Making a shield volcano

Looking back to when Fagradalsfjall eruption started, I wrote a post about the Reykjanes Fires, where I speculated about how the eruption could end up being like. I mentioned two main possibilities. One was that it would turn out similar to the eruptions of the Brennisteinsfjöll volcanic system that took place 1000 years ago. The other was that the eruption would become a shield volcano, a dyngja. It has become increasingly clear to me that the current eruption is walking down the second path. A shield volcano in the making.

To watch the birth and evolution of a new volcano is a rare opportunity. I find it quite interesting. This is why even after writing three posts about the Fagradalsfjall eruption I still have so many questions and so much to say about them. This post will go about shield volcanoes and their varied types of activity, these I have divided into three “stages”, a simplification of the complex evolution of these volcanoes. I should say that by shield volcano I will be referring to those that are formed in one unique eruption, the term monogenetic is used in such cases. The contrary would be polygenetic, which are the volcanoes that go through many eruptions and long dormancies, so that they remain active for thousands or millions of years.

Why is Fagradalsfajall so different?

The first sign that the eruption was special was the deep origin and primitiveness of its magma composition. Scientists who have studied the lava erupted from the volcano have reported its remarkable characteristics. It rises up from a depth of 15-20 km in the mantle. Several markers of how primitive the magma was turned out to be remarkably high.

Additionally this eruption has broken a very long volcanic dormancy of ~800 years in the entire area of the Rekyjanes Peninsula and the Western Volcanic Zone of Iceland, since the Reyjanes Fires and the massive Hallmundarhraun eruptions took place. This could have consequences regarding the amount of magma available in the area.

The most striking aspect of the eruption is Ragnar, the name that some have been using for the currently active vent. Its size is enormous, over 100 meters tall. Typical eruptions of the Rekjanes Peninsula make cones that are 10-20 meters high, some may perhaps reach up to 50 meters, but as far as I’ve seen none of the eruptions that belong to the 1000 yrs old Reykjanes Fires have created any structure anywhere as tall as Ragnar already is, despite some of them being superior in volume. This seems related to the great intensity of the fountains that constructed the currently active cone. The magma is perhaps very gas rich, as it comes from a considerable depth.

The way Ragnar is rapidly rising the surrounding ground by erupting many short flows on top of each other is also unusual. The eruptions of the Reykjanes Fires, both the slow and fast fissure eruptions, generally send the lava flows far away, making thin, vast sheets. The only exception was Húsfellsbruni, which did behave a little more like Fagradalsfjall. Ragnar however, seems to me, is being much more enthusiastic about its upward growth, by piling up countless small overflows around its prominent cone.

It could already be considered that Ragnar is a shield volcano, because of its growth mainly by overlapping overflows. How big it gets will depend on how long it keeps going. Shields come in all sizes. The eruption could stop tomorrow and end up being a very modest one, but it could also last years, or decades. Many of Iceland’s monogenetic shield volcanoes are more than 500 meters tall, and many kilometres wide, with the very few largest of them reaching volumes of up to 50 km3, being formed in what must have been centuries-long eruptions.

Making the shield with gushing and fountaining.

The reasons why so much material has built up near the vent is that the eruption rates have been very variable. Sometimes fountains burst from the lava lake and spill lava in every direction. Afterward it goes quiet. The eruption may pause completely, shutting off the active lava flows. Each peak of activity leaves a new layer of rock. Layer builds upon layer adding height to volcanic edifice. But why can’t the lava just come out steadily? The answer probably is gas.

Magma contains certain volatile substances which are dissolved in the melt, the main ones being CO2, SO2 and water. The solubility depends on the pressure the magma is under. If pressure is reduced then the volatiles can fight their way out of the liquid and make gas bubbles. As magma rises towards the surface the enormous load of rock above it will be reduced and gas will go free, this will fill the conduit with pressurized gas bubbles, readily expanding, exploding onto the surface in a roaring jet of gasses, carrying along magma fragments. This is what happens in a lava fountain.

Frozen fragment of lava erupted from a lava fountain of Kilauea. Note that the rock is very porous, the magma was full of gas, like a foam, and it froze in this form. From USGS.

I think it can be agreed that the fluctuations in the volcano’s activity are caused by how the gas is released from the magma, as it is the gas what drives the fountain. The exact mechanism may be up to discussion. Here however I will present my views on the two types of activity pulses that Ragnar has demonstrated, gushers, and fountain episodes.

Gushers came in cycles 8-9 minutes long. These happened earlier in the eruption, while now are no longer being observed. These seem to have had to do with the lava pond above the vent acting like a lid. The pond contains magma that falls from the fountains and the bubbling, it has lost most of its gas and as such it is quite dense, it weighs down on the conduit below. Fresh magma is bubbling in the pond. If a batch of fresh magma punches through the whole thickness of the lake it will open a hole in the lid. The hole then reduces the weight acting on the conduit, the gassy magma expands and shoots through the opening, rises in a mighty wave that spills in every direction of the cone, or it sprays bits of magma high up into the air. For a few minutes the hole is open. At some point the pond collapses over the hole and keeps in line the magma column. Eruption pauses. Then magma builds up under the pond until it punches again. This cycle repeats over and over.

What evidence is there to back up this hypothesis? Gushers started at about the same time the lava pond was formed. As the cone grew higher and the pond deeper the gushers stopped, presumably magma could no longer punch through the increased thickness of lava. The 10th of July lava broke from the base of the cone and lowered the height of the lava pond and for a time the gushers returned. Now it is up to the rim again and they no longer happen.

Lava domes that occur in many volcanoes of the world also seem to behave in a somewhat similar manner. A lava dome can be unstable so that the sides often collapse. When part of a dome breaks away this reduces the load on the magma beneath. And what happens? The dome will often explode to bits. A vulcanian eruption it is called. Magma in a conduit is a ticking bomb that is being contained by the weight from above, if the weight is reduced the gas bubbles may go wild. Boom!

Presently Fagradalsfjall has settled into a very different mode of eruption. Fountaining episodes or “paroxysms”.  The activity pauses for about 24 hours. Then activity rises gradually to a peak and an abrubt end follows, also lasting about 24 hours in eruption. I know this type of eruption all too well. Not just Fagradalsfjall, but Mauna Ulu, Pu’u’o’o, Etna, Pacaya, Villarica, Shishaldin, Pavlof, Fuego, have all behaved this way too, and I could really go on and on, naming every active basaltic stratovolcano in the world. With Pu’u’o’o they were termed fountaining episodes. For Etna and Fuego the term paroxysm has been used instead. Etna has been doing frequent paroxysms this year, and so has Pacaya, and probably other volcanoes I do not know of.

This is the way it happens, and it applies to all volcanoes that perform paroxysms. At first the magma in the conduit starts rising and nucleating gas bubbles. It may start to overflow a little from the lip of the crater, or maybe there are some small explosions or spattering which increase in frequency. The eruption picks up speed progressively. Why? When gas bubbles nucleate the magma in the conduit becomes lighter, so that the magma below rises more quickly and nucleates more bubbles, faster than they can escape through the walls of the conduit, more and more the magma becomes increasingly porous until it becomes a exploding jet of gas, a towering column of fire. At some point the magma column lowers enough for the walls of the conduit to collapse inward and clog the vent with rubble. The eruption ends quite abruptly. Black clouds of dust may occur as the walls come down into the collapsing pit. The volcano will now go dormant. However the rubble is weak, so as magma recharges the volcano, it will rise up through the debris, then another paroxysm may bloom into life.

Each volcano will do them in a different way, and even separate conduits that occur within a same volcano will have a characteristic pattern of doing paroxysms. The conduit width is very important, limiting how much speed the rising magma can achieve. Friction against the conduit walls reduce the speed. A tight narrow opening will allow less speed. Mount Etna for example has several summit craters that perform paroxysms, and among them Voragine, the big central one, has usually done the most violent ones. The Southwest Crater instead is young, formed in 1971, and started with small, low intensity events, but has been gaining strength, so that now in 2021, after 50 years of frequent activity, it has practically come to match the power of Voragine in performing eruptions. Each episode will make a new layer of material. With so many paroxysms Etna has grown 30 meters higher this year. Ragnar is not the only volcano growing up!

The storage of the volcano is also important. Fagradalsfjall has no proper reservoir in which to accumulate magma for an eruption so each episode can only throw out a little amount material, but this also means the incoming supply cannot be contained anywhere so that it has to come out to the surface, the episodes will follow each other quickly. At Fagradalsfjall there is an episode every 1-2 days. The Pu’u’o’o eruption of Kilauea during its first years would do much more voluminous paroxysms than Fagradalsfjall, but these happened about a month appart. Pu’u’o’o could release and store a much greater amount of magma that was collected within the summit of Kilauea.

In a way the occurrence of intermittent eruptions in Fagradalsfjall shows that the eruption has evolved beyond a simple fissure. Fissure eruptions do not make fountain episodes. Etna does not make paroxysms when it erupts from its flank.  Etna’s paroxysms occur when it erupts from the four summit craters, the ones that remain semi-open and erupting over and over again, the ones that may have occasional explosions and puffs of gas, that also collapse into pits, and sometimes they do paroxysms.

Fagradalsfjall has evolved beyond its fissure stage of the eruption. Pu’u’o’o and Mauna Ulu, the satellite shields of Kilauea, are satellite volcanoes which have been observed from their birth to their demise. They went through three successive modes of activity. This is a simplification of their highly complex stories, but nonetheless I think useful because it can be generalized to other shield volcano eruptions, including Fagradalsfjall. A shield may go through one, two, or the three stages.

Stage 1. The fissure eruption.

How does a new volcano form? Well if no conduit exists then a conduit is needed. Dykes and sills are the basic form of conduit. If one such intrusion reaches the surface it will open one or more fissures, therefore every new volcano will start from a fissure, and this will of course be stage 1 in the making of a new one.

Pu’u’o’o started with a dyke intrusion and fissure eruption that lasted 20 days, in January 1983. During this stage a large amount of magma was intruded underground creating a dyke. The intrusion acted as a conduit channelling magma from other intrusions that exist within the East Rift Zone, and that are in turn connected to the summit storage of Kilauea, so that a pathway was established from the summit of Kilauea to Pu’u’o’o, part of which already existed, part of which was completed by the dyke.

Another example is Surtsey, 1963-67. An example of a different end-member of fissure eruption. As I have mentioned in some of my articles fissure eruptions can go faster or slower. Pu’u’o’o was a fast one. Kilauea is a mature volcano with a well developed plumbing that allows rapid transport of magma to the eruption site. Surtsey was a new volcano that must have had it much more difficult to get the magma, since it erupted slowly over a period of 3.5 years. The entire eruption of Surtey consisted of a fissure opening phase, with activity shifting between various fissure vents which erupted from the seafloor, and some of them formed islands. It wandered from one place to the other.

Map the vents that erupted in the 1963-67 Surtsey eruption. From wikimedia, by Pinpin.

Despite being a fissure eruption, Surtsey did build a shield volcano, or better said two small shield volcanoes. Surtur and Surtungur. These two vents erupted enough material to form an island and erupt onto dry ground. They became effusive and started producing gusher events. Yes, like those of Ragnar. Lava would burst spectacularly from lava ponds and send lava overflows rushing into the ocean at up to 70 km/hour. These gushers built two twin shields, each 90 meters height.

Going back to the Fagradalsfjall eruption it was preceded by a lengthy intrusion, that went for 3 weeks before breaching the surface, on March 19, and establish a pathway for magma to flow from the depths of the earth to the surface. Of the multiple fissure vents that opened, Fissure 5, or “Ragnar”, was the most successful. Ragnar went on to erupt with an open channel that fed an aa flow and rubbly pahoehoe. Afterward came the gusher events. Initially gushers started like high fountains which went into the lava channel, but over time they took the form of spectacular surges which went down many sides of the cone. The surges added layer over layer. Ragnar’s shield growth had commenced.

The first pause of Ragnar’s activity on June 28, I take it as the start of the second stage.

Fagradalsfjall eruption on April 5. Fissures are opening up.


Stage 2. Intermittent eruptions from the central vent

When an eruption pauses and the conduit becomes clogged, the magma may need a new opening. If lava rises up to the surface and erupts again without the need of a dyke then it can no longer be considered a fissure eruption. When Pu’u’o’o started Episode 2, or when Ragnar came back to life on June 29, they did not need a new dyke, instead they re-established the previous conduit, and as such they went beyond a fissure and entered a new mode of erupting. From now on the magma column may disappear back into the ground. The crater may look empty and dead. However magma rises up through the rubble and the volcano is reborn. This happens repeatedly. Pu’u’o’o had 46 fountaining episodes, not counting the initial fissure stage. I‘m not sure how many Ragnar has done already, they are happening frequently, every 1-2 days.

Lava fountain shooting from Pu’u’o’o during episode number 23. The lava explodes into pieces of spatter but then as they land on the ground, reassemble into lava flows. From USGS.

Pu’u’o’o had the storage of Kilauea as a reservoir to hold magma. It could erupt a lot, and very fast. Initial episodes erupted just over 100 m3/second, but the intensity grew systematically so that the final fountain episodes were erupting at more than 1000 m3/second.

Other eruptions of Kilauea that involved high fountains, Kilauea Iki 1959 and Mauna Ulu 1969-74 also increased the intensity of the fountains over time. This seems to have had to do with a widening of the conduit, which reduced friction against the walls, and allowed the magma to achieve greater speeds. This widening was well recorded with Mauna Ulu. In just about a year the conduit of Mauna Ulu grew from being a 1-4 m wide dike, to 100 meters wide double cylindrical pipes. By this time the eruption was into “stage 3”. Fountains had shut off much earlier. Perhaps because the conduit was so wide that it could no longer build enough gas to burst into a jet.

Conduit of Mauna Ulu was eroded into the bedrock. It forms a pipe 100 meters wide. This is seen when the magma column had dropped down. The subterranean passage feeding towards Alae can be seen as a gaping hole through the wall of the pipe. Black, still, molten lava is visible in the bottom. From USGS.

When a conduit is very wide, and the magma fluid, the top becomes a lava lake which is in permanent circulation, moving up and down, the places where the magma comes up usually have a still surface, those spots where magma sinks into the depths have spattering that releases gas into the air. A convecting lava lake degasses efficiently, which is perhaps the reason why they are never seen to burst into high fountains. Convecting lava lakes are for example the pre-2018 Halema’uma’u of Kilauea, the former lake of Nyiragongo, Erta Ale, Masaya, or the 4 former lava lakes of Ambrym.

Lava lake inside Pu’u’o’o. The spattering along the walls shows that there is convection occurring. The cold lava sinks down along the contact with the wall. Bubbles resist to be carried down and are released with bursts of spatter. From USGS.

But that is what may happen in “stage 3”. Stage 2 instead consists of eruptions from a central pipe that feature fountains. Fagradalsfjall doesn’t possess magma storage which places a limit on how big or fast the episodes can be. This makes many small episodes that are rapidly rising up the ground next to the vent.

Many of the largest shields of Iceland seem to be made many surface streams of both pahoehoe and aa lava which issued from the top of the volcano and ran downslope. They seem to have been formed by many episodes of eruption. This seems similar to Fagradalsfjall now. The large shields often have a height of ~500 meters above their base.

The bright lava flows are pahoehoe type, the black-brown lava flows are aa type. Pu’u’o’o eruption. From USGS.

The shields of Iceland are most of them many thousands of years old, and are not well preserved, but I have found several monogenetic shields in Arabia that are similar, and very young, perhaps historical. One the biggest ones is Jabal al Qidr, located in the Harrat Khaybar volcanic field. Jabal al Qidr is 300 meters tall. It is formed mainly by black flows of aa lava. They grade upslope into pahoehoe flows, that form a more silvery collar around the crater of Jabal al Qidr. The flows probably flowed in smooth rivers near their source but were rapidly shattered into clinkery aa as they rushed down the steep slopes of the shield.

Jabal al Qidr in a satellite image from NASA.

Jabal al Qidr monogenetic shield volcano seen from the side. From Google Earth.

Stage 3. Sustained effusion from flank vents

Both the Mauna Ulu and Pu’u’o’o satellite shields of Kilauea entered a final phase of eruption during which the main conduit fed radial dykes, which resulted in flank vents. These openings in the flanks erupted slowly but steadily, and fed lava tubes that reached very far away, often pouring lava into the ocean. The main side-vent of Mauna Ulu was the Alae shield, the lava that continually flowed underground between the two locations started eroding the ground and eventually formed a small canyon 530 meters long and 40 to 60 meters wide, floored with hot, steaming rubble, through which lava could sometimes be seen.

The Alae shield in the foreground, flank vent of Mauna Ulu. Mauna Ulu itself rises up behind. September 8, 1972. From USGS.

Lava erosion formed a small canyon along the magma pathway between Mauna Ulu and Alae. May 25, 1972. From USGS.

Pu’u’o’o also had numerous flank vents throughout its 35 year long eruption, and practically all the volume of the eruption was produced by the flank vents not the summit. The long steady eruptions eroded the flanks of Pu’u’o’o too. The erosion formed a complex of pit craters known as Puka Nui.

The top of Pu’u’o’o and Mauna Ulu would feature an open convecting lava lake, or else the conduit was roofed over and erupted from many small openings, ponds, and spatter cones, which sometimes produced small fountain episodes that were like miniature versions of the episodes in their second stages. When the volcanoes drained, the top collapsed into a pit crater, sometimes quite deeply. One collapse of Mauna Ulu led to a months-long dormancy, afterwards however the magma had no trouble in rising up through the rubble, quietly without a single earthquake, nor any sign of its movement, and resumed its activity.

Many small conduits issue from the central conduit of Pu’u’o’o and erupt across the crater, like a chandelier. From the USGS.

All or almost all shield volcanoes of Iceland do show extensive tube-fed flows which form an apron around the main cone. Usually it is not clear though, if these came from the summit, or from flank vents. Or if their exact timing in the eruptions. There is one shield, Kollóttadyngja, which has a 2 km long lava erosion feature, consisting of a chain of pits. It looks like this chain possibly marks the pathway from the shield to vents on the lower southern side, where vents issued lava tubes which in turn reach 25 kilometres away. This activity seems to be have been among the latest events of the eruption. It is hard however to reconstruct an eruption based only in its morphology.

Kollóttadyngja shield volcano, looking from the south. The top of the cone had a 400×600 m perched lava lake. A chain of pits possibly marks a magma pathway which fed the lava tube eruptions that issue from the base of the shield. There are also many small fissure eruptions issuing from the sides of Kollóttadyngja, which is hard to know if they were part of the eruption or later events. From Google Earth.

Some shield volcanoes, like those of the Snake River Plain in the U.S., do show clearly that first a central shield was constructed from  many small overflows, and then later lava erupted from secondary openings along the lower flanks of the shields and they fed a voluminous apron of inflated pahoehoe, with lava transported through tubes inside the flow.

The 100 meters high Pillar Butte shield volcano, located in the Snake River Plain, lies in the centre of the image. It is formed by contrasting, bright and dark flows, of pahoehoe and aa lava. It is surrounded by a large apron of inflated pahoehoe fed from its flank and formed in the last stages and dwarfs the shield itself. From Google Earth.

Another shield volcano in island of Santiago, in the Galapagos Islands, features many radial spatter ramparts, dykes that propagated from the central conduit tore cut open the slopes and in turn feed lava tubes and flows.

Volcano in the Galapagos Islands. Fissures and single vents are marked with red lines and circles.

Jabal al Qidr, in Saudi Arabia, has a group of flank vents on its northern slope. They formed towards the later part of the eruption. These vents however did not erupt slowly, instead they produced rapid floods of lava. Sheet pahoehoe flows that must have been formed violently. One possibility is that they were a series of catastrophic drainings of the lava lake at the top of the shield.

There is another vent 8 kilometres north of Jabal al Qidr, which looks of about the same age. It erupted mainly tube-fed flows that reached distances of up to 50 kilometres from the vent, and must have formed at very low eruption rates that were held steadily for a long time. This vent could have been a flank eruption of Jabal al Qidr, but this is hard to know for sure.

Rootless volcanic shields form from overflows fed from multiple openings above a lava tube. The lava tube extends from a vent 8 km north of Jabal al Qidr. From Google Earth.

If the Fagradalsfjall eruption goes on for long enough it is possible that it will go into this mode of activity. Although it would be best for people who live near the volcano that it reaches no further than stage 2. Tube fed flows may reach very far away and cause destruction in populated areas.

This is quite a complex eruption that we are seeing unfold, and there might be a lot to be learn about how volcanoes grow. and how their plumbings work. It is hard to make any estimate of its duration, it could end tomorrow or it could last decades. Shield volcanoes do come in all sizes. We shall see. As much as the fog and the night allow.

268 thoughts on “Making a shield volcano

    • Two noticeable jolts on the faf fra drumplot during the last 24 hours. Could a blockage have been introduced?

      • I was wondering about wall collapse? We know that the lava level receded, perhaps some of the wall has caved in?

      • I was thinking that, too. Two small collapses inside the conduit? The first looks to have been 5 kilometres down, the second a very similar depth (making a dozy guesstimate from the earthquake tables for the area).
        So, a collapse in the conduit at 5km? In which case we can either expect a very strong, gassy throat-clearing blow-out, or it could signal eruption’s end.

      • The volcano is just like one of these cranky stars that refuse to leave the dressing room when the show starts. Something is wrong, maybe the lighting or the weather, the payment, who knows. And maybe he’s even drinking.

        • Nar looks to be smoking. I consider that rather odd, because I’d heard that the area was a designated no-smoking area.

    • We are now 6 months later, and this volcano is developing pretty much as the author described.
      The pilot light may be out, but the magma is still rising, with this week’s display confirming a phase II development.

    • And here’s the IMO news report:

      There’s been a run of interesting events at Askja in the last few years. From memory (so probably faulty): a substantial landslide on the S side of the caldera; the lake has, unusually, not fully frozen some years; and then there were reports of an (unexplained) “bump”.

      Carl has suggested Askja is one to watch, so perhaps its building up to something. Though from the IMO report, it looks like it’s issued false alarms in the past.

  1. Some slight increase on the tremor plots now and also a tiny hot spot on the Keylir thermal cam (perhaps from the lava fields, perhaps starting activty).

    • The magma chamber a few km down have grown in size, and its takes longer to fill up that with gas pressure

      The next eruption may last almost
      2 days If this is the case, but just a speculation..

      I think We may end up with a big shield here ( perhaps ) ?

      It have not yet entered constant slow effusion of lava

    • Nice to see the cameras back so that they can show us some more fog too 😀.

      Its a bit frustrating not being able to get a clear view of the action, but still awesome that we get to see it from time to time.

      Hats off to the teams that maintain the cameras in fairly challenging conditions.

      • Reminds me of contemplating a piece of toilet graffiti many, many years ago.
        Here I sit, broken-hearted
        Paid my penny and only farted.

      • Hah ha! Thanks for the rhyme.

        I think the pressure is back on. There’s plenty of ‘rumble’ in the drumplot, too.
        If we had a collapse in the conduit, prepare for a bit of a throat-clearing (hopefully) 🙂

      • Maybe the crater has filled in and is shallow again, so we get massive fountains instead of lake overflows again.

        I expect it is not yet done, it is hard to stop an open conduit, it might be collecting in a magma chamber which is going to slowly increase the time intervals but also the volume of each episode.

      • Fog clearing on the MBL close-up cam (which is now on Stóri-hrútur) and the crater rim is looking very ragged.

        • At the moment it almost looks like he’s producing a huge rabbit. Nothing too surprising after all.

  2. Looks like Kilauea has stopped sending magma southwest and is continuing to inflate, for being a sizable intrusion it hasnt really done anything, maybe delayed the next eruption by a few weeks. There are still tremors on the seismometers, even if they are deep that is a lot of magma moving somewhere.

    • It have failed again ..

      I think it will be years before We gets another open conduit lava lake

      2021 eruption was just a small intrusion into the caldera floor

      Is there any chance for a real circulating lava lake soon?

      • RE:”I think it will be years before We gets another open conduit lava lake..”

        The black and white stills and films of pre-1924 Halma’u’ma’u’ are sad compared to the video images we enjoy today.A return of something like that would be quite a study. I don’t think even Pu’u’O’o’ in its time compared.

        • 1920s lake was about as big as Pu’u O’o until 1921, it was not as big as Halemaumau in 2018 was. 2021 had a major overflow that included several radial vents as well as apparently a batch of viscous basalt which lead to some violent fountaining and tephra cone formation on the west side of the lake. There’s not a lot of info or much of a geological record but it seems to have left quite an impression on Thomas Jagger, founder and then head of HVO, and he saw some significant eruptions at Mauna Loa so this means something. I imagine it looked something a bit like what we see at Fagradalshraun but with more complex lava movement in the crater.

          1921-1924 though the lake was massive, 500 meters wide, until it drained. But I think most of the old pictures are before this.

          Anyway most certainly this can happen now. To me though it is more likely to be on the ERZ again, maybe next to or in Napau crater, or a bit east of Pu’u O’o, maybe much east of Pu’u O’o down near Heiheiahulu and highway 130, which is as far east as the south flank quakes go which show spreading. Maybe even the other direction entirely on the SWRZ at the Kamakaia hills, that is possible too now after this fortnight. The summit does shields when the rifts are inactive, evidently that is not the situation we are in right now. 2018 didnt drain enough magma to cut off the rifts, we would see pit craters form and reform, and massive broad subsidence, and Etna-type fountains from the ring faults for months. 2018 was not the terminator it was a taste of what is still to come… Lets just say Veidivotn has got come competition.

          • RE: “1921-1924 though the lake was massive, 500 meters wide, until it drained. But I think most of the old pictures are before this…”

            Apparently. In Jaggar’s book, save for two small photos captured in Jan/Feb 1924, before the steamblast eruption, which changed the dimensions of the crater, all the photos of the lake are 1921 or prior.

          • Yes, unfortunate really, the 1921-1924 lake was as big as the one back in December last year when it was fully liquid, but stable and convecting for 3 years like that. Recent Nyiragongo and Overlook lakes were possibly more voluminous, they were much deeper, but physical size you could fit both of them inside the 1924 lake…

            I expect maybe just for a short time we will see that again later this year though, next eruption in Halemaumau. Will be a good visual 🙂

      • Kilaūea haves an enormous magma supply at current era
        I hopes she will provide with something soon

        Most fun woud be a lava lake shield in the summit caldera with caldera filling up and tube feed pahoehoe spreads all over ERZ .. been huge shields over the summit before althrough they collapsed in caldera formations

        • RE: “Most fun would be a lava lake shield…………………”

          Not planning to run for local office at Volcano Village or anywhere else remaining viable in the SE corner of ‘The Big Island’ are you???

    • Or chance for a huge shield at the summit? With its large supply .. it should be

      Coud Puu Oo also come to life again?

      • More ERZ shields, probably but not certainly east of Pu’u O’o. Summit will not do shields until the ERZ connector is cut off. The Observatory shield formed inside the Powers caldera, that was truly massive, its deep pit was possibly as wide as the entire outer caldera fault today, same league as the biggest of the Icelandic calderas. Probably it represents the final tier caldera todays system can make, forming incrementally and getting bigger with time through multiple ERZ episodes. The Uwekahuna ash and Powers caldera are both analogous to today, but bigger, which means today is not the end of the cycle, probably nowhere even close.

  3. Geldingadalir charts remind me of a pressure cooker. I get the impression she wants to erupt but is blocked.

    • My impression is that the crater was blocked by larger than usual collapses. Eventually the lava will come through again. It is trying

      • What seems odd to me is that most of the other stations shown on this website: are also trying to do the same thing as FAF. So many of them are showing an upward slope all day today even though their usual tracks do not resemble FAF’s. Is this a coincidence, or is something going on that affects a wider area than usual?

    • Could the caldera collapse, blocking the exit of the lava, cause a more explosive eruption?

      • Probably not in itself. Rubble isn’t strong enough to contain highly overpressured gas. It becomes different if the eruption pauses long enough that the lava in the rubble solidifies, as that gives a much stronger layer.

  4. Again I am struck by how bad I am at judging what has happened to the volcano in about a week, I was thinking yeah It’s crumbled a bit it height but not much else has really happened. Well here is the difference between August 26th and September 4th, it has changed quite a bit in the fog:

    • It appears that part of the big carapace overhanging the central lava lake has collapsed into the pit. We know that 2 events occurred, my guess is rock failure close to the top of the cone, or certainly the last 100 meters or so.

  5. Tremor experts: why would the purple tremor still be rising, but not the blue?

    • I was just thinking the same. I think the system tried, and failed to produce another eruption.
      Something blocked the conduit @5km down (my guesstimate – see post up above somewhere).

    • The conduit will be hard to kill
      Its act as s syringe sucking up magma. Its also well heated now to 1240 C and some of that heat is in the walls too now after a few months

  6. The Geldingadalir volcano is looking like a rather lopsided shield these days, as we all can see. One side’s a classic shield apron, but the other side is still rather steep (the original spatter cone of course), all because lava’s mostly coming out of one side.

    Now, I have to wonder if it’s only a matter of time before the steep side collapses big time – and releases a HUGE flood of lava in the process. This’d be a pretty spectacular sight, especially if viewed from a drone!

    • It actually did exactly this last time it erupted, the cone didnt fully collapse but there was a massive lava flood and a lava lake in Geldingadalir.

  7. This is a time/depth plot of the quakes

    in this area of the SWRZ (Kikauea)

    Looks to be moving up…

    • GPS OUTL is showing a trend back to going south, so no magma going down into the SWRZ, but there is also a possible resumed upward movement there, it seems magma is accumulating in the area still. I expect this could erupt soon, there was an eruption here in 1982. Might not be so big if it is here, being high above sea level, I think an eruption in the deep pit of Halemaumau will be much bigger, but really who knows if the pressure is there then the elevation doesnt really matter and this is also a different magma chamber…

      Whatever it is I think it will be extremely sudden, there will be a swarm of quakes and lava on the surface in an hour. Eruption from these magma chambers are also very intense, sub-single day curtains of fire, mini flood basalts.

  8. The FAF tremor graph shows what looks like a failed eruption, and a similar peak shows up at many other stations in the area. Perhaps the lava flowed into a sill?

      • Well spotted, it did behave a bit different than most eruptions, I was thinking yesterday that it’s unusual that the purple starts to go up before the blue and green basically has crossed it, so suppose wind gives a slightly different signature, but tremor plots are quite difficult to interpret at times for sure.. But should have thought of it as when I was trying to get a good image for the vocano outline series the wind was shaking the langihryggur camera around something fierce.

    • A sill could still be happening, it might be expected even. This would be pretty much aseismic just showing up as inflation. It might not necessarily erupt though, not unless it can create another dike to the surface. But really who knows there was a point the eruption was quiet for longer than this pause has gone so far, and other open conduits have resumed after much longer, so long that under ordinary circumstances it would have been considered two separate eruptions, Mauna Ulu and Etna for example.

  9. Fagradals…Having a rummage through the charts this morning proves a bit disappointing. It looks like the intrusion has done little or nothing since the last eruption.
    As Rob demonstrated, the recent peak in signal was likely to be weather.

    I’ll contact the Co-op funeral services…

      • I think we all just need believe with the eruption is over.. usually when experts say that the volcano springs back to life, so at least I am sure the eruption is over 😉

  10. South Sandwich Islands quake swarm is still ongoing, been nearly a month now.
    There’s now been over 1000 aftershocks, 500 above M4.5 size.
    Started with a large foreshock (M7.5) and then the joint largest recorded quake in the region (M8.1).
    For the record, 3 M8+ so far this year, which is more than usual, but doesn’t mean the apocalypse is upon us.

    Wonder what prolongs these swarms, could there be a volcano-tectonic element a la Iceland? I’d be surprised if the reasonably active volcanic arc hasn’t been affected by this.

    • For the record, 3 M8+ so far this year, which is more than usual, but doesn’t mean the apocalypse is upon us.

      At least, not until you factor in that there’s a plague and insane politics everywhere and ludicrous hurricanes and half the west coast is on fire and the saber-rattling between the US and China lately that could lead to World War III … I think that’s all four horsemen and then some.

      • Fortunately I live in the UK, I say fortunately but our government and politics are only slightly less batsh** and corrupt than the US these days. We do tend to steer clear of natural disasters though, and have had a fair few extended heatwaves this year, albeit the last week has been slightly rainy. Seem to be doing alright on the Covid deaths too though cases have picked up, not too worried though.

        One thing we do have is an insane neighbour trying to push a case for independence despite being funded by the central government and having the highest drug death and covid death rate in europe, tax evasions, allowing 4 year olds to pick their gender without parents permission and 1/4 of their MPs currently under investigation for something or other.
        (The SNP for anyone who’s reading.)

        • I’m a Scottish independence supporter, and a Scot, and Scotland has had enough of being ruled by another country, when the last time Scotland voted Tory majority was in 1955… The reason why Scotland is funded by UK government is because it has been stealing our resources since 1707, we don’t want fascism, right wing lunatics having power over us, Scotland will be free soon!

          • This discussion is best for the bar. I recommend an Irish stout

          • This gave rise to comments that were intercepted by our filter. They objected to terms used to describe the opposition. That is a fair point. Emotions can go a bit high in the absence of a decent lava flow

          • And yet the comment hasn’t been removed, but mine was rejected…

          • No apologies needed, just awareness that people have different opinions and experiences. None of these issues are as straightforward as they are sometimes made out. Yes, money flows from London to support the UK regions and nations, but at the same time government funding for London is much higher than for those regions. An example is education funding: schools in London receive 20% more per child than in the north of England. I am sure other countries have similar issues. There are two sides to all stories.

            And this too should have been in the bar..

  11. Something odd on this webcam — close up — starting at about 01:41. What I think of as Clive’s parasitic vent starts to glow faintly, and a few minutes later the camera shifts to show some light to the left of the cone.

    What do you make of that?

    • There has been some glow from some parts visible when it’s been clear and dark from two spots, so believe that is just some glow from those, then the camera pans over to Grindavik.. My interpretation at least..

    • Left of cone, I’d guess there was a wall collapse revealing some very hot cinders that then cooled off.
      Can’t see anything from extra cones? Mind you the time sequence is slipping out of availability now.

  12. Double success on Mars. Sample 2 is still in place and Ingenuity completed Flight 13

    This is the confirmation that we’ve been waiting for!! Our very first captured sample! Here’s my HDR merge version of the two of the Mastcam-Z images. You can clearly see the sample nestled safely inside the tube, due to better lighting from the sun this time. #SamplingMars


    Happy Flight the 13th!

    Ingenuity has achieved its 13th successful flight on Mars. It traveled at 7.3 mph (3.3 m/s) taking images pointing southwest of the South Seítah region. This aerial scouting continues to aid in planning @NASAPersevere
    ’s next moves.

      • The current plan is a joint mission between NASA/ESA involving a fetch rover, launcher and sample return orbiter. Elon plans to be on Mars before then but “Elon Time” is known to be optimistic 🙂

        Mars Ascent Vehicle from Northrop Grumman takes shape for Mars Sample Return mission

        On the heels of the successful landing, NASA formally awarded the MAV contract to Northrop Grumman.

        A 2019 graphic depiction the proposed mission architecture for Mars Sample Return. (Credit: ESA)

        Other critical parts of the mission, the Earth Return Orbiter and Sample Fetch Rover, will be provided by ESA, along with the lander’s robotic arm. In addition to the MAV, NASA is providing the Sample Retrieval Lander and the Capture and Containment and Return System payload on the Earth Return Orbiter.

        To discuss the initial concepts for the MAV, NASASpaceflight spoke with Northrop Grumman about the project and its current state of development and criteria.

        …McGrath added, “I can imagine the various orbiting spacecraft at Mars are going to have a play in ‘what’s the weather like?’ Maybe what has to happen is the lander itself will have to have some anemometers for wind. Maybe the Ingenuity helicopter will still be operational at that point. Hard to say, we’re talking several years out now.”

  13. There are numerous small hot spots on the surface of the cone. Vog is also streaming from multiple points in and near it, mostly around its rim. No flowing or spattering lava in evidence, though, and the tremor keeps doing the cha-cha…

    I don’t suppose an RUV technician will be along soon, now that the weather is good for travel, to fix their broken volcano? 🙂

    • If you look carefully at that FAF tremor graph you can see a message written in 8000 year old cursive runes. It says, “On strike. Feed me human sacrifice. No belt buckles or metal zips.”

  14. ”Eeeeee! Eeee! Nooo! Noooooooo!
    Myy Preeeeecuuuuioussssss is loooost!!!”
    Gollum screaming

    Looks like Fagradalshraun may have runned out of gas, or having degassed most of the volatiles in the supply 20 km down. After all gas that expands in a magmatic liquid is what drives it to the surface.Just like a coke bottle.
    Perhaps the moho resovair have degassed enough now

    But its an open conduit there now and its perhaps hard to kill once formed. I dont think our wonderful tourist eruption is over yet .. 🙂 but we will see

  15. The jökulhlaup from the Skaftá cauldrons continue. Now that the hlaup from the western cauldron is declining, the eastern is joining in. Floods from the eastern cauldron are larger than those from the western and now that the hlaup from the western cauldron has saturated the ground water there is a big chance that the eastern hlaup will flood larger areas than the last time in 2018.

    • It’s getting on for 24 hours since IMO posted that report but there’s no significant increase in the discharge rate on the Skafta at Sveinstindur. At a guesstimate from IMO info about the W cauldron hlaup, I think we’d expect something to show at Sveinstindur within 12 hours.

      On the other hand, if the hlaup does happen, maybe at last, with the water pressure removed, Grimsvotn will have its chance to show that there are tourist eruptions and then there are Big Bangs!

      • This is still not Grímsvötn. The cauldrons are to the northwest and belong to Loki-Fögrufjöll. The current hlaup may flood the areas downstream, but will not affect the probability of a Grímsvötn eruption.

      • Not Grimsvotn draining out though, Skafta cauldrons are hydrothermal features. Been supposedly on the verge of erupting for a year now, maybe not the best call.
        2011 was a big eruption about equivalent to 20 years resupply, so really maybe we are jumping ahead of ourselves a bit thinking it will blow its top again in half that time.
        The melt generation rate deep down under Vatnajokull is colossal it could be even higher than Hawaii, but probably very little of that melt actually reaches the magma chamber feeding Grimsvotn. Its supply I have found is maybe 1.5 km3 a century, 2011 was 0.3 km3 DRE, 1996 was 0.4 km3, so maybe best to look elsewhere for the big bang. Bardarbunga is larger, 2.5 km3 a century, though Holuhraun was about 1.5 km3, so could be a while there too.

        Hekla is 2 km3 a century, and has no deep rift to steel magma, it is also 1/5 the way through that century without doing anything yet, just saying 🙂

        • Thanks, guys. I thought I had read somewhere that it was the current cauldrons’ draining that could contribute to triggering Grimsvotn but you have jogged my memory: it was the lake at Grimsvotn itself that people were discussing. Absence of lava at Fagradalsfjall must have got me over-excited.

          And in relation to Grimsvotn’s preparedness to erupt, the data are highly suggestive, and again, have been the source of quite a bit of speculation on here in recent months. And G was put on Yellow status in recent months, too.

          1999-2004 eruption: 2,119 days
          2004-2011 eruption: 2,375 days
          2011-present: 3,754 days

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