Nyiragongo and its ultra alkaline magma – Part IV

One of the prettiest of all photos of the 2003 – 2021 lava lake of Nyiragongo. Taken by Oliver Grunewald as he visited in early 2010’s. Pahoehoe overflows on the crater floor, overflows from the perched lava lake. In this last article of my series, I will try to examine the behaviour of Nyiragongo’s nephelinite lava.

This is the last part of my article series, and it will be about the most complicated stuff: a look at the behaviour of Nyiragongo’s lava and how fluid it really is. In part three we had a look at how unusual its low silica magma chemistry is, and how this led to the famous media phenomena of Nyiragongo having “the fastest and most fluid lava on the planet”. In the last part of my Nyiragongo series we will have a look to see if that really is true.

The behaviour of Nyiragongo’s lava depends on many factors. The behaviour of viscosity is called rheology and that is a very complicated field of mathematical science, and especially for beginners. So in part 4 I will have a quick peek at the rheology of Nyiragongo’s lava. Rheology is a field that I am not an expert in either, so I will explain very simply below what determine viscosity in magmas. The behaviour of “ultrabasic” alkaline magmas is not well known, since they are so rare, that is why it is worth having a whole article on this

Nyiragongo viscosity discussion: how fluid is it really?

Nephelinitic pahoehoe from 2016 – 2021 intra caldera wall vent that was active together with the lava lake. While being compositionally alien compared to a basalt, its viscosity here does not seem different from hot near vent flows in Hawaii and Iceland. The high gas content makes a swollen look. Photographed by Torleiv Nordgarden during his 2018 visit to Nyiragongo

Before I discusses Nyiragongo’s viscosity it is worth to take a look at what determines magmatic viscosity. Knowing the factors that determines magmatic viscosity, makes it more clear to understand how complicated the question is that I am discussing in this article.

The main factors that affect magmatic viscosity

Silicate contents: Low silicate magmas like basalts are in principle always much much more fluid than the highest silicate magmas. Silica forms long silica chain polymers in the magmatic melt and that thickens up things. Low silicate magmas with little polymerization erupt fluidly and especially so if the temperature is very high. High silica magma can be nearly solid if the temperature is low when it erupts. Low silica content stops these polymers from making the magma sticky. Nyiragongo is the record holder for the lowest silica magmas among active silicate volcanoes.

Higher temperatures significantly helps to break down these silicate polymers in the magma. An andesite melt at 1100 C will be very much more mobile than an andesite at 880 C. A basalt at 1240 C will be very much less polymerized and liquid than a basalt at 1090 C. In basaltic activity, temperature determines viscosity and determines if you get hawaiian or strombolian activity.

Crystal Content also affects the magmatic viscosity. Most magmas are a mix of glass melt and crystals. A hot crystal-poor melt is smooth and flows easier without stress. A crystal-rich magma can become almost like liquid concrete or wet sand. Crystals thickens things up, and causes rough lava flow surfaces. A crystal-rich magma can be compared to liquid ice cream with a lot of hard chocolate pieces in it, while a crystal-poor magma is a warm chocolate ice cream where everything is liquid. Nyiragongo is generally poor in crystals, so rises freshly from depth.

Alkalinity (sodium, potassium content in minerals) in the melt helps too to lower the viscosity since alkaline minerals have lower/ less SiO2 polymerization chain bonds than subakaline minerals.

Water: Magmatic water lowers both viscosity and melting points. It loosens up the silicate polymer bonds as well as lowering the temperature at which magmas remain liquid.

As we learnt in part three, Nyiragongo’s odd composition gives it many good scores in having low viscosity when it comes to the factors above here. Nephelinites are generally very low viscosity magmas. But exactly how low Nyiragongo’s viscosity is, is rather complicated. I will now dive into that complicated question, after having a look at what determines viscosity in magmas.

Lavas that are as alkaline as Nyiragongo are a rarity, and you will not find a currently active example of this composition anywhere else on Earth. It is mostly composed of nepheline and augite as minerals. This was one of the ephemeral pahoehoe lava flow vents associated with the 2016 – 2021 caldera wall spatter cone vent that was in eruption during the 2003 – 2021 summit lava lake. Photo: Patrick Marcel https://www.youtube.com/watch?v=GmUqQe976E4

The 1977 example lava flood The 1977 eruption is a famous example. In 1977 Nyiragongo burst open, and very fluid, extremely fast moving lava poured down the flanks. Within minutes it got to settlements kilometers away. Eyewitness suggest it flowing at between 70 km/h and 100 km/h at the upper slopes. The flow passed the forests at such a speed that it did not set fire to the trees and even left some thicker leaves with a thin glassy layer. Some pahoehoes (smooth lava flows) close to the vents were only thin paper-like sheets of dark grey glass, at places less than a centimeter thick. Numerous persons, mostly the elderly or children, could not escape from the flows. Exact numbers of victims cannot not be confirmed. Although the official count was 74, it is assumed that maybe 400 people have died. The nephelinite flood covered persons and animals with a thin glassy carapace. A whole herd of forest elephants were all killed by the lava flood and encased in dark grey glass. Their hollow casts were later broken into to reveal their lava moulds. These elephant casts where photographed by Maurice and Katia Krafft. The trunk and feet were all visible in the lava moulds as well as their calcified bones.

Around 20 million cubic meters of very degassed magma from the upper lava lake conduit erupted inside of an hour, after which the eruption stopped instantly. A similar spectacle happened in 2002 and recently in 2021 when the magma lake column drained once again because of pressure in the magma column. The 1977 eruption is infamous and still reverberates through history as the first eruption to really show Nyiragongo’s hazards. The famous volcanologists Maurice and Katia Krafft arrived just 2 days after this eruption happened. They took almost all the existing color and black and white photos from the fresh flows at the eruption sites.

Photograph by courtesy of © JC Komorowski of the Goma Volcano Observatory. This is one of the fissures from the 2002 eruption, showing the extreme fluidity of this lava composition close to the vents. But very high eruption rates are mainly responsible for the appearance. These are real lava flash floods. Further from the vents it turns to Aa lava. The 1977 eruption and 2021 produced very similar flows close to the fissures. Similar fluidal features can be found in Mauna Ulu vent at Kilauea. The 1977 lavas where also degassed and appears less swollen and frothy than gas rich lava flows. Photo https://mhalb.pagesperso-orange.fr/kivu/eg/eg_4h_eruption_photo.htm. https://mhalb.pagesperso-orange.fr/kivu/images4-diapo/photo12.htm

The 1977 eruption can be thought of as a hole in a dam, resulting in a catastrophic drain-out. The lavas where extremely fast near the events and very fluid, but the magmatic liquid cooled and crystallized as it flowed down. The very high eruption rates strongly favours Aa lava flows (crinkly and rubble-like) and Aa lava forms indeed the majority of the flow fields of 1977, 2002 and the 2021 eruption. There may have been turbulent lava flow close to the vents, meaning there where lots of vortices in the flow, rather than everything flowing smoothly in the same direction. Turbulent flow regime is reserved for only the most fluid lavas, and was probably last seen in the huge surges in lava flow rate in Fissure 8 during the 2018 Leilani eruption

The 1977 eruption has been described as a typical Nyiragongo flank eruption, but the volcano can do other stuff as well. These historical lava floods 1977, 2002 and 2021 are events with extreme eruption rates because of the pressure of the high-standing lava lake magma column. The pressure from that pillar of lava and the volcano’s steep slopes is why these eruptions flows so fast. This mechanism makes Nyiragongo flank eruptions probably the most dangerous effusive eruptions on Earth. Nyiragongo’s steep slopes makes it a very different phenomena than gentle sloped Kilaūea.

The paper sheet thin lava flows near the 1977, 2002, and 2021 flank vents were also a result of the lava being very degassed and not frothy and erupting very rapidly. Lava which is low in gas forms much less thick deposits then gas-rich lavas. The 1977 lava was a degassed lava from the lava lake column, and resulted in deposits that probably appeared more fluid than they really where. But such fluid features near vents could not be produced if the lavas where very viscous. No volcanologists were on site when these fissures erupted. We will never know the viscosity of these near vent conditions of Nyiragongo eruptions. We can only do the stuff in laboratory.

The viscosity and rheology of Nyiragongo have been not extensively researched. The measurements that have been done in the lava lakes have showed a very low viscosity, that is in line with the lowest measurements from Hawaii. Temperature measurements are poorly recorded but seem to be a bit above 1100 C range from the summit. Viscosity of lava has a lot to do with temperatures as well as silicate contents. Many other alkaline magmas with low MgO contents and very low silicate undersaturated magmatic melts emerge at low temperatures and erupt as cold strombolian eruptions. An example of that is Oahu’s sugarloaf nephelinitic flow that emerged as a cold viscous crystal mush. Nyiragongo and Nyiramuragira may own their low viscosity to a combination of their exceedingly low silicate contents and relatively high temperatures.

As described in the introduction, temperatures can affect magma a lot even if their silicate contents are relatively high. For example, most normal non-alkaline andesites, dacites and rhyolites emerge at relatively low temperatures at around 860 C and some as low as 700 C. That is one reason they are so viscous. The low temperatures makes active silica chain polymerisation which clogs up the melts. The world’s hottest andesite is erupted by West Mata Volcano that erupts ultramafic high-silica boninite andesites at 1320 degrees C. When submarines filmed that eruption it flowed like fluid basaltic pillow lavas and channels. The same high magnesium andesite eruption on land with the same temperatures would be as fluid as Fagradalshraun near the vent despite its 60% silica. In ancient komatiite lavas, that are very hot, all silica polymerisation was broken down because of high temperatures. This created a melt viscosity as low as water, showing how efficient high temperatures are in breaking the SiO2 chains.

High temperatures also affect evolved magmas. Some rare rhyolite magmas that emerge at 1000 C can form highly mobile obsidian block flows that can move many kilometers. Fissure 17 in Hawaii 2018 erupted a very hot 1100 C andesite pocket that flowed just as easily as an Etna basalt, while Soufriere Hills erupted similar andesites at 820 C forming very blocky lava domes. Crystals also increase viscosity in cooler magmas when high melting point minerals freeze out forming a melt that is a lot like melted ice cream but with lots of hard chocolate pieces in it. Now we learnt that very high (rare) temperatures can affect even some higher silicious magmas.

So what about ultra-low silica magmas and Nyiragongo? Low silica magmas are generally the most fluid, as they erupt at lower silicate contents and higher temperatures than their more silicious relatives. Nyiragongo with the lowest silicate contents of all silicate magmas and relatively high eruption temperatures should have the lowest silicate polymerisation and therefore the lowest viscosity among silicate based melts. Measurements suggest it is one of the lowest, quite a bit more fluid than really warm honey in some lab experiments. That agrees with the flow structures during the 1977 eruption. But there are other hot basaltic contesters with low viscosity.

Photograph by Justin Kabumba / Associated Press) https://www.latimes.com/world-nation/story/2021-05-23/congo-volcano-eruption-ensuing-chaos-kill-at-least-15 The 2021 lava flows in Goma shows how temperature affects a lava’s viscosity. While Nyiragongo is extraordinary low in silica, far from the vents the lava flows became viscous Aa lava because of increased crystallization as the lava lost temperature. Nyiragongo’s Aa lava can still move at terrible speeds due to their low silicate content and the very high eruption rates with Nyiragongo’s lava lake drain-outs.

Nyiragongo’s magmatic origin with very small amounts of partial melting may give it a much lower eruption temperature than really hot basaltic eruptions. Kilaūea above the powerful Hawaiian hotspot challenges Nyiragongo with some the lowest measured viscosity silicate magmas on Earth. Kilaūea produces hot thoelite basaltic magmas from large amounts of partial melting. Kilaūea’s silicate content are much higher than Nyiragongo’s but the temperatures are also really high, sometimes in range of 1250 degrees at Halema’uma’u. As mentioned, high temperatures helps to break down the silica polymerisation resulting in measured Kilaūea summit viscosities that are in range of many of Nyiragongo’s measurements. But many of Kilaūea’s lavas especially at the flanks at the Puu Oo vent have been a bit more viscous than the Nyiragongo measurements.

Kilaūea’s summit is another example of a very fluid lava with exceptionally low viscosity. It has higher SiO2 than Nyiragongo, but has higher temperatures. If the lava is very hot then the SiO2 content becomes less important. Photography by USGS 2017

Nyiragongos ultrabasic alkaline magmas are perhaps the least polymerized on modern Earth. Nyiragongo’s lava would flow more easily than Kilaūea at the same temperatures. Most viscosity measurements of Nyiragongo lavas are a bit lower than typical fluid basaltic lavas and very much lower than higher silicate magmas. Many experiments been performed in laboratory furnaces, including some for Nyiragongo. Samples from Nyiragongo, Nyiramuragira were crushed and melted and stirred in furnaces. Similar experiments been done with rocks from other volcanoes. The Nyiragongo nephelinites where the most fluid when the magmatic furnace melts were at the same temperatures. Nyiragongo was easier to stir at lower temperatures than basalts at the same temperatures.

But it is also clear to me that very high temperature basaltic lavas in Hawaii and Iceland can have the same low viscosities. The lowest viscosities of all modern modern magmas could be a hot picrite basalt, since alkaline nephelinites are erupted typically at low temperatures. At high temperatures in many lab experiment basalts have been among the most fluid of all melts. Nyiragongo has generally been the most liquid at laboratory experiments. Nyiragongo’s rare mineral composition kept it much less polymerized than other samples.

The viscosity that have been measured in nature at Nyiragongo have been among the very lowest of all silicate magmas on the planet, with some of Kilaūea’s summit lavas being just as low. Sometimes temperatures is just as important as silicate content in determining a magma’s viscosity, especially for melts of basic and intermediate composition. Its worth noticing that the theoretical calculations for Nyiragongo’s melt viscosities have suggested viscosity of around 1 Pascal-second for Nyiragongo’s lava, but real world measurements in the lava lakes resulted in higher values at around 20 to 50 Pa-s. That is in line with the very lowest measurements from Halemaumau in Kilauea (20 Pa-s). The lowest theoretical eruption viscosity for Kilauea has been around 10 Pa-s with some hotter flows from Kilauea’s depths even much lower. Values below 10 Pa-s have also been suggested for some Nyiragongo flows. These figures for these two volcanoes are very low compared to almost any other silicate magma. Kilaūea’s summit can probably display viscosity below 10 Pa-s as well. Most other active basalt lava flows have viscosities in range of a few 100’s of Pa-s to over 10 000. And many more silicic lavas have viscosity that are much higher than that. 10 Pa-s is about same as lukewarm honey. The very high density of lavas makes them look more fluid than they really are. But the paper-thin sheets of lava spatter that can be found in photos with both Kilaūea and Nyiragongo’s lava lake walls may suggest viscosities below 10 Pa-s, making these two volcanoes perhaps capable of having lava a bit more fluid than honey.

The few laboratory furnace experiments that have been done on Nyiragongo-type rocks shows very low polymerization. The 2003 Jacques Durieux summit lava lake samples shows no crystal formations at all and only gas bubbles. Such pure liquidus Nyiragongo magmatic melts have been simulated under laboratory furnaces and shown to have very low viscosities. The pure melt viscosity for Nyiragongo is around 1220 C, the temperature needed to melt all mineral components. Most of the other Nyiragongo samples I have been reading about have been a bit below this full liquidus temperature, with tiny white crystals of nepheline present – as mentioned, like melted ice cream with some small hard chocolate bits in. A magma below its liquids temperature will be more viscous than its full melt temperature, although being very silica undersaturated clearly helps to keep its viscosity low even below the full liquidus temperatures.

Nyiragongo’s strong silica undersaturation allows it to move quickly even at sub-liquidus temperatures according to the lab experiments above. That is the reason why Nyiragongo lava flows were able to flow may many kilometers in the 1977, 2002 and 2021 flank eruptions without loosing a lot of speed, because such a strongly silica undersaturated lava, does not saturate a lot with silica as it cools and crystallizes. In other words a more crystalline nephelinitic flow does not have a notable higher SiO2 content in its glass melt than a fresher crystal poor one (although increased crystallization raises viscosity). It is this that explains why Nyiragongo’s fissure feed Aa flows can race forward at terrible speeds even if they are undercooled and crystal rich, because the remaining glass melt are SiO2 poor as well. Because of that the lava was able to flow great distances before significantly cooling and succumbing to the rheological barriers of crystallization and cooling.

Such behaviour is quite different from more normal basaltic lavas, that rapidly clog up as they cool and crystallize and their SiO2 saturate as the lava flows loose heat.

Both Nyiragongo and Nyiramuragira silicate rocks (nephelinite and basanite ) have been melted in furnace experiments and their viscosities compared. Nyiragongo is a bit more fluid even if it has undercooled conditions, thanks to its lower polymerization. The viscosity of both volcanoes are low but in line with hot hawaiian lavas. Nyiragongo’s viscosities been slightly lower in experiments with batches from both at the same temperatures, but the difference is very small.

Nyiragongo remained less crystallized at lower temperatures than Nyiramuragira in these experiments. Nyiramuragira’s lavas also had higher total liquidus temperatures than Nyiragongo’s composition in furnace experiments. Nyiramuragira is richer in silica and poorer in nephelinite and other sodium bearing minerals than Nyiragongo is. Most other research on past nephelinite volcanism in Lengai and post shield flows in Hawaii have found that the flows where viscous and crystal rich, so Nyiragongo is perhaps unusually hot for being a nephelinitic melt.

It is a question thats hard to answer

The very interesting question that I am looking at in the text is ”is Nyiragongo the most fluid silicate based magma”? Magmatic fluidity has a lot of different factors that have to be taken into account. Lava is an incredibly strange fluid, it is a mix of molten minerals. Viscosity goes down with increasing temperature and lower silica content. A combination of both would be best. Most alkaline magmas seen in historical times appear to have lower temperatures than subalkaline magmas, and erupt from shallow, cool storage as viscous strombolian eruptions. However, many older, preserved, highly alkaline eruption sites are purely monogenetic. These may have erupted without shallow storage, in which case they could have erupted at high temperatures as direct mantle eruptions, with low viscosity.

Two historical volcano eruptions that had very hot alkaline magmas more than 1140 C are Hualalai and La Palma. Both of Hualalai 1800’s eruptions, produced very hot silica-poor alkaline basalt with 42% SiO2 and 1140 C. The 2021 basanite from la Palma has very low silica content combined with a very high temperature close to 1200 C. The viscosities in the latest geological reports of the deep basanite magmas from la Palma are incredibly low, as low as the very lowest viscosities from Nyiragongo and Hawaii, and lower than almost any historical magma. But Nyiragongo also has that combination of high temperatures and very low SiO2 content. Nyiragongo does have the record among frequently erupting silicate volcanoes as having the lowest SiO2 content, and Nyiragongo’s temperature is high enough to push the viscosity down to one of the lowest among any silicate magma. Nephelinites and basanites have the specs of having the lowest viscosity if they are combined with a high eruption temperatures. (Basanite is slightly less alkaline and little more SiO2 rich than Nyiragongo’s foidites). They are both very rare magmas.

Images: La Palmas 2021 eruption erupted ultrabasic lavas as well, a hot basanite. It was close to 1170 C and had a phenomenally low viscosity, one of the lowest ever seen in historical times, because of high temperatures combined with low SiO2. Its viscosity was in range of Nyiragongo
Images by: Instituto Geológico y Minero de España cropped from film https://www.youtube.com/watch?v=RxrCcmq4kGo

Conclusions and final thoughts about Nyiragongo’s viscosity

It is difficulty to know if Nyiragongo is the most fluid silicate based magma. While the silica content is very low, there are lots of other factors that determine viscosity, like temperature. Magmas are highly complex fluids that do not really have a single melting point.

Nyiragongo does have very low viscosity, one of the lowest measured viscosities of all silicate magmas on the planet. But there have not been enough studies on Nyiragongo on this question in my opinion. No volcanologists have been close to the erupting flank vents to measure viscosity.

The research that was done in the 2003-2021 summit lava lake is inconclusive. While very low in viscosity, it has not been lower than hot basaltic lakes in Hawaii. The extremely fluid-looking flows of near vents of 1977, 2002 and 2021 have a lot to do with very high eruption rates as well as with low viscosity. The volcano does have the lowest silicate content among terrestrial silicate lavas and it is the least polymerized lava at any given temperatures. But really hot basaltic lavas in Iceland and Hawaii can have the same low viscosity because of their very high temperatures. The fluid glassy watery look of the 2002 and 1977 near vent flows have a lot to do with that they where degassed and not frothy rather than being insanely runny, they where runny but perhaps not more so than other fluid lavas.

Nyiragongo does have the lowest amount of silica polymerization at any given temperature because of its very low silicate content, meaning that a normal basalt and nephelinite at same temperature, would have the nephelinitic melt as the most fluid. The magmas of this volcano also has remarkable mobility even at undercooled conditions (below full liquidus point) because of their low silica content.

Nyiragongo’s viscosity is low, but the myth that it is as fluid as water, is clearly just a myth. It is mainly created by the very fast eruptive rates of this volcano’s flank drain-outs that are one of the fastest effusive eruptions on Earth in terms of effusion rates. Its the steep slopes and fast eruption rates that creates the lava flow speeds together with a low viscosity, and many other fluid mafic lavas would also be just as dangerous if they erupted in the same conditions.

I have spent hours, hours on youtube videos and looking at photography comparing Nyiragongo with different fluid lavas mainly with Hawaii and mostly I cannot see any difference at all. Hawaii’s lavas appear a little hotter and brighter and much more shiny in cooled surfaces, but the viscosity looks just the same. The two lavas do look very different. Nyiragongo lacks the shiny aluminium looking skins of basaltic flows because its silica content is so low it does not form a nice glass up on air cooling. Nyiragongo lava lakes and lava rivers have a glossy look on its sun exposed surfaces, instead of Hawaii’s and Fagradalshraun’s shiny crusts. The lava lava lakes also look radically different, with Nyiragongo’s nephelinitic lake having numerous small degassing spattering points, and a strongly fissured glossy crust as normal convective regime, while Hawaiian basalt lakes haves a shiny aluminium looking crust with a few large plates and a few degassing points. This certainly has to do with Nyiragongo’s composition and different gas content. In some videos I seen of Kilauea’s summit lava lakes, it sometimes actually looked more fluid than Nyiragongo’s lava to my eyes. But this could also be because Hawaii’s lava is more “glassy”.

Nyiragongo’s lack of polymerization because its low silica makes it unable to form Pele’s hair. In other words, Nyiragongo’s composition is totally bizarre if you compare it to the basalt lava from Holuhraun or Hawaii. In theory Nyiragongo should be more fluid, with its much lower polymerization at any given temperatures, but Nyiragongo’s viscosity has a lot to do with temperature and how differentiated it is as well.

A very important thing when looking at Nyiragongo’s viscosity is that it is a well formed volcanic system and with a well built magma chamber storage, that allows Nyiragongo’s magmas to cool. The very slightly evolved nature of Nyiragongo’s nephelinites (not 100% fresh from mantle) maybe increases viscosity to the range of very fluid basaltic lavas. A monogenetic example of this magma composition could be even a bit more silica poor and primitive than Nyiragongo’s own nephelinites.

Temperatures are very good as well at removing that silicate polymerization, and thats why many normal basaltic lavas can be exceptionally fluid despite their higher SiO2 if they are hot enough.

But a truly primitive nephelinite / melilinite, like the extraordinary magmas of Vogelsberg, Urach that goes to below 30% Sio2, will be much more fluid than basalts, if they erupted at same temperatures as normal basalts.

But to end the discussion, Nyiragongo is almost certainly not more fluid than Halemaumau or Fagradalshraun’s basalts, that are both hotter and more silica rich than Nyiragongo’s. In other words the viscosity is probably the same (although Nyiragongo could be a bit lower in viscosity) but its impossible to say really. Nyiragongo’s nephelinite is one of the planets most fluid silicate magmas, but it is hard to say if it has a lower viscosity than a really hot basalt. The contest of which is the most fluid currently active silicate based magma/lava ends with a draw… and that ends this series.

Jacques Durieux with his lava sample pulled from the newborn lava lake. The 2003 samples from Nyiragongo were crystal free nephelinites at full liquid temperature so the rebirth of the lava lake came fresh from mantle. Such hot crystal free ultrabasic magma will have a very low viscosity.
Photograph by Patrick Aventurier during the 2003 sample expedition

Photographed by Patrick Aventurier during the 2003 sample expedition


This article series is mostly based on what I learnt myself about volcanism, Nyiragongo and lava rheology and is written in my own words which is the whole point, but some scientific sources that support my materials can be found below here.

Fledgling Mantle Plume May Be Cause Of African Volcano’s Unique Lava https://www.sciencedaily.com/releases/2009/03/090313110733.htm


Petrogenesis of Basanitic to Tholeiitic Volcanic Rocks from the Miocene Vogelsberg, Central Germany https://academic.oup.com/petrology/article/44/3/569/1576323


Thermo-rheological magma control on the impact of highly fluid lava flows at Mt. Nyiragongo https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2006GL028459

Dynamics of the Mount Nyiragongo lava lake https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013JB010895

January 2002 volcano-tectonic eruption of Nyiragongo volcano, Democratic Republic of Congo https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2006JB004762

Nyiragongo https://volcano.si.edu/volcano.cfm?vn=223030#bgvn_197203


The rheology of crystallizing basaltic lavas
from Nyiragongo and Nyamuragira volcanoes, D.R.C. http://jvolcanica.org › ojs › article › download

Jesper Sandberg, July 2022

261 thoughts on “Nyiragongo and its ultra alkaline magma – Part IV

  1. Thanks Jesper for the article. I think that the crust of lava flows may somewhat limit the viscosity of lava, particularly with ‘a’a flows. The ‘a’a flows of Nyiragongo as they reached Goma were very slow and easy to escape. When the lava has no crust, when it has an incandescent surface, it is probably when it behaves the most fluid. Close to the 1977 vents it would have been like this, a surge of glowing unrestrained nephelinite. ‘A’a seems to behave similarly regarless of being a nephelinite, a basalt, or a basaltic andesite, because the outside is solid.

    Personally I do think nephelinites, melilitites and basanites are always more fluid than basalts and that temperatures do not vary too much in between them, but there is certainly room for debate. Nephelinites and melilitites usually get blown to ash because of how much volatiles are in them, so you don’t get too see a stream of lava anyway. As such the degassed nephelinite of Nyiragongo is a rarity.

    What’s certain is that carbonatites are the most fluid lavas on Earth, and they do come from silicate magmas, it is simply part of a silicate magma (comprising carbon, sodium, potassium, calcium, fluorine and such) that has separated away and made something new.


    • Thank you … yes a really primitive Nephelinite/ Melilitite like the german stuff with well below 30% Sio2 .. will probaly be alot more fluid than say Fagradals and Kilaūea ..

      But Nyiragongo its more difficult to say with its sligthly evolved Nephelinite ( and most important) Nyiragongo seems to not be as hot as Thoelitic Basalts Because its an established chamber system. Althrough Nyiragongo remains as fluid as Halema’uma’u at lower temperatures thanks to its very low Sio2

      The contest of which is the most fluid currently active silicate based magma/lava ends with a draw… and that ended this series.. 🙂

      • True, it is a question that is very difficult to answer. I think mesuring the size of bubbles rising through a relatively uncrusted lava could be a good way to measure the real viscosity, so as to not need to many guesses on what is the temperature or the crystals. Doing that would be difficult though, but would give a definitive answer, maybe. Other features like standing waves, or differences in flow speed could also be useful in measuring viscosity. I’m sure it could be done with the necessary knowledge, software and data.

    • La Palma certainly did an incredible display of fluidity. Those textures have a beautiful smoothness I’ve never seen in Kilauea, could be the high quality drone footage though.


        • Fogo basanite also flows swiftly when not crusted. In comparison the a’a flows bear the appearance of a black slow glacier instead.

      • The lava channels in that video are not competely smooth If you examine the surface

        Althrough that coud be simply because Basanites are so low in Sio2 its unable To form a nice flexible glass

        But I seen many Photos of Kilaūea Looking very much smoother

        • Its a bit different too, Kilauea eruptions that make tube fed pahoehoe are lower effusion rate, Pu’u O’o average was 4 m3/s and that is the same for the eruption today. La Palma had a much higher effusion rate, an order of magnitude higher, which is probably why all the flows were a’a but also probably is part of why the flows were so fast. The fact it still formed tubes is actually quite fascinating.

      • But clearly very fluid .. even If its temperatures is lower than say Halema’uma’u

      • The lava lake looked hotter in 2003 than it Did in 2020
        Perhaps the stuff cooled in the shallow part Despite convection

    • The crust makes the viscosity hard to see but does not change it, unless the whole flow has become crusty. It does change the flow speed but that is a different issue. In more viscous fluid, the flow is near zero where it touches the sides (the bottom or if present, the crust) and is highest the furthest away from the sides. At low viscosity, much more of the fluid goes at full speed. At Leilani, the lava boats went much slower than the lava surface. That shows that deeper down the lava was moving slower (that is where the lava boats got their push) and indicates that a few km from the vent, the viscosity was not as low as water. The centre of a lava tube may be the best place to judge viscosity.

      • Here you haves how fluid the lavas are in Kilaueas summit lava lakes it is so extremely fluid it looks like liquid aluminium .. astonishing it is really! And addictive to watch

        With high temperatures the Sio2 content gets less important

        I think this is just as runny as Nyiragongo.. Althrough it loose its viscosity faster as it cools with Hawaiis higher Sio2


        11:01 – 11:11

        • It is interesting that tholeiites are super-shiny, but that has more to do with the composition than with the viscosity, I think.

        • Shiney because of sillica saturation

          But.. also very fluid because of high Temperatures

      • Yes, I should rephrase that. A’a flows are slower, thicker, with bigger wrinkles than fully molten lava of the same composition, to the point lava flows of naphelinite, basalt and basaltic andesite look and behave much the same. But the molten inside has the same viscosit.

    • One thing that seems to be clear when watching these videos is that basanites and nephelinites have much smaller crustal plates than tholeiite basalts, this applies both to lava lakes and lava channels . This could perhaps be explained by greater fluidity. It would be easy to measure the size of the lava plates as long as the width of the channel or lake are known.

      • Coud be .. but it coud also be that Hawaii and Icelands fluid Thoelitic Melts are better at forming a plastic flexible surface …with the Sio2 polymers.. resulting in less plates …

        Halema’uma’u can have tiny tiny plates If the lava lake is disturbed by a rockfall

  2. Should me add my name at the ending of this article ? : ) the Author needs to be seen ; )

  3. Thank you Jesper!
    A thoroughly scholarly series. Very well written and very informative! Really impressive work.

    • Thank you .. yes was well needed seriers because its a lack of information on Nyiragongo on the internet

  4. 2022-07-31 17:48:01.3
    14min ago
    63.89 N 22.20 W 8 5.0 ICELAND REGION

    Not verified by sismologist yet…

    31.07.2022 17:48:50 63.870 -22.350 1.1 km 5.2 50.5 5.2 km SW of Fagradalsfjall

      • Location seems confused. It does not look to be at Fagradalsfjall itself as the signal is a bit smeared out. The automatic positioning puts in the sea north of the peninsula which seems unlikely? I am wondering whether it is closer to Grindavik. Just a guess

        • This might be unreliable, but I looked on the VolcanDiscovery app and the 5.2 is at Grindavik and a 5.0 near the Krísuvík system. However, I do notice a small swarm at the eastern part of Krísuvik. I could be wrong here, but something is going on.

          • IMO has now reviewed it. It is listed as an M5.5(!) and just 1 km east-northeast from Grindavik. 2 km depth. I expect it is on the Reykjanes fault (zone)

          • It is strong enough that there could be damage in the town ?

          • Also near Grindavik, from the same app, another 5.2 a bit more northeast from the one closer to Grindavik.

        • Spot on Albert.
          31.07.2022 17:47:59 63.851 -22.389 1.9 km 5.5 99.0 3.0 km ENE of Grindavík

          Highpass Grindavik shows it (plus aftershocks) well.

          I can’t get used to the faf station, the signals are always a bit smallish compared to other stations. I wish IMO could adjust the signals of the all stations to a standard.

          Credits graph IMO.Rob

          • Huge tail low hertz grindavik plot! Brrrrrrrrrrrrrrmmmmmm.
            How would that have sounded like…

            Credits graph IMO

  5. It was a good shake on the mbl.is webcam, maybe 3-4 seconds. Above 6100 on the alert map.

  6. The level of blue smoke has interesting on the Webcam.

  7. Much compliments on your articles Jesper. It is quite a read! Admiring your effort, labor on it! Thanks.

    I am struggling on a piece about spherulites in rhyolite some years (😓) now. I guess I must finish it this year, when not, it will stay somewhere in a dungeon forever.

    • Thank you .. yes it was needed .. it Answers a few questions that many persons have about Nyiragongo

  8. Frettir from IMO on Reykjanes unrest, updated 31.07.2022 kl 15:27, google translated:

    “”The earthquake series that began at noon yesterday northeast of Fagradalsfjall continues, but a total of almost 3,000 earthquakes have been detected by the Norwegian Meteorological Agency’s automatic location system since the series began. Of these, there are four earthquakes above magnitude 4. The earthquakes were first at a depth of about 6-8 km, but since 6 pm last night, the seismic activity has deepened and remained stable at a depth of about 2-5 km. The attached photo shows how the unrest started to increase around 12:30 yesterday.

    The magma intrusion at Fagradalsfjall causes voltage changes northeast of Grindavík and west of Kleifarvatn and causes earthquakes there. These earthquakes are often called trigger earthquakes. Since the earthquakes at Kleifarvatn are closer to the capital area, they can be clearly felt there despite being slightly smaller in size. The attached map shows the locations of the earthquakes since the start of the storm.

    GPS data shows deformation at stations in the immediate vicinity of the activity. The deformation is consistent with a magma vent forming. This scenario is very similar to the activity in December 2021, but does not seem to be quite as powerful. The area will continue to be closely monitored.””

    Some figures included on https://www.vedur.is/um-vi/frettir/jardskjalftahrina-a-reykjanesi

  9. Not sure, but material falling on the vulcano camera?

  10. Stupid questions do not exist, I was told on more than one occasion and maybe this one was discussed before but:
    I like lab experiments. Nice and controlled and such. So couldn’t you take lumps of (fresh) lava. Melt it, mix it (in case of phase separation) and just measure the viscosity? Possibly at different temperatures?

    • Thanks: Right Althrough I have not found much information on souch experiments …. perhaps they are very difficult and expensive to do and fiddly. First the lava haves to melted in a furnace.. thats a bulky and slow process.. then comes the fiddly process of measurements of viscosity

      Melting lava should be quite easy in an efficent furnace, Althrough lavas low heat conductivity and huge heat capacity makes it an energy expensive process ( see the university of syracuse lava pour experiments)

      But yes They should melt ”normal” oceanic basalt in one furnace, and melt Nyiragongos and The german Nephelinites in other furnaces and compare the behaviour of the lava

      The german Vogelsberg and Urach Nephelinite and Melilitite lavas are insane as Sio2 based ones with Sio2 well below 30% for them

    • I don’t know the full answer to this. The samples that are taken are mainly used for determining the lava composition. The elements and minerals can tell where (and perhaps how) the magma formed. There is probably less interest in measuring viscosity as it tells us less, and of course depends very much on temperature which changes rapidly with distance from the eruption. You need to reheat the sample to the original temperature, not easily done or even known. The temperature history may also play a role: crystallization (and melting) takes time, so it makes a difference how quickly the sample is reheated. And crystals drop out of the melt, so you need to ensure the sample is not just taken from one level in the lava. So – not easy and perhaps not worth the effort.

      • There been a few measurements of viscosity for Both Kilaūea and Nyiragongo in souch and other experiments, I read a few earlier .. all is inconclusive.. but both volcanoes can display amazingly low viscosity

        Almost No experiments have Involved melting down ultrabasic lavas like Nyiragongo

        ( here is videos of very fluid behavior of the 2008 – 2018 Halema’uma’u lava lake )



  11. Here are the latest (preliminary) quakes, now including the big one. Note that the clustering is somewhat arbitrary, just trying to distinguish locations in a sensible way.

        • Quakes are clustered into groups according to their geographical distance. The number of clusters as well as the clustering method is (more or less) carefully chosen by the author (me).

  12. There was (very) weak tremor at fragradalsfjall an hour ago

    • Albert, what time UTC or Iceland, did that occur? I would like to take a look, and what seismographs did you look at?

  13. Quite a lot of blue haze coming from the crater now on the close-up cam. But it might be heading in the direction of the camera making it look worse?

  14. There seems to be more quakes that are under 2 km deep now than before. Still by far the majority are deeper but then if quakes mostly happen under the dike this makes sense. The dike is also not going along the rift, and seismicity is still holding, I think we might get an eruption out of this one 🙂

    Also looks like a line of quakes north of Grindavik. It is most likely an aftershock sequence but it is also in the same place that got a lot of quakes earlier in the year when magma was intruding, so could still be something to look out for. I dont think any of the different fissure swarms erupted simultaneously in the last Reykjanes fires but then Fagradalsfjall was not a thing then either so who knows…

  15. Bravo !!
    Wondrous, enlightening, thought-provoking series of articles…

    A couple of thoughts:
    Is the ‘alkaline’ source just separated components, or is there a subducted salt-bed in the mix ? The Vesuvian could be fairly recent geologically, from the former Tethys, via some mini-Messinian cut-off. But the African supply may be truly ancient as, IIRC, its cratons have been together for a long, long time. When could they have over-ridden the makings ??

    Are these alkaline lavas thixotropic ? Such they run better when fast than slow ??
    ( Per snow avalanches and mud that flow like water, set solid when they halt….)

    Short of a full-on Plinian or Mt St Helens ‘lateral blast’, I’d have said a big ‘nuée ardente’ pyroclastic flow ranked high for ‘Be NOT There’. Seems a perched lava lake spilled down a steep cone trumps such…

    Been a life-time but, in passing, I used to test purchasing samples and deliveries of tablet-coating lacquer. This was the ‘natural’ stuff, derived from actual waxy bug-wings, and could be notoriously variable. Nay, fickle. Literally depended on the bugs’ diet. You know how fatty poultry may keep a taint of fish-meal if not switched soon enough ? Sure, we tested for contaminants such as salts and oils, but viscosity was key. IIRC, we’d dip a clean, dry microscope slide into a small beaker of the stuff, clamp it to drip back into the beaker. We’d time how long it took to drain to a uniform thin film, log the room temperature, to be sure. Sometimes, the lacquer clung like gear-grease, some-times it ran off like pi$$. Neither could be used. Surface tension was important, too. Sometimes the stuff drained smoothly, but beaded at the drip-edge. That would ‘play hob’ with the coating process, was a ‘reject’…

    • Usually the alkaline is somewhat of a partitioned melt that is selective, tends to take more of certain elements, leave more of others.

      But the composition of the mantle also matters, and in particular with Italy’s case. After seeing many TAS diagrams, isotopic data, and element data I have become increasingly convinced that the composition of the mantle under the Italian forearc is a trachybasalt or similar. A very unusual potassium rich mantle. Volcanoes like Etna, Stromboli, or Campi Flegrei would be tapping directly this chemistry. Vesuvius, Vulture, and Colli Albani would be extracting more alkalic phonotephrites from the trachybasalt mantle. I do think the subduction zone is adding some material to the Mantle that shifts its chemistry. The Italian chemistries are very unusual, you can see that when you plot volcanoes like Vesuvius or Etna in a TAS and compare them to elsewhere in the world, the distribution of data points its very unique, their fractionation series start from very high potassium compositions, each volcano covers a remarkably large section of the TAS, and they climb very steeply in the TAS as they evolve. It is as far as I know rather unique.

      The opposite would be Iceland, with an extremely potassium depleted mantle. The alkaline volcanoes of Iceland, like Hekla or Katla, are subalkaline/tholeiitic in a TAS, which is a classification used for the whole world that doesn’t include regional differences.

    • Nyiragongos magmas are produced from very small ammounts of partial melting in a carbonated metasomatized mantle, its also produced very deep down under high pressures, well below the partial melting of basalt. Magmas like Melilitites and Nephelinite probaly haves their origin 150 to 200 kilometers down, perhaps even deeper. Making Ultrabasic Alkaline magmas the deepest magmas on Earth, its alkalinity haves to do with a very small ammounts of the whole mantle composition goes into the magmatic melt during formation

      The red flames from Nyiragongos degassing cooling flows haves to do with its high alkalinity, rich in sodium and potassium

  16. Monday
    01.08.2022 08:02:33 63.913 -22.013 5.5 km 4.1 99.0 3.8 km NE of Krýsuvík

    01.08.2022 06:27:34 63.916 -22.226 3.8 km 4.7 99.0 2.8 km ENE of Fagradalsfjall

  17. ”This is the most fluid lava anyone has seen in the world,” says Asish Basu, professor of earth science at the University of Rochester”

    Hahaha that statement is very questionable about Nyiragongo.. I nailed him

    But never say never.. in some Photos like in 2002 and some Kraffts 1973 videos of Nyiragongos lava lakes like this one: 22:54 – 23:32 it does look extremely fluid https://www.dailymotion.com/video/x6e99md

    At 23:27 it does look more fluid than almost any other basalt, and Hector is right that the degassing is very small .. Althrough Hawaii can have small bubbles as well along lava lakes edges.

    So its not a finished contest yet who is the most fluid currently active sillicate lava ( Nyiragongo coud be ) But difficult to say

    But of all Possible lavas on Earth its the Komatites, Kimberlites, and truley primitive Melilitites and Nephelinites ( german alkaline lavas with Sio2 at 25% ) They will be much more fluid than Nyiragongo and Kilaūea

    • I would say that the hottest lava erupted from Kilauea probably is a little more fluid, high temperature really does make a big difference in magma. But not all lava erupted by Kilauea is the same, and ERZ lava is probably a bit more viscous, it is certainly not as hot unless it is erupted right out of the connector (1968, 1973) which is pretty rare. So Nyiragongo probably is more fluid than the lava from Pu’u O’o, or what erupted in 2018. In all these cases though it is very close, all of the really fluid magma is probably within the same order of magnitude, even when there is a lot of crystals in it like at Etna the melt is very fluid, as you say it is a bit like ice-water or wet sand.

      The lava at La Palma generally seems to be not too far away from these two either and like Nyiragongo its speed might be in large part due to erupting directly onto a steep slope (something that is rather rare in Hawaii or Iceland unless a caldera is in the vicinity), but there is one video that shows lava fountaining from a vent and flowing down the cone, and in doing so it forms repeated hydraulic jumps that are only formed by fluids of extremely low viscosity flowing down a slope. This is easy to see if you flow water down a slope in a flat sheet, but in lava flows I have only seen a similar phenomenon before on a video of Mauna Ulu, where lava flowed down the steep slope to the south. Apart from that, however, I have never seen anything like it otherwise in other volcanoes, so it could well be that the 2021 la Palma lavas are the record holder. I dont know if that can apply to Cumbre Vieja as a whole though, some older flows look much more viscous, but these could also be secondary collapsed cone spatter flows and as such not representative of the original magma.

      • Enjoy these
        Found same fluidal features at Nyiragongo as in La Palma

        But it does seem that all hot lavas .. with low to medium Sio2 as you say Will have a very low viscosity

    • Thank you for posting that David Attenborough video, Jesper. For the past ages, I’ve been wanting to walk through cooled lava tubes but seeing all those pigmentary-challenged insects in close up have ruined it for me. I’m not quite so eager now. 😂 Seriously though, great video.

      • Its his program althrough the Nyiragongo volcano footage is from 1973 from the Kraffts

        Attenborough is amazing and he Is soon 100 years old and he seems to be in good health. Because He have luckly avoided both dementia and heart disease, Probaly because his sugar intake was low, through his life, since sugar is very inflammatory

        He will be producing more series soon and many of his past seriers are my favorites.
        A Perfect Planet had one episode with him .. explaning the relationship with animal life and active volcanoes

        2001 s episode 2 of the Blue Planet ”The Deep” is an Attenborough legend and won many awards and its one of my favorite works of Attenborough: you can see it here https://watchdocumentaries.com/the-blue-planet/?video_index=1

  18. ?w=778&ssl=1

    The figures for the German alkaline lavas are totaly insane! That Hector provided .. some of these Melilitites and Nephelinite are almost down at 20% Sio2 .. with Ingwisi Hills Kimberlite even much lower. I never knew before that sillicate magmas coud get that Sio2 poor

    If these lavas erupted at basaltic temperatures then they will be much much more fluid than a basalt .. perhaps almost like Lengai but glowing hot in daylight .. being a sillicate magma

    • Being realistic, if the Igwisi kimberlite is only about 12-13% SiO2, is that even properly called a silicate magma anymore? I havent looked into specifics but I would expect some other components would be in a greater proportion. Carbonatite as I understand it is basically igneous calcite or limestone, carbonates of Na, K, Mg and Ca, and the silica content pretty much has to be nearly absent for it to fit into the classification. I think kimberlite has got a high percentage of carbonate too just more than negligible silicate content. Im not sure if there is more CO2 vs SiO2.

    • The Urach Melilitites/ Nephelinite at 22% Sio2 .. sourely woud have been insanely fluid If it was same temperatures as basalt eruption but its possible that the high carbonate content lowers the melting point and eruption temperatures as well

    • A Kimberlite at 5% Sio2 is indeed hardly a sillicate rock .. thats astonishingly Sio2 poor

  19. Hi Folks, currently watching the seismic activity in Iceland.

    Could I ask someone to do a summary piece of what we know so far, Dike size, location, propogation and speed. Eruption possibility and so on.

    Currently browsing flights from Dublin to Iceland!

    Mise le mheas


    • Though activity is quite strong, there’s no mention specifically of magma on the move nor if an eruption is imminent. ATTM, the widespread foci of the stronger shocks would suggest this latest swarm is mostly tectonic, but with magma so close to the surface, if a crack opens up then things could rapidly change.
      From IMO a few hours ago:
      “Since midnight 1st Aug several events of M>=4 have occurred. At 3:14, an earthquake of magnitude M4.3 was detected about 4 km SSW of Fagradalsfjall. At 3:41 an earthquake of M4.2 was detected about 4 km N of Grindavík. At 4:51 an earthquake of M4.4 occurred around 3.3 km NW of Grindavík. At 08:02 a M4 occured at southwestern Kleifarvatn.
      At 17:48 yesterday, an earthquake of magnitude M5.4 occurred about 3km ENE of Grindavík. It was felt east to Fljótshlíð and west to Snæfellsnes.

      A strong seismic swarm is ongoing just northeast of Fagradalsfjall, and trigger earthquakes are occurring east and west of Fagradalsfjall. The activity started around noon yesterday and since then around 5,500 earthquakes have been recorded on the IMO’s automatic system.
      Increased risk of rockfall is in Reykjanesskagi and has been reported in the area. People are advised to be careful on steep slopes, near sea cliffs and avoid areas where rocks can fall.

      • Actually, IMO have said magma is moving to cause this. The quakes at Grindavik at least this time around are tectonic and caused by strain from the dike near Fagradalsfjall. It is though something to consider the sequential intrusions near Grindavik, those are sills not dikes, I dont consider them as failed eruptions but as magma accumulating and a fault moving that intersects could well initiate another dike and eruption there.

    • It might be an illusion, but the depth chart appears to show a kind of layer at 1km depth. I wonder what causes that?

      • 1.1km is the default depth for quakes that could not be fitted automatically. Those are best left out

        • Right. At one point I had that in the code, but I removed it (couldn’t remember why). I’ll delete these quakes …

        • I also found a small bug in the code. This is so embarrassing…

          • Proper programmers always have bugs in their code, the difference is they spot and fix them.
            Personal experience.

          • Wait until you make a bad post to all the number theory mathematicians in the world (numbertheory listserver NODAK), then have to apologize.. really red-faced over that one.. I understand your post 100%

  20. Is it super windy or are the webcams all shaking from the constant earthquakes?

  21. The swarm seems to be abating – perhaps temporarily. Quite a long section of the Reykjanes fault has been activated. The main intrusion seems to be between Fagradalsfjal and (east of) Keilir but the largest quakes were on the main fault near Grindavik, presumably already primed after the earlier intrusion there. There is little sign of inflation (Grindavik shows deflation) but several GPSs moved quite a bit: krysuvik to the southeast and fargradalsfjal south.

    • It seems to have “unabated” since your words. It’s listening to you!
      The quakes close to Grindavik unnerved me a bit, for they reminded me of Carl’s prediction of north-east of the town being a likely eruption point.

      • Oh why can’t I type and think. North by northWEST of the town. No Cary Grant required…
        (Is that a biplane on the webcam?)

        • Clivwe, you certainly mean the quakes close to Mt. Thornhill?

          • Þorbjörn, near the Steam Plant. I believe Carl had a theory the intrusion could break surface immediately south of Þorbjörn. I hope he is wrong.

          • Clive, Mr.Þornhill (also known as Mr. Kaplan) is the guy from the movie. I thought I was witty…

      • I love the word “unabated” Clice. I agree, I think perhaps the earth was just taking a breather from it’s ‘birth pangs’. Currently most definitely going through another spasm.

          • Albert as long as no one is a reprobate then they totally deserve a rebate. 😉

          • And…. Haha, you totally sound like my twin brother whis is probable around the same age.

    • Following the GPS 400 days graph, all stations seem to move in the same direction as the intrusion in december 2021. One exception GONH. It is moving northeast together with FEFC and GRIC (south in the area). In 2021 GONH was moving southwest together with FAFC.
      In 21 and also now GONH is deflating.

      I don’t know the exact location of GONH, but it is about inbetween FEFC and FAFC, possibly at the west side of the Geldingadalir Valley (the valley that got the lava first during the eruption)? Anyone?

      Curious about the deformation (Insar) of the area and where the intrusion shows uplift most.


      • GONH = Gónhóll = Theatre hill. The hill closest to the cone where visitors went before the path was cut off by lava.

  22. The swarm seems to be slowing somewhat, it is not as intense as yesterday. I wonder if that means magma has done all the rock breaking it needs to and now will definitively push up and erupt? Last year it took a month but now it might not be nearly so long if a lot of the strain is already released. And then last year it also erupted after a quiet time, maybe the rift opens basically all the way up and the magma simply fills up slowly, in this case the short length of the dike might favor an eruption more than that in December.

  23. Another candidate for the most fluid frequently erupting sillicate lava, coud be the Thoelitic Basalts that emerge from Superfast Spreading Ridges, because there very hot mantle is very close to Earths surface, just a kilometer or two for the very fastest ridges, basicaly fresh mantle melt directly out in the seafloor. Mantle is very hot in fast spreaders, Althrough Hawaii is a way much hotter mantle still

    Still lavas at Superfast Spreaders may erupt commonly at 1240 to over 1300 C simply because the litosphere does not exist and crust almost does not exist either at souch Superfast ridges. Souch lavas will have a very low viscosity. Superfast Spreaders are insanely thermaly active with black smokers all along them with seawater very close to the hot magma. A majority of Earths volcanic heat release comes from fast ridges with their very thin crust

    Eruptions along Superfast Spreaders can be spectacular with very high eruption rates, similar to Mauna Loa and Galapagos eruptions
    Souch fast submarine eruptions forms ”Sheet Lavas” the lava flow output is so fast that the lavas flow just like on land. Lava channels and lava vortexes are common on Superfast ridges infact the seawater hardly cools the lava at all at souch eruption rates, the thin glass crust is good insulation. Sheet Lavas are common on Fast Ridges, since eruptions are too fast for pillow lavas. Pillow are more a thing of slow ridges. Some submarine sheet flows are real lava floods just like on land, and acually the crust on souch sheet flows forms vortexes and flow lines .. signs of fast eruption rates and a flexible crust. Submarine sheet flows will still mostly have a dark apparence when it erupts because of water cooling: But it flows like on land very much just as quickly. That glass crust is great insulating.. from the sea and lava stalatites are common on the underside of souch submarine lava crusts, showing how good it is at retaining heat. It coud flow faster than you can runn in some cases over the seafloor

    I have dreamt awsome vivid Sci Fi dreams of eruptions along Superfast Spreaders, with Sci-fi submarine mining bases ( They are mining the hydrothermal vents for metals ) with human figures in bioshock like suits mining and submarine bases capable of standing the pressures. In one dream the ridge blew .. and thousands of personal escapes the hellflood in their pods to the surface. Whole bases on the seafloor are buried by lava tsunami.

    A thing almost similar in real life to that stuff happens When the deep Sea hydrothermal vent ecosystems gets destroyed by the lava flows and the poor vent animals haves to find another black smoker to feed on.. also black smokers can just turn off as well

    • Imagines a deep Sea hydrothermal vent system pile becomming an Island in a raging flood of lava .. the lava boiling the tube worms, crabs, and the odd white eel fish flee for their lives..

      The heavy lava may just topple the hydrothermal vent system thats just a pile brittle metal oxides sand like dust…

      Surreal sight

    • Quite Spectacular Sci-fi dreams about the EPR. Althrough I wish I was better at painting, so I coud show you what I acually dreamt. Totaly wild acually with their submarine rovers floating in the river of liquid rock, but in real life souch equipment woud be crushed to a pulp by water pressure

      Almost 20 centimeter faster than Iceland are some of these spreading ridges .. in the pacific and thats enough to make the morphology very diffrent from the Atlantic Ridge

      But Iceland is a unique ridge as well
      A ridge massivly boosted by a Mantle Plume

      • But the 4000 C liquid stuff that Chad talked sounds even more terrible ..than liquid titanium a liquid combustion reaction as hot as a stars surface .. No vat woud be able to hold souch a liquid unless cooled by liquid hydrogen in same way as rocket engines

    • But the hottest possible erupting lava is Hawaii Hotspot with deep eruptions of 1700 C possible and as fluid as liquid iron at souch temperatures.. Looking like a flood of liquid iron or even liquid sunlight: lava as hot as liquid titanium

      Anyway there must be nothing more scary than liquid steel or liquid titanium with its high density and it conductivity towards the body: really terrible stuff ..

      But the most fluid frequently erupting lavas are perhaps the basalts from Superfast Spreaders

      • Liquid titanium would burn on contact with air, probably very agressively as it also burns in nitrogen which is what stops most other metals burning in our atmosphere. It doesnt easily ignite as a solid so is generally safe but powder or liquid is extremely flammable.

        I think some steel formulations also will ignite if exposed to the stmosphere for long enough as a liquid, certainly iron will burn very agressively in oxygen. It does make you consider thermite, which is extremey energetic even in spite of having to reverse the combustion of iron which is itself a very exothermic reaction, it is because aluminium has a low melting point and doesnt burn in nitrogen that stops it burning, as well as its oxide strongly sticking to the metal.

        • The oxidizer in a thermite reaction is the powdered rust. The powdered Aluminum is the reactant. Since it is a highly exothermic reaction, the newly liberated iron is in a liquid state.

          As far as I know, Thermite is only used for certain specialized applications, such as welding subway rails together.

          I have no idea if there is a way for controlling the carbon content of such a procedure. I would imagine that including the carbon in the mix would not provide a way of controlling how it diffuses into the metal. With the temperatures involved, I imagine the molten iron would just make any available carbon ignite and assist in consuming the available oxygen as it is freed up from the rust…. but that may tend to quench the reaction.

          • That is what I mean, the oxidisation of iron is very exothermic, so it takes a lot of energy to turn iron oxide back into iron metal. The fact that aluminium is able to react with it so violently and with so much energy that it not only reduces the metal but adds so much more energy to the system it leaves it at close to its boiling point, that is what I am talking about.

            From what I can tell the only metal that might be better at this oxide reduction reaction than aluminium is beryllium, even the alkali metals are not as energetic. Beryllium and oxygen reacting gives the most energy possible from combining two atoms, even more than fluorine reacting with hydrogen or lithium. In terms of what element has the highest oxygen affinity though, aluminium is the highest among common elements. If you mix Al powder and solid NaOH it burns (albeit slowly) with emission of dense orange flames from the sodium and hydrogen produced evaporating and burning in the air.

        • Most metals are reactive enough to burn in air and only do not do so by a coating of oxide which is often very tough, forms instantly and prevents oxygen reaching the metal. Iron is a plague because with water it produces a porous hydroxide so it rusts. Others do too, but less effectively.
          Try lighting steel wool as an example of burning iron.
          Most metallurgical applications cover the metal in slag to prevent oxidation, or just accept some surface losses.
          Titanium is interesting, has to be made and formed under vacuum because trace amounts of nitrogen will render it very brittle. Very very brittle indeed.

          • I have seen that titanium can be forged and worked pretty easily in open air if it is solid, it is more not really any more reactive than steel until it almost melts, but the way it is made leaves it initially as a porous spongy material and that has to be handled under argon. I think vacuum is when to has to be welded into very accurate shapes in small scales.

          • Chad, agreed.
            Forging implies hot, and that can allow nitrogen to be absorbed and diffuse into the bulk. Generally Ti is used for critical situations.
            Very happy with argon though.
            I once was lucky enough to come across some N-embrittled 12mm titanium bolts (originally for a nuclear sub I think) and was allowed to snap one with my bare hands. Scary.

    • Buried seismometers in jumbled sheet flow on the EPR

    • Nice Photos showing how quickly and fluidly lava can flow underwater, lava have very low heat conductivity and high heat capacity, so it keeps it heat very well underwater, the insulating glass crust is good at keeping the flows hot. Lava flows can flow many many kilometers underwater as long as the supply is going. These are called ”sheet flows” and are fast submarine flows feed by large Fissure eruptions. The crust is keept thin and flexible by a high lava flow rate

  24. CIVISA raises the volcanic scientific alert level for V2 of the Santa Bárbara volcano on Terceira island.
    Information had already been advanced by @Wessel in another thread.
    According to CIVISA, there was a waxing in the microseismicity in the volcanic system.
    No further information was provided on depths or hourly frequencies and magnitudes.

  25. Today (22:55 pm UTC 1-Aug-2022) the webcam https://www.youtube.com/watch?v=GCa4EMcWuoI shows intermittant sulfur dioxide from the Geldingadalir Fissure cone. To me, it seemed as if the emission of vapors decreased after the 5.4 quake. The amount of people watching the monitor has varied from 989 to 273 right now, so people are interested to see if this cone get reactivated.

  26. There are now quite some quakes under 2 km depth in the area of the dike, even at 1.5 km it is rcognisable. A day ago it was about 1 km deeper before the swarm started showing and most of it was somewhat deeper than that. I think the chance of an eruption here is quite likely, and if it keeos up the current rate it will probably be within the next 2 days.

    I think it might ebd up being maybe more powerful than the start of last year, maybe going similar to the last eruption peak but it starts off that way. I dont see it being much of a threat to the highway though unless it really goes crazy or it forms tube fed pahoehoe, neither case is particularlylikely if historical evidence is used but maybe shouldnt be discounted either.

    • https://skjalftalisa.vedur.is/#/page/map shows the manually checked quakes, but 559 quakes is a lot over quite a large area, along the rift, it seems? Just checked now (8:24 pm PDT) and the quakes picked back up again with one almost mag 5 at 02:27:04 Iceland time, a 4.5 occurred shortly thereafter.

      • They cover quite a big area of the peninsular though.
        Also love the new display with zoom etc.

      • 559 earthquakes may not be only the Peninsula; it may be the whole of Iceland.

        Number of earthquakes for the whole of Iceland from 29/07/2022 0:00 to now 412

        Number of earthquakes for the Peninsula from 29/07/2022 0:00 to now, 412


        • You have to choose an area using the ‘Svæði’ selection. Just zooming in is not enough. Select Reykjanesskagi to get the peninsula, or use to draw an area on the map.

  27. The M5 this morning is still producing aftershocks. It was on the ridge west of that big lake (Kleifarvatn), continuing the pattern that the quakes are on ancient (solid) fissures. Most of the Reykjanes peninsula is now taking part in the fun. Only the western and eastern edge are being ignored and probably resentful by now. There is a nice pattern to the quakes, with swarms 0.5 degree (20 km) apart. That could suggest that the ultimate source of the pressure that is breaking things is 10 km deep.

    • Here are the latest quakes from the Icelandic met office page:

      Hope my code is now correct (quake sizes were wrongly attributed to the right depths or vice versa). Otherwise I gonna need a bigger paper bag (r.i.p. Chief Brody).

    • Comment by Freysteinn Sigmundsson on the Insar via ruv.is

      Google translated
      “”Magma movements are clearly visible on a new satellite image and are now northeast of last year’s eruption centers, between Fagradalsfjall and Keilis.
      Six earthquakes above four have occurred in this area in the past 24 hours, the largest being a magnitude five.

      Freysteinn Sigmundsson, a geophysicist, says the images show that by far the largest deformation on the Reykjanes peninsula over the shopping weekend is caused by this magmatic intrusion.

      “We see that there is about sixteen centimeters of displacement. It is primarily the magma intrusion that creates this signal, but there are also other signals,” says Freysteinn.

      He says that there are clearly visible traces of the big earthquakes on Sunday. Taking into account the meeting of the scientific council today, it is possible to assess the inflow rate of the magma and it is important to monitor how it develops.

      You can listen to the interview with Freystein in its entirety above.””

      • Forgot to mention Sigmundsson works at Institute of Earth Sciences, University of Iceland.

  28. Grimsvotn is deciding to join in.
    02.08.2022 14:24:33 64.426 -17.243 1.4 km 3.7 99.0 2.7 km NNE of Grímsfjall

    • That’s significant for Grímsvötn. Could be interesting times ahead.

      • Alert level changed.

        Today August 2nd 2022 the colour code for Grímsvötn was changed to yellow due to several M>1 events detected this afternoon, largest event Mw 3,6 at 14:24 UTC. This means that seismicity by the volcano is above normal activity which calls for increased monitoring of the area.

    • Looks like there was a Mag 4.7 / 1.1 km (0.7 mi) depth 19.5 Km ESE of Laki too.

      • Given the quality of 50%, it is most likely either mislocated or the magnitude will be manually corrected.

      • Mind you it does say the quality is low so that one might be wrong, on IMO it’s 50.5%.

      • It’s a false detection caused by the waves from the M4.8 in Krýsuvík half a minute earlier.

  29. The camera operator zoomed in on some smoke. No idea yet what it is.
    mbl camera – various views

  30. Are we getting harmonic tremor on the fag and fal drumplots?

  31. Ooo this is exciting.
    I think Grimsvotn may pop first, it was thought likely after the Jokulhlaup earlier in the year and it’s been a hot summer.
    I might be misremembering but i’m sure Albert said April 2022.

    • That places the close up cam on Gónhóll – Theatre hill. Next to the GONH GPS.

      The smoking area is not a good spot for an eruption. If lava flows over the edge, there’s not much in the way to contain it. It would be more or less free to flow to the coast and in the long run it might threaten Grindavík.

      • That’s beyond Fagradals Crater. It’s the hill called (I think) Langholl.
        But it could be a grass/turf fire?

      • The hill is Fagradalsfjall, the smoke at the top of the eastern slope overlooking the lava field.
        So far as I can tell…!
        But lack of tremor makes me wonder if it is a vegetation fire.

        • I think you are right. It looks like the mossfires burning on the slopes there during the last eruption. They just went on for days, slowly creeping forward.

  32. Couple of people are investigating the smoke. I guess we’ll know before long what it is.

    • It’ll be interesting to discover what might have caused the smoke.

      2 thoughts: 1) This isn’t where we’d expect the ground to be heating up at the moment.

      2) The difference from the mossfires at the last eruption is that, I think, the consensus was that they were caused by lava bombs (I use the term loosely) igniting the moss. I haven’t been closely following the weather this summer in Iceland, but I think it’s been wetter and cooler than usual, and I am not sure that scrub fires are a normal feature of Icelandic hills in any case. Perhaps it was a stray BBQ ;(

      • I agree. It isn’t where we would expect the action to be. My bet would be that an eruption would start somewhere between Meradalahnúkar and Kistufell and maybe a few hundred meters to the west of that. That’s where the dyke is centered anyway.

      • It is hard for magma to start a fire without an eruption. Steamy but damp hydrothermal activity is possible, of course. Fire could start from a rockfall or from human intervention.

  33. From RUV.is. Translated using Google.

    If there is an eruption in the area between Fagradalsfjall and Keilis, it could be more powerful than last year’s eruption at Fagradalsfjall. This is what geophysicist Freysteinn Sigmundsson says. The flow of magma corresponds to ten times the flow of Elliða River. Lava could manage to flow to the north from the place that is considered most likely to erupt now.

    “It is most likely that it will be over this magma tunnel that is forming in the earth’s crust. And it actually extends from the eruption stations from last year and three kilometers in the direction of Keili, so that area is the most likely,” says Freysteinn.

    Freysteinn says that it is likely that an eruption at this location can reach Reykjanesbraut. However, it is not at all certain that it will erupt in the next few days. The reason for this warning by scientists now is this huge influx. “There is a higher inflow rate and that is the reason for this warning.” This corresponds to about 50 million cubic meters, which is the most likely figure that comes from model calculations by the scientists of the Icelandic Meteorological Office. It is ten times the average flow of Elliða River for comparison. But it is flowing into the earth’s crust and because the flow is greater, there could be more force in this eruption, but the nature of the eruption would most likely be the same, a lava eruption with craters and that the flow would be limited to certain craters, but there could be more coming up from them and then more gas could come out and possibly a little bit of pyroxene”, says Freysteinn.

  34. Interestingly, the last 3+mg quakes (99% verified) were 2-3km SSW of Keilir, which kind of puts them close to this area.
    Quake intensity is also abating (sorry Albert). Perhaps the intrusion has started degassing into the water table and generating some steam.
    If this speculative rubbish is any where near close to reality, it’s not beyond the bounds of possibility the intrusion may surface in this smoky area.

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