’t get the joke… Please put my mind at rest.

          • Hi Clive,
            In the big coverage of the last eruption by Rekjavik Grapevine.news channel. The main presenter generally turned up with his dog Polly for broadcasts.

            I hope this helps.

          • Of course, now I remember. I remember Polly his ‘assistant’.
            Thank you for putting me out of my misery 🙂

  21. 16 stars ar Fagra just till now 12 checked, stars becoming shallower to 3 km below, M4.4 draws attention the most.
    Looking at the lowpass drumplot that one lasts more than four minutes. Something is moving. Worth to follow this swarm! About 600 quakes in the IMO table.
    The centre of the stack seems to be about 2,5 km northeast of the craters of the 2021 eruption.

    Credit graph IMO

    • I’ve been idly watching the crater. It looks like rainwater seeping into the walls is contacting hot rock and steaming out. It’s been smoking on and off there since the eruption stalled.
      But is it my imagination, or is that steaming becoming slowly more intense? I’m interested in that point on the crater wall because close to it was the minor secondary vent that appeared during the mid to later parts of the main eruption.
      It’s so hard to call. Would a new intrusion remobilise a semi-open conduit? Or make a new path? Or will it settle down and go to sleep for a couple of months?
      I’ll munch on my tranquillizers as I sit on the edge of my seat.

      • I have been watching for the past 10 minutes Clive and it definitely is increasing. I havent been watching this video linl for around 6 months though so perhaps it is just increasing as the temperature is dropping in the evening/night. I shall stay and watch for a bit , just in case,,,,,,

  22. From IMO’s Frettir webpage, google translated.

    Jarðskjálftahrina á Reykjanesi
    30.7.2022

    “”At noon today, a powerful earthquake series with a lot of small earthquake activity started just northeast of Fagradalsfjall, a short distance north of Fagradalsraun. The largest earthquake of the series was measured with a magnitude of 4.0 at 2:03 p.m. The earthquakes are now being measured at a depth of about 5-7 km. Skjálfts have been found in Reykjanesbær, Grindavík, in the Cape Town area and all the way up to Borgarnes. It is believed that these letters are due to a magma flow that is taking place northeast of Fagradalsfjall at a depth of 5-7 km.

    Because of the avalanche, there is an increased risk of rock falls. Several earthquakes have already been measured above magnitude 3, and in earthquakes like this, rockslides and even landslides can occur. There have been no reports of recent rock falls in the area yet. If there are more powerful earthquakes, the probability of a rockfall increases. People are advised to be careful on steep slopes, near steep sea cliffs and avoid areas where rocks can collapse. The National Police Commissioner in cooperation with the Suðurnesj Commissioner of Police has declared a level of uncertainty

    Civil Defense and VONA notification has been issued and switched to yellow for Krísuvík. The National Weather Service will closely monitor progress.””

    So, official conformation of a dyke forming indeed. 🙂

  23. If you look at the earthquakes over 2.0 for the swarm at Fagradalsfjall, there are some shallow quakes but also some very deep ones c. 38km which must be well into the mantle.

    • These are auto detected, when checked, history learns, most of them will be relocated long/lat and depth as well. Some of the checked (marked as 99% in the list) are shallow tough. Looking at the quakes list it is hard to say how the dyke is developing at this moment. The 3 km mark has been crossed few times though past hours.

    • Be cautious on this. The earthquakes have not been checked yet by IMO, and especially the weaker ones have uncertain or even wrong depths. The 38 km depth is unlikely and is most likely because of confusion with the many weaker quakes. There are some quakes just under 3 km depth. The swarm seems to be decreasing now.

      • The shallower ones have been confirmed but the 38s are still showing 90%. Guess I’d focus on the shallower ones right now too.

  24. Saturday
    30.07.2022 20:48:57 63.917 -22.214 3.7 km 4.3 99.0 3.3 km ENE of Fagradalsfjall

  25. Jesper – A great series of articles on Nyiragongo!

    Like you, I’ve always found Nyiragongo to be one of the most fascinating volcanoes I’ve read about.

  26. 35cm uplift at Askja, pretty significant amount albeit over 11/12 months. This one looks like it might erupt next

  27. Could be wrong, but there might be lava in the system already (could be wrong).

    I saw this on the Geldingadalur Volcano, Iceland LIVE! Close-up stream where they showed a kind of thermal thingy, where they show bright spots. Here are the times for them if navigating on the stream:

    00:18 – Eastern flank
    00:20 – South flank
    00:22 – Near Crater

    It could be older magma or something else entirely, but there is something going on there.

    • It it is lava you wont need a thermal cam to see it 🙂 Remember this place erupted what might be the hottest lava we have seen, some reports were for well over 1200 C, even 1250 C. Only other place that eruption atemperatures that high seem to exist otherwise are in lava lakes of tholeiite basalt composition and large dimension, which might as well be considered as an open hole in a magma chamber. Even at that temperatures of well over 1200 C in a historical eruption have only happened in Hawaii as far as I know, and in all cases there it was either a wude open conduit ( Halemaumau) or an eccentric eruption where magma basically bypassed the main magma chamber (1959, 1859). For eruptions that hot on land this is a first in Iceland.

      Especially now it is night, if an eruption happens it will look loke the sun. If the eruption happens right above the deep source then it might not be so small to start as last year was, not a lava flood but tall fountains might be on the table, it will not leace us guessing 🙂

    • Are 1250 C confirmed for the Halema’uma’u lava lake 2007 – 2018?
      Yes that was a very fluid lava If you look at this video: https://m.youtube.com/watch?v=gNoJv5Vkumk 11:01 – 11:11
      Based on fludity it looks like thats the case as high temperatures are very good at breaking down the Sio2 polymerisation. But here the color in daylight looks rather dull even with hot exposed lava surfaces, but coud just be the instant atmospheric cooling of exposed lava bubbles, fresh lava cools instantly on surface Making it difficult To read temperatures. But Its very runny for soure Halema’uma’u and Hawaiian lavas display extraodinary smoothness and fluidity even well below 1200 C. Based on its fludity and glassy look, I guess its a completely crystal free melt in the Overlook lava so it was 1250 C

      • Overlook was very fluid for soure, and the upper parts just below the glass skinn where so gas rich it had a density of water, an unlucky human woud sink like a stone in that If you hit at high speed

        • Not 1250 C at least in the conduit, although the lower chamber in well over that (1350 C, according to Mg concentration in 2018 olivine). But there are numbers of over 1200 C for the lake. I dont know how hot todays lake is, probably somewhat lower as it is only fed from below on one side.

  28. There is quite some quakes that are verified at between 2 and 3 km deep now, none shallower yet but it is really pushing up fast. At this rate it will actually erupt in the next day.

    I assume magma could actually be shallower, if it is forming dikes then it might well be basically right there. It seems unlikely at least now that an eruption will resume at the 2021 site, it will be a new spot.

  29. Looks like we have a 2 km long dike. I was looking at some old comments from the December 2021 dike, that one grew to 8 km lenght in 10 hours or so, then stalled. So the two intrusions are very different in lenght.

    I’ve been thinking about the Krafla and Manda Hararo sequences of dike intrusions and how they might enlighten us to what will happen.

    Manda Hararo graph:

    Krafla graph:

    Manda Hararo was mostly a non-eruptive event. Of 13 dike intrusions, 3 of them erupted. The d0 eruption was fed from Dabbahu not Manda Hararo. The two dikes that erupted and were fed from Manda Hararo, d6 and d12, were shorter and near the feeder of the dikes. There is also some tendency for them to erupt twards the end of the sequence.

    Krafla was 19 dikes or so. The most important eruptions happened among the last 7 dike intrusions. Those eruptive dikes were centered over the volcano caldera and had smaller volumes than more horizontally extensive earlier dikes. However there were also earlier dikes that did not erupt, despite having small volumes and growing in the caldera area.

    If it plays out similarly to Krafla or Manda Hararo I expect this dike has lower chances of erupting than not doing so. Mainly because this may be the start of a long dike intrusion sequence. Early on, the rock is easy to push away due to the tensile stresses built up over the prolongued quiescence, even with little pressure not enough to erupt an intrusion can happen. As dikes keep getting intruded it requires increasing pressure to rift, and this is when the dikes start overflowing and eruptions happen. Right now there might be too much tension for the volcano to erupt.

    Of course it may not play out the same as Krafla or Manda Hararo. The February-March 2021 dike intrusion took its time to erupt, but did eventually do so, after about a month of slow growth in a way that was very different to Krafla or Manda Hararo. The December 2021 intrusion was seemingly faster, it soon stopped inceasing in volume, in a way more akin to Krafla or Manda Hararo. So it if plays out again like the first dike it might erupt.

    • I wish they would set up tiltmeters next to the feeder location of Fragradalsfjall and made the data public, like the summit tiltmeter of Kilauea at Uwekahuna that shows the DI events so wonderfully. Tiltmeters did a priceless job during the Krafla dike sequence. GPS and InSAR just don’t have the same temporal resolution, or the precision to detect small local signals.

    • Wait a minute! I was so nervous that I pulled an old diagram from May, sorry. Here it is (ewesome action in Iceland).

      • Really nice. You can see how the blue and red clusters, which correspond to strike-slip faults, get gradually active as they react to the the dike intrusion growth. The dike itself, orange, seems to be dropping in activity gradually. Right now most earthquakes are happening in strike-slip faults away from the dike that are being forced to move.

        • The activity is clustered around the old fissures. Not the ones from last year but from tens of thousands of years ago. I only looked at a few quakes, admittedly. One cluster is around the north edge of Fagra, the other on the fissure east of Keilir. Those fissures are certainly not active. They are completely solidified. I guess what is happening is that the pressure on the rock is breaking to the old solid dikes away from the surrounding rock. Old dikes are rock-hard basalt. The surrounding rock may be a little more deformable. The contact is a weakness. I don’t think this is rising magma: it is pressure from a deeper intrusion. Of course, once the rock is broken, it is easier for magma to find a route up

          • I’m curious to know what your opinion is on last year’s dike. If the above are old hard rock fissures, we still must have some dike melt under Fagradals (excuse name inaccuracy). Could the dikes intersect? Or connect? Thus reactivating last year’s vent?

          • Dikes don’t normally cross. Old solid dike are hard and will tend to deflect the new dike upward or sideways. A recent dike is still molten/partly molten and can soak up the pressure. The new magma/dike will push in and join. But I would not say never.

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