This is a repost of a guest post by volcanologist Dave McGarvie, first published here in 2017. Dave is currently associated with the Lancaster Environment Centre of Lancaster University; at the time of writing this post he was working at the Open University. He studies volcanoes in Iceland and Chile and can be found at https://research.lancaster-university.uk/en/persons/dave-mcgarvie/
As a preface to this post, it is worth noting that this ignimbrite is nowadays indeed considered to be associated with the collapse of the Torfajökull caldera (as already mentioned in Dave’s post). The caldera-forming eruption is dated to either 55 thousand years ago, based on argon dating by Jonathan Moler, which would associate it with the Icelandic rhyolitic Z2 Ash, itself a component of North Atlantic Ash Zone II. (A younger date of 38 thousand years ago is derived based on zircon crystal dating, in work by Zoe Moser.) Torfajökull (the name means Torfi’s glacier) is one of the wonders of Iceland: see https://www.volcanocafe.org/the-new-lagoon-and-icelands-thor-adventure-park/ (which regrettably was about possibility rather than reality).
And now over the author:
One of the wonderful aspects of working as a volcanologist is Iceland is that fascinating new puzzles and their bigger cousins (enigmas) keep appearing. Sometimes even a fresh look at what seems to have been fully ‘sorted’ decades ago can – with the benefit of newer knowledge/understanding – result in enigmas re-emerging.
Welcome to the Thórsmörk Ignimbrite.
Author’s Note:
What is an Ignimbrite? An ignimbrite is simply the rock that forms from the deposition of one or more pyroclastic flows*. Something extra needs to happen to convert the loose aggregation of pyroclasts and rock fragments that comprise a pyroclastic flow deposit into a rock (ignimbrite). Fortunately, pyroclastic flows are surprising good at retaining much of their heat during transport, so once they come to a halt this heat can cause sintering and welding – and thus the formation of a rock (ignimbrite) that is much more resistant to erosion. Compaction of the pyroclastic flow deposit can also occur, and again this transforms the deposit into something more rock-like. There are a host of other post-emplacement processes that affect pyroclastic flow deposits, but we’ll leave these as they are less relevant to this particular article. In the field, ignimbrites have textures too variable to describe briefly here. Fortunately, the Thorsmörk Ignimbrite is a bit simpler and has an ash matrix (light or dark coloured) with a scattering of pale-coloured pumices and rock fragments. These reflect the components of the original pyroclastic flow – ash and pumice being fragmented magma, and rock fragments being chunks of older rocks that were fractured and pulverised during the eruption (e.g. vent walls). For simplicity, I’ll refer to the ignimbrite as either welded, part-welded, or unwelded. *Note that I have chosen to use the term ‘pyroclastic flow’ instead of the jargon term ‘Pyroclastic Density Current’ (PDC for short), as I consider PDC a cumbersome and partly-misleading term.
Introduction
I first looked at the Thórsmörk Ignimbrite in September 2013, and after a couple of days in the field followed by some literature reading, I realised that there were still many unanswered research questions about the Thórsmörk Ignimbrite. Here’s a few of them:
1. When was this pyroclastic deposit erupted?
2. What was the source?
3. Is there just one ignimbrite present, or are there more?
4. What was the environment like when it was deposited?
5. What processes affected the ignimbrite soon after it was deposited?
6. Why are there dark and pale phases – are they the same chemically but just different physically?
7. Why is there so much reworking, and why had previous authors not mentioned it?
8. What do fragments of welded ignimbrite within overlying unwelded ignimbrite tell us about time gaps etc?
9. What did the original complete PDC stratigraphy look like?
10. When did the processes that jumbled the ignimbrite occur – during deposition, during welding, or post-welding (or some combination of the three)?
The answers to 1 and 2 are being worked on as I write, by PhD student Jonathan Moles (http://www.open.ac.uk/people/jdm539) The provisional and exciting answer to 2 appears to be Torfajökull to the NNE, but that’s a story for another time….
Figure 1
Figure 1 shows the location of the various volcanoes in southern Iceland along with exposures of the Thórsmörk Ignimbrite (in green).
Nobody is currently doing serious and comprehensive studies on the Thórsmörk Ignimbrite, so many of these questions will remain unanswered for the foreseeable future.
So, the aim of this blog article is just to give you some insight into what I’ve gleaned from a few days of fieldwork, and I’ll mainly address points 4-6 above. As this is recce-level work a nice robust model can’t be provided (it would be too speculative for my liking), but I hope that you will get a bit of insight into what volcanologists do in the field, complete with uncertainties, challenges etc.
Finally, another reason for this field-based article with lots of images is that this area is very accessible, and so if you – dear reader – wished to have a look for yourself, it is straightforward to do so. I’ll be happy to provide details of specific locations. Now, onto the nitty gritty.
Variations and themes
Figure 2
The first thing that struck me about the Thórsmörk Ignimbrite was its variability. From the logs in papers published back in the 1980s (see list at the end) I was expecting simple horizontal or gently dipping boundaries between different flow/cooling units that could be traced for hundreds of metres. Instead, it’s a mess, with different varieties of ignimbrite jumbled together on the scale of tens of metres. For example, look at Figure 2, which is c.300 long. Having looked at outcrops that appeared in published papers with Jonathan Moles and ignimbrite expert Becky Williams we could not reconcile the complexities that were in front of our eyes with the simple logs in the published papers. This was very odd.
Several simple observations can be made from Figure 2: the base is not exposed; the top is exposed and is capped with sediments (which reassuringly contain clasts (i.e. chunks) of the Thórsmörk Ignimbrite – so the sediments are younger); there are pale and dark varieties; welding is variable; there is reworking of unwelded deposits. Yes, it really is a mess. The burning research question is – is this mess a mess related to original variable deposition of the PDCs, or is the mess due to later processes that moved separate ignimbrite domains in a way that brought them together?
So, let’s try and find some simpler exposures that might help us shed light on this variability. This is a common survival tactic when faced with a difficult field problem – go and look for simpler examples to understand first, then come back to the complex stuff.
Figure 3
Figure 3 (courtesy of Jonathan Moles) shows some of his mapping of southern Tindfjallajökull, where the Thórsmörk Ignimbrite occurs within a series of sedimentary units (tills) which – due to matrix and clast characteristics – we interpret as being glacial in origin. These units thin towards the margins of an ancient basin located in SE Tindfjallajökull, and in Figure 3 they can be seen thinning up to the right (towards the basin margin) with the ignimbrite sandwiched between tills. But is the complete ignimbrite preserved here?
Figure 4
No. Figure 4 shows that only one variety of ignimbrite is found – a part-welded dark phase. And although it looks simple from a distance, in detail it’s not as there are pods of other ignimbrite varieties around, such as the welded pale variety, and some unwelded ash. Yes, it’s still a puzzle.
But this area did demonstrate an interesting and previously-unknown feature of the local eruptive environment at the time the ignimbrite was being deposited – that a basin was filling with diamict (glacial sediments), and that this continued after the ignimbrite was deposited. The only difference between the diamicts below and above the ignimbrite is that the ones above contain clasts of ignimbrite.
Figure 5
A further look at ignimbrite exposures in this basin uncovered further complexity, including larger exposures of welded pale ignimbrite, further (rare) exposures of ash at the base, and that as well as being sandwiched within diamicts, the ignimbrite is also sitting directly on top of old basement rocks (pre-Tindfjallajökull), as shown in Figure 5. The latter merely indicates that the pre-ignimbrite topography was irregular, and that diamict was deposited irregularly.
Figure 6
Interesting insights into past environments that can be made from fieldwork in this area, is what happened after the ignimbrite was deposited. In many locations, subglacial basalts overlie the diamicts sitting on top of the ignimbrite (Figure 6). Logically, ignimbrite and diamict deposition would have required little or no ice to be present, but for subglacial basalts to be confined the ice must have been much thicker. So, it’s reasonable to conclude that a period of sustained cooling occurred after deposition of the ignimbrite. This points to a major environmental change after the eruption that formed the ignimbrite. See overlying subglacial basalts on Figure 6, and on Figures 3 and 4. And on Figure 7 (to come).
Figure 7
What else happened after the ignimbrite was erupted?
As well as the evidence for substantial subglacial basalt eruptions in SE Tindfjallajökull after diamicts had been deposited on top of the ignimbrite (as the basalts lie on top of the diamicts – see Figures 3, 4, 6, and 7), there is evidence in other locations that prior to subglacial basalt eruptions there was an episode of ‘reworking’ of the ignimbrite, involving especially the unwelded parts but also the welded part. In Figure 2 the label ‘reworked pale’ appears, and this reworked pale appears in many locations. Let’s look at a great exposure in Steinsholtsdalur, to the NE of Eyjafjallajökull.
In this location, there is the most spectacular and largest exposure of reworked Thórsmörk Ignimbrite that I have seen – but as I’ve not been everywhere, bigger and better ones may exist. At this exposure, reworked pale and unwelded pale ignimbrite occurs, and both are truncated by a subglacial basalt. The subglacial basalt is connected to small dykes that have intruded reworked ignimbrite, and in places the dykes have sintered (baked) the unwelded ignimbrite. Figure 7 shows Hugh Tuffen (@htuffen) and Lancaster University Masters student Alastair Hodgetts collecting sintered ignimbrite samples for lab analysis.
Figure 8
This is a marvellous exposure, and one worth spending days trying to decipher. For example, Figure 8 shows some detail of the reworked pale, with pumice-rich lenses and small faults affecting the finer-grained domains, and Figure 9 shows uppermost reworked pale cut by overlying subglacial basaltic volcaniclastics. There’s a great story to be uncovered.
Figure 9
Figure 10 reveals another puzzle about the reworked pale ignimbrite. Here, Becky Williams (@volcanologist) is near the base of the reworked pale, and a distinct shallow bedding can be seen. However, the bedding is dipping gently towards the east, which might imply deposition from a source to the west. Which is a puzzle, as there are no source volcanoes to the west that are known to erupt such compositions. Hekla’s magmas, for example, have quite different geochemical fingerprints.
Figure 10
I’ll take this opportunity to mention another puzzle: I’ve seen lots of reworked pale ignimbrite, but so far, I’ve not seen an exposure of reworked dark unwelded ignimbrite.
Figure 11
Moving on, there is ample evidence that the ignimbrite was eroded after being deposited. This is not surprising, given that we’ve seen evidence of thicker ice accumulating after ignimbrite emplacement (remember the overlying subglacial basalts). Like the ice currently forming Iceland’s ice caps and valley glaciers, this thicker ice would have been temperate (i.e. wet-based) ice, which is erosive. Much rarer polythermal (cold-based) ice, is much less erosive. A good example of erosion of a welded pale ignimbrite is seen in Figures 11 and 12, which are two views of the same exposure. This exposure also illustrates another notable feature that we see everywhere – the welded ignimbrite is always highly fractured, and not in a regular manner (e.g. columnar fractures). After welding, some unknown process has produced a series of irregular brittle fractures. This exposure permits the following time sequence to be suggested: ignimbrite emplacement, welding, erosion, then sediment deposition, then further erosion (as the sediments are themselves eroded). Interestingly, erosion of the welded ignimbrite occurred before the sediments were deposited, implying a time gap of unknown duration. And a final point – we don’t know what might be missing due to erosion, so the sequence above may be incomplete.
Figure 12
Ignimbrite Varieties
In this brief section, I’ll simply provide a few images of the different varieties of ignimbrite, and point out some of the puzzles to be solved. For me, the biggest and most crucial puzzle is the relationship between dark and pale ignimbrites – are they from the same eruption/source? Are they the same chemical composition, with the different colours related to a physical process (e.g. vesicle sizes/abundance)?
Figure 13
Figure 13 shows part-welded dark ignimbrite, whilst Figure 14 shows a foliated (or sheared) version of the same rock. There is considerable variation in lithics (non-juvenile clasts for the pedants) and in juvenile components (such as pumices), and Figure 15 (60 cm in length) shows a part-welded dark ignimbrite with abundant pumices and lithics, and note that some pale pumices contain lithics.
Figure 14
Figure 15
Figure 16 shows another oddity – a ‘spotted’ ignimbrite containing a mix of pale and dark domains. These are rare and only occur in small pods, and can be either welded or part-welded. Lab analysis would be needed to establish if there are two distinct (geochemical) components. Figure 17 shows a collection of welded to part-welded samples to illustrate just how variable this ignimbrite is.
Figure 16
Figure 17
Finally, we’ve found a few locations where pale and dark varieties are in close proximity. Figure 18 shows part-welded dark and pale ignimbrites in contact, with clearly different pumice contents (i.e. the dark is relatively poor in the white pumice clasts). This image is on top of a small cliff, and so the dark appears to be on top of the pale: if normal stratigraphic rules operate, the dark ignimbrite is younger. Interestingly, the layer immediately above the dark ignimbrite is rich in accretionary lapilli (Figure 19), and was the only good example we found. There are likely to be other exposures.
Figure 18
Figure 19
New evidence overturns an old model
I’m going to describe one bit of evidence that argues against Tindfjallajökull being the source of the Thórsmörk Ignimbrite. (There are other corroborating strands of evidence, but I’ll leave Jonathan Moles to tell the full story.)
Figure 20
The thickest exposure of the ignimbrite (c.200 m) logged in Karl Jørgensen’s 1980 classic paper was underneath a prominent rhyolite lava called Hestur on the lower SE flanks of Tindfjallajökull (Figure 20). This is almost 3 times thicker than any other measured thickness of the ignimbrite, so was I both curious and suspicious.
Figure 21
.
To access the pyroclastic pile requires crossing a fast-flowing knee-thigh deep glacial river (Figure 21), which swells in the afternoon as ice melting increases, which in turn increases adrenalin. The first exposures encountered near the stream lacked the essential components of the ignimbrite (e.g. the expected matrix, pumices, lithics, phenocrysts, etc), and I assumed that I’d encounter the true ignimbrite higher up. But no, all the way up to the lava base the lithology was the same – an impersistently bedded pumice-ash breccia containing occasional fresh obsidian clasts. Apart from a completely different componentry to the Thórsmörk Ignimbrite, this pyroclastic deposit was intruded by lava lobes displaying pervasive small columnar joints (Figure 22), something that I’ve never seen at any true Thórsmörk Ignimbrite locality, and is not reported in the literature. The contact between the pyroclastic pile and the overlying lava is seen in Figure 23, and is often oxidised, which usually indicates near-simultaneous eruption between such rocks (see Figure 20).
Figure 22
Figure 23
So, this is not the Thórsmörk Ignimbrite, and once you remove this abnormally high thickness from the pattern, the argument that Tindfjallajökull is the source weakens dramatically. But what is this pyroclastic deposit? I had the advantage of seeing similar pyroclastic deposits at the Mount Rainier and Öraefajökull volcanoes, where such deposits are found underneath rhyolite and dacite lavas that have flowed along ridges flanked by ice (valley glaciers). These pyroclastic deposits are thicker where there are sudden drops in the ridge, which allows relatively volatile-rich lava in the core of the lava to vesiculate. I’ve not yet published the Öraefajökull work, but the classic paper on ridge-bounded lavas in glacial settings at Mount Rainier is worth a read if you are interested – see Lescinsky & Sisson reference at the end.
Endnote
There’s much more to the Thórsmörk Ignimbrite than I’ve described here, and it remains something of an enigma – hence the title.
What you are getting in this article is an example of fieldwork ‘in the raw’ complete with uncertainties and puzzles. Published papers never reveal the process of reaching the final interpretations and conclusions as there is simply no space (always at a premium). Instead, in published papers you get a more polished version that is designed to be convincing.
You will note a relative lack of interpretation and speculation in this article. This is deliberate as I prefer much more corroborating evidence before suggesting interpretations in public, and we’re not at that stage yet. Of course, I have my ideas of what happened and how the different components are linked, but I’ll leave these in my notebooks for the moment.
So, I hope I’ve given you a bit of insight into a fascinating and accessible enigma. And one in which if you have the interest, you can go and have a look at yourself, as there are daily buses into Thórsmörk throughout the summer and a short walk will take you to some great exposures.
Supplementary Information – background
Prior to 2013, some of the key aspects of the Thórsmörk Ignimbrite within published peer-reviewed papers were:
1. The largest late Pleistocene ignimbrite in Iceland. At least 6 km3 in volume, which equates to 4 km3 DRE (dry rock equivalent = magma).
2. Up to 200 m thick, comprising multiple flow units.
3. Varies from unwelded to welded.
4. Irregularly exposed in valley bottoms in the Thórsmörk area, plus on the lower south-facing flanks of Tindfjallajökull volcano to the north.
5. Depositional environment involved little or no ice.
6. Geochemistry indicates that it’s a rhyolite. (For those who are interested, it’s a comendite, which is a mildly-peralkaline rhyolite.)
7. Tindfjallajökull was the source.
8. This eruption may have created the caldera at Tindfjallajökull.
9. Linked with North Atlantic Ash Zone II (NAAZII) which is a major marine marker horizon dated to c.53-58 ka which is roughly the middle of the last glacial period.
10. Meltout of ice-rafted debris was responsible. Therefore, there was sea ice to the south of Iceland.
11. One of the few ash layers visible in Greenland ice cores. Therefore, the eruption had to have an explosive and far-travelled atmospheric phase in addition to the terrain-hugging PDCs that formed the ignimbrite.
12. The ignimbrite itself has never been convincingly dated.
Subsequent work, largely by PhD student Jonathan Moles (The Open University) has shown:
• Point 2. Incorrect. Removing an incorrectly identified exposure reduces the maximum true thickness to c.70 m.
• Point 7. Tindfjallajökull is not the source.
• Point 8. The so-called caldera at Tindfjallajökull may not exist – no clear field evidence for downfaulting was found, despite good exposure.
Supplementary Information – useful references
Austin et al (2004). J Quaternary Sci, 19, 137-146.
Bramlette and Bradley (1941), USGS prof paper 196.
Jorgensen (1980). J Volcanol Geotherm Res, 8, 7-22.
Jorgensen (1987). Lithos, 20, 153-168.
Ram et al (1996). Geophys Res Letts, 23, 3167-3169
Sigurdsson et al (1998). EOS, 79, p.377.
Mayon said ‘enough’s enough’ and sent PDCs down the S and SW gullies today. Looked to be just before sunset, and lots of cloud cover at the time of the collapse. Therefore, no way to tell if the famous perfect topography changed at all.
‘Massive dome collapse; according to this local report. https://www.philstar.com/nation/2026/05/03/2525249/mayon-slopes-collapse-due-lava-flow#google_vignette
Dramatic video of pyroclastic flows. https://www.youtube.com/watch?v=hvE2jp_2g7w
Really enjoyed that article, i seem to have missed it the first time around. I presume mr mcgarvie has since published a theoretical explanation and an update and expansion is coming?
There is this 2019 open access paper published in Geology: https://doi.org/10.1130/G46004.1
https://www.windy.com/sv/-SO2-tcso2?tcso2,-1.242,25.462,4
A rather impressive sulfur cloud over congo now: maybe the current huge lava lake at Nyiramuragira is getting stronger and more active again ?
https://browser.dataspace.copernicus.eu/?zoom=10&lat=-1.81404&lng=29.17923&themeId=DEFAULT-THEME&visualizationUrl=U2FsdGVkX1%2F4ijrXPy0KTIZ%2BeilQGpGC1nJipyzsY5mRv%2FYnjUX3EJpa93B%2FWUdB7q%2FCBFRUeThQ0AXHJ3PInwBmkkchdvlkit%2Bqc3MnYNqBKCsMvxOd9X%2FOGr7B8wRQ&datasetId=S2_L2A_CDAS&fromTime=2026-04-23T00%3A00%3A00.000Z&toTime=2026-04-23T23%3A59%3A59.999Z&layerId=1_TRUE_COLOR&demSource3D=%22MAPZEN%22&cloudCoverage=30&dateMode=SINGLE
Very gassy and polluted just like Kilauea
https://browser.dataspace.copernicus.eu/?zoom=13&lat=-1.494&lng=29.22071&themeId=DEFAULT-THEME&visualizationUrl=U2FsdGVkX1%2FwKRBLEThoj23sW95C%2B8xZuGv3rfO3jMj%2B6vB%2FqqUINVRxx8USJENjcvlulBp%2BK8P6ICFTbxIjRku%2Bw60hX9ChY%2F8n%2B4c1jCtXCDLvni167TjskST5%2FHWm&datasetId=S2_L2A_CDAS&fromTime=2026-05-03T00%3A00%3A00.000Z&toTime=2026-05-03T23%3A59%3A59.999Z&layerId=1_TRUE_COLOR&demSource3D=%22MAPZEN%22&cloudCoverage=30&dateMode=SINGLE
Nyiragongos lava lake gas plume today
https://browser.dataspace.copernicus.eu/?zoom=14&lat=-1.3912&lng=29.19007&themeId=DEFAULT-THEME&visualizationUrl=U2FsdGVkX1%2BS2%2BcGIQklTk96H%2B9l48fqyt86NQ9dHGBo0i%2FPiNhEE6dysOZ6JhPdS0S5nVJjURvbygRZdQjnrVZi%2B04buDLQ0sYJo%2FkI%2BgpEePjON7SqYWVtrY3TuVQk&datasetId=S2_L2A_CDAS&fromTime=2026-05-03T00%3A00%3A00.000Z&toTime=2026-05-03T23%3A59%3A59.999Z&layerId=1_TRUE_COLOR&demSource3D=%22MAPZEN%22&cloudCoverage=30&dateMode=SINGLE
Nyiramuragiras lava lake plume today
Always so very gassy! highly alkaline lavas have alot of volcanic gas
A wonderful study on Thor’s darkness!
Hekla is a young volcano, Tindfjallajökull is dormant since the rise of Hekla. I’ve thought about whether Tindfjallajökull was a predecessor of Hekla. The magma spectre of predecessor resembles a lot that of Hekla. We know that Hekla sometimes did huge explosive eruptions beyond the typical historical eruptions. The normal eruptions of Hekla begin with an explosive stage, but soon switch to a long effusive stage. But in some cases a “bad” eruption happens that remains explosive throughout the whole period. This applies mainly to the numbered H eruptions of Hekla H-1 to H-5. Maybe Tindafjallajökull did explosive eruptions like this sometimes.
Tindafjallajökull lies more close to Torfajökull than Hekla and Bardarbunga. There are some ridges in the map that link both volcanoes. Did there exist fissures by which Tindafjallajökull could push the “Start” button of Torfajökull? During Holocene Torfajökull only did eruptions by the aid of a different volcano. I imagine that this wasn’t much different during the Weichselian glaciation period (115,000 years to 12,000 years ago).
“magma spectrum” is the correct expression 😉
Tindafjallajökull had a similar magma spectrum as Hekla with both basaltic, intermediate and silicic magmas. Unlike this several big volcanoes of Iceland are bimodal with either basalt or rhyolite and only a mixture of both occasionally. This applies f.e. to Torfajökull, Askja and Krafla.
Barda is getting noisy again along the ring
Its the caldera block moving
Or resisting to move… An M5 is incoming. It missed the opportunity to do a May Day parade, but still has a chance to do a Star Wars Day show. May the 4th be with Bárðarbunga!
The next five days are liberation days across Europe. More chances for the Bard to join in with the celebrations!
Lots of opportunity. Maybe it’s just holding back because it wants to honor its Norse heritage and celebrate Syttende Mai (May 17:th).
looking at the insane number of quakes this time compared to other pre m5.x periods, i wont be surprised if we see a pattern change
This is the first one after IMO switched detection system to SeisComP. It seems to detect a lot more small quakes and also gives many false detections. If you filter out quakes below M0, then it’s on par with several previous events.
If you use skjalftalisa to view older quakes, there are a few things to be aware of. They have added categories to the quakes. QU is quake, EX is explosion, and OT is other. QU is selected by default, which will significantly reduce the number of older quakes returned by the search. Untick it. Then there seems to be a problem with time zone conversion. If I select 00:00 as start time, it returns no results. I suspect it tries to convert the form input from my local time zone (Sweden), to Icelandic time, but gets the subtraction wrong and tries to use a negative hour, which returns no results. Unfortunately, selecting a date from the date picker automatically sets the time to 00:00, so you have to manually set the time to later in the day, then it works. There’s some similar problem with the weekly quake count and some weeks count zero quakes even if there are plenty of them.
Tomas any chances that Bardarbunga can start to behave like Nyiramuragira? same setting just continetal in Africa: you haves a ring fault eruption that makes an open vent. Iceland is after all one of the most powerful magma sources in the inner solar system togther with Hawaii. I read that recent sicence on the astenosphere below Vatnajökull ( 90 km
down ) estimates the mantle
rocks there to be well above + 1600 c perhaps + 1640 c or more thats quite close to
the Hawaiian plume temperature thats estimated to be the same or just marginaly hotter. This is much hotter than previous estimates of the Iceland plume temperature. It makes sense since Iceland is compositionaly identical to Hawaii basalt
I guess the oceanic plate divergent movements in Iceland is much faster than in Virunga and that likley completey prevents constant vents in Iceland. Africa is slower and under even much thicker crust and you gets stranger alkalic magmas
More likey you will see a Galapagos style ring fault or radial eruption there soon
One very big difference is the ice cover. It’s possible that Bárðarbunga does small subglacial eruptions more frequently than we know.
There is a volcano on Io named Surt after Icelands fire giant Surtur. Just a single lava fountain from Surt can last for weeks and cover an area bigger than Iceland with dark basalfic tephra and lava flows can cover many
1000 s of square kilometers in weeks on Io s night – side its an angry glowing spot under a ionized glowing plume
Also Kerkfjöll did more quakes recently.
Stromboli is very active with many lava flows over the Sciara Del Fuoco. The lava looks very fluid like Hawaii because of the steep Sciara. Would it also look fluid in flat landscape? GVP mentions a variety from Picro-Basalt to Trachyandesite as Stromboli’s magmas. How fluid are they usually?
Kilauea is impressive at the moment with both vents overflowing and one blowing domes
Both gps and tilt measurements are at a level where a fountaining event can start. Time to make some popcorn.
The fountain from the north vent in the last episode buried the south vent in tephra. The vent is still open, but the elevation was raised by several meters and it now sits clearly higher than the north vent. I wonder if this somehow changes the dynamic between the vents or if the difference is too small? It obviously has no problem with generating dome fountains at least. Nice looking dome and lava river right now.
Large dome from north vent and flames from the south one. Flashback from the start of the last episode.
The precursor activity seems more vigorous than in the previous episode
After a vigorous overflow from the north vent, now it’s reversed with the south vent overflowing and the north vent quieting down. Once fountaining commences, maybe both vents go off together? Time will tell, but it’s getting close.
Now fire is jumping up! The North Vent is the first to erupt actually.
Looks like it might be starting.
Sorry, false alarm. I’ll just sit and wait now. 😅
don’t let the popcorn go to waste.
I have a feeling they will come in handy soon.
Might be starting now.
The popcorn will only be bought by me when we haves a true specialized Ionian volcano – jupiter orbiter specialy made for Io s enviroment which is possible. Maybe Albert can get Nasa and Musk intrested in Io?
Still Kilauea is by far the most impressive induvidual volcano on Earth: now you haves very nice fluid dome fountains 🙂 again
Yes tilt dropping fast so it have started
Interesting that the drop of the tilt comes before the high fountains
7:30 HST the first signs of the actual eruptions began with rapid escalation.
Yep. There she blows
Looks like it’s starting… North vent overflowing for over 30 minutes now and seems to be increasing in vigor.
Tilt is dropping now too.
Of course it started while I was outside feeding horses 😂
Icelandic horses? They want to keep your attention away from the competition
I think you might be onto something 😂
Yes, they are Icelandic horses. That’s where my interest for Iceland started. Then Holuhraun happened…
I wish we coud get a Halemaumau like vent in Bardarbunga or Grimsvötn but the tectonic rifting likey makes that completey impossible even if technicaly the deep supply in Iceland can do that
In winter of the snow rests easly on their backs without melting then you knows that the horse is well insulated and its not loosing much heat to its sourroundings. Some Yakut Siberian breeds can tollerate – 70 c outside as long as they gets enormous ammounts of food
Their digestion generates enormous ammounts of heat inside their bodies and thats trapped by muscle, fat and fur keeping the horse warm
in severe weather. But extreme cold is suited for siberian breeds
Tomas thats expert can correct If Im wrong about their digestion heating
You’re absolutely right! A lot of their internal heat is generated by bacteria in their gut. If it’s cold outside (below -15°C) it’s better to give them more food than to put on a blanket.
Actually at those temperatures the problem is not only eating. Drinking is near impossible
😂 2006 Memories with past teachers small horse poop crazy daschounds!! they specialy like the ” brown horse balls”during the winter when its frozen and chewy hard
The little dirty sausage dog runns towards a frozen ball and the mouth opens and the little ugly yellow teeth sinks into the horse poop into the prize!
My past teacher = Shouts Drop that horse poop!!!!!
The dog: growl …. grooowl…
My past teacher: drop that horse poop now!!
The solution is simple: the little dog is picked up and the jaws are forced open and a glove goes in … and rips the winter ball out ..
She throws it 10 meters and then the little dog runns after it 🙂 like with football and its repeated again.. the mouth procedure
Thats how they are 🙂
South vent is trying hard to join in, but so far it’s struggling.
V1cam is being pelted
V1 appears to be out of commission already.
Thanks. I can’t access V1 through the USGS Kilauea website, but I can through Google.
North vent seems to be on the wane already? Still a nice show, though.
South vent looks dormant. Rats.
Was hoping for a double header, but the second game got cancelled.
E44 to E46 were only half episodes compared to the predecessors:
Earthquakes continue in the area around the old Halema’uma’u crater.
An assumption (not *the* assumption) is that the eruption is trending toward steady-state and away from episodes.
Yes, this is also my thought. Pu’u O’o switched to the steady effusive lava channel & tube style with the 48th episode. Although the eruption locations are different, it may turn out, that Kilauea’s summit eruption will accidentally also change significantly around the 48th episode.
Here is GVP’s description of the steady eruption of Pu’u O’o beginning in summer 1986: https://volcano.si.edu/volcano.cfm?vn=332010#bgvn_198608
They observed: “Lava shield continues to grow … By mid-September, the shield had grown to 1.5 km in diameter and 41 m high.”
Still lots of earthquakes under the south rim of Halemaumau
Yes! But only one since the end of the episode – so far. I don’t know whether the unrest at the rim is related to weaker episodes.
Could the earthquakes be due to collapsing/disintegration of shallow magma reservoirs/sill under the south rim of Halemaumau? That could explain the lower total flows with the last three episodes…less storage area. With both vents open, as long as the main conduit stays intact, the episodes will continue..but with what volume?
2008 the lava lake eruption was preceded by explosive events. It is possible that there occurs an explosive interaction between a new dyke of lava and the 2020-2026 lava layers above the 2018 created depression.
Although much gas is now released by heavy fumaroles and the twin cones, there will likely still be enough gas in the intruding magma to do explosive things. This type of magma is more degassed, but not completely. It has a different physical behaviour than the early gasrich magma of Dec 2024 to May 2026.
These are photos of an ash plume 2009:
We can’t exclude that the tephra of the early 19th century also came from voluminous ash plumes like this. I imagine f.e. that the ground above a dyke collapses and causes a voluminous ash eruption that exceeds the 2008-2009 ash plumes.
In the absence of on-line gps measurements in the area, it is hard to know. OUTL is going down, in agreement with magma depletion. But the cross-caldera distance is increasing, which can come from magma moving up (to the surface, in fact). The episodes are currently weaker than before and the fountain not as high. Is that due to reducing magma supply, or the vents are becoming too high?
I was wondering whether the weaker, single-vent episodes of late could be because of the elevation difference between the vents, inhibiting south from actually getting going and the accompanying greater volume then able to erupt. As we’ve seen, south is very much a cone builder rather than an effuser like north (not to mention that, aside from the early episodes, south never had a prominent gap in the cone like north still does), so the vent elevation difference episode-to-episode grows as time goes on. North solos then correct the difference for long enough, while still being noticeably lower than south, for another two or three concerted episodes before it needed to be fixed again. North is, due to these three solos already, slowly getting to a higher elevation and south already looked healthier to me as E46 progressed than at similar times during E44 and E45, so maybe – just maybe – south will join the party again for E47.
As for magma supply, the net deficit at the summit sat at 54.5 µrad (about 20.1 million m³) when E46 ended (and at 38.9 µrad at the start), which seems like a rounding error to me for both of Kilauea’s chambers. Despite the frequent swarms almost invariably causing deflation, the average recharge rate still usually sits above 5 m³/s, taking into account the 1 to 1½ m³/s or so suppression of the average at least from these deflation periods, eyeballing the episodes before and after E39. I therefore don’t think magma supply is an issue and probably won’t be for a good amount of time still.
I’d assume that half of the magma is searching and building a new path towards the surface. The onset of a steady continuous eruption style like Kupaianaha 1986 will likely begin on a new location at a new vent. Maybe north of the (broken) B2 webcam.
In September 2023 was a fissure eruption in Halema’uma’u and the down-dropped block. Does the pathway that magma used for this eruption, still exist? Can new magma use this path again?
The Video about the September 2023 eruption (it lasted six days) shows that it was a pure fissure eruption that didn’t concentrate on a central vent:
https://www.youtube.com/watch?v=utQJcz6lE8U
1983 the first episode of Pu’u O’o in January also was a pure fissure eruption without a central vent yet. The actual Pu’u O’o cone rose in summer 1983. Was the September 2023 eruption a predecessor for the 2024-2026 episodic eruption as the January 1983 episode was one for the later Pu’u O’o development? If this is true, then it seems possible that Kilauea’s summit activity once will return to the location of September 2023.
I don’t think that pathway still exists, because even during E1 of the current eruption, there was no activity whatsoever there. What did “erupt” from near the vents following several episodes, was merely old stuff pushed out due to the weight of the lava flow on top of the still-liquid 2020-2023 interior of the Halema’uma’u crater, thus only superficial. It’s also of note that September eruption happened on the connector between the Halema’uma’u chamber and Kilauea Iki (HVO said it was the first summit eruption outside the crater since the 80s or so), while the current eruption couldn’t be further away from it, on top of originating from the Halema’uma’u chamber itself.
If a new vent were to open, I’d expect it to be on the ring fault (analogous to E30), as the eruption is located, and initially opened, on it, not on a fault passing linearly through the caldera. Perhaps adding even more to the unlikeliness of the eruption ever reoccupying the September fault, is that this E30 fissure never showed any subsequent activity, a true one-and-done. If even two or three weeks are enough to shut down a ring fault pathway close to the vents, then surely the September 2023 fissure must not be an option anymore.
Albert magma supply will NEVER be an issue for Kilauea as long as the vents and pipes upwards to surface are stable. Kilauea maybe a gentle volcano but it acually haves the fastest deep supply of any known individual volcano on land or on Earth, ironicaly this superfast supply is what makes the eruptions so gentle and fluid and hot way too fast for evolved stale magmas. Kilaueas magma supply is correctly probaly equal to many hundreds of perhaps many thousands of cascade volcanoes put togther into one single magma channel! and probaly equal to a majority of Icelands deep magma input but crammed into one single magma conduit. At Kilaueas resupplt rate you can form whole magma chamber complexes in just a few years something very few volcanoes can do
True on average, but the supply varies a lot from year to year. The rate of J.O of 5m3/s is about 0.15 km3/yr which is at the upper end of what Kilauea does. Averaged over time, eruption rates vary between 0.01 and 0.1km3/yr. The low value was before 1950 when Mauna Loa was more active. The supply rate into the shallow magma reservoirs varies more. After a major eruption it is high (as the shallow magma reservoir is low in pressure, so magma rises easily). As the shallow reservoir fills, the supply rate goes down as an exponential decay, e^-ct. I have not checked whether the eruption rate over the past month follows an exponential decay – there are quite a few variables that affect it so it may not be obvious. For Bardarbunga 2014/15, the eruption rate followed this decay very closely.
Halemaumau filling now is very similar to Io a crater thats filling up with lava, you can see Kilaueas caldera as maybe a kind of patera even if Ionian paterae maybe also result of hot sillicate lavas eating through layer pancakes of sulfur glaciers and basalt flows on the moons surface. But Im pretty certain that some Ionian volcanic craters are purely result of sillicate lava withdrawl ( Ionian magma chambers arer far larger than Earths ).
Scale Halemaumau up to 150 kilometers and to max 300 kilometers and you gets a large Ionian volcanic center ( dark sillicate lava ) thats how huge these volcanoes are there. Toba is a feature on same scale but its explosive cold magma
And on Io it coud be 100 s of m3 perhaps 1000 s m3 in huge circulating lava lakes if magma moves between chambers in the Ionian crust.
Ionian constant surface lava flows at supply rate maybe feed at 50 m3 per second as a constant or a 100 m3 per second, some flow fields confirmed to be 40m3 per second. The pahoehoe , (effusion rate) of the Amirani lava flow field on Io is generally estimated to be perhaps 50m3 of basalt/ komatite per second for decades ( still ongoing )
For huge lava seas on Io Loki Patera here the total volume of magma moving through the system is estimated at approximately 100 km³ per year. This converts to an average supply rate of about 3,170 m³/s.
Thats saied Kilauea is quite a monster with a few cubic meters a second making Kilauea perhaps equal in strenght to a small Ionian volcano?
The huge complexes of seas of lava near Ios south pole probaly dwarfs Loki Patera in supply rate ( lava moving through the lakes ) monster volcanoes is a good definition here! https://www.jpl.nasa.gov/news/nasa-juno-mission-spots-most-powerful-volcanic-activity-on-io-to-date/
Im very much a volcano addict but only the largest volcanoes really attracts me on Earth Grimsvötn, Kilauea, Mauna Loa, Bardarbunga and Nyiramuragira are quite massive indeed but quite very compared to Io s volcanoes. I hopes we gets more probes soon enough. I woud like to see Ra patera and Pele Patera photographed upclose
Im very much a volcano addict but only the largest volcanoes really attracts me on Earth Grimsvötn, Kilauea, Mauna Loa, Bardarbunga and Nyiramuragira are quite massive indeed but quite very small compared to Io s volcanoes. I hopes we gets more probes soon enough. I woud like to see Ra patera and Pele Patera photographed upclose. There is a few probes in planning stages for Io but they have not been built or building yet.
Titan Dragonfly will also be very fun even if its not the stuff Im looking for
Not an easy place to visit. The strength of Jupiter’s gravity is a problem: to get into orbit around Io, you need to shed a lot of velocity from the infall towards Jupiter, and space mission work with minimum fuel. We have a similar problem with Mercury: it takes years to nudge a craft into orbit there. BepiColombo was launched in 2018, made its first Mercury flyby in 2021 but needed four more flybys to shed enough velocity. It will go into orbit in November this year, five years after the first flyby. Io is not as bad but it will take time. And that is the second problem: the radiation environment is extreme. The spacecraft and specially the instrumentation needs yo survive during that time. The electronics needs to be radiation-hardened to an extreme degree.
Io is hard to visit but very possible the technologyu already exists. Maybe someone like Elon Musk coud get intrested ome day? the most powerful hot volcanoes in the solar system is irresitible really for me, Io just as iresistible for me and some friends at Nasa as horse manure is for a little dog 🙂
The Juice mission is on its way to Ganymede. At the moment it is still picking ups speed in the inner solar system with Venus and Earth flybys. Once at Jupiter (2031) it will take 3 years to get into orbit around Ganymede. It won’t visit Io but will look at Europa. Io is too hard at the moment. A bigger rocket will help but only a little. The best way to to improve things is by not launching from Earth. We are wasting too much fuel just getting off the ground.
Mauna Loa has significant inflation now:
In November we observed a negative trend, when the current Kilauea eruption had a peak of activity. Since Mid April 2026 strong inflation is back. After the past “Humuʻula Saddle” eruptions it took 3.5 to 6 years until the next eruption followed. If Mauna Loa after the “Humuʻula Saddle” eruption 2022 repeats this behaviour, we get a time frame of 2026 to 2028. In each of the first three Humuʻula Saddle eruptions the following eruption was a summit eruption. The shortest of them lasted for >27 days 1849. This eruption was very weak, probably mainly a gas & steam eruption.
https://www.flickr.com/photos/kevinmgill/54284102007¨
Maasaw patera shield volcano on Io
Looks like Maasaw Patera ( to the right ) experienced a major lava lake overflow between the date these two voyager images when they where taken. Dark basaltic lava flows flowed in all directions! or it coud be ring fault eruptions along the patera pit. But this really looks like one giant lava lake that rose and overflowed its edges. This is a pehnomena thats been seen one some of the larger ionian pateras too like daedalus patera
Ops link wont show maybe I will write a VC post on it later
Stromboli clip with the lava delta visible in the first seconds: https://www.lastampa.it/cronaca/2026/05/06/video/stromboli_in_eruzione_la_lava_scende_dalla_sciara_del_fuoco_e_arriva_in_mare-15611139/
OT: nice NASA satellite image of Shivelyuch with pyroclastic flow deposits on its flank:
Full NASA article with more details here:
https://science.nasa.gov/earth/earth-observatory/melting-snow-off-shivelyuch/
Could iceland pls get going already…these waiting games are killing me.
As requested, we have ordered some activity at Greip. Earthquake swarm on-going – ok, mini ones only but you have to start somewhere.
If you haven’t heard about Greip, see this post
https://www.volcanocafe.org/greip-gjalps-mysterious-sister/
The Met office always mentions this area when talking about eqs linked to bardarbunga’s inflow. I also vaguely remember reading that Bardarbungas deeper magmatic system is thought to be offset to the east from the caldera. Have there been any more in-depth scientific updates on that area?
Not as far as I know! Of course its name is purely for VC-use only.
Between the westend of Reykjanes peninsula and Eldey (Geirfugladrangur) earthquake activity has increased including small swarms: https://en.vedur.is/earthquakes-and-volcanism/earthquakes/reykjanesridge/#view=map
https://everydayoriginal.com/product/outpost-on-io/
Nice artwork! the Io prison if anyone is curious excellent prison camp colony for the solar systems most dangerous criminals ( with the radiation killing first )
https://www.bbc.co.uk/news/live/c0k2g11j2plt
Visiting a “grey volcano”is not a good idea they made the same misstake as Maurice and Katia Krafft
It was an organised tour. You wonder who the organisers were and why they ignored the restrictions that were in place
Its their livelihood?
No social services and free health service there.
True for the porters and guides but the organisers may be different. But they may indeed have arranged the trip themselves
looks like 2 people might still be on the mountain given the article says 20 on the mountain, 15 off the mountain 3 dead
https://www.theguardian.com/world/2026/may/08/hikers-dead-missing-eruption-indonesia-mount-dukono-volcano
Correct. The news says that the two are porters who are helping with the rescue and recovery operations
The article mentions a Rhyolite Lava Flow. How common are they on the longrun for Iceland? They are rare in the world, but Iceland has Rhyolite magma in some volcanoes. Does the geology of Iceland make it easier for Rhyolite to erupt effusively than subduction zone volcanoes?
They are very rare. Rhyolite lava flows require a cool magma that is pure rhyolite to begin with. Starts with magma chamber that slowly solidified, leaving a pure rhyolite for the last part. Now reheat the rhyolite a little bit so it melts and rises but the rest does not melt. There you have your rhyolite lava.
What role does the gas content of rhyolite magma have? Gasrich magma is usually more explosive than gaspoor magma.
Torfajökull has a great and very active hydrothermal system. Is is Iceland’s greatest hydrothermal area with 150km². Does this indicate that the rhyolite magma is strongly degassing? Yellowstone’s past eruptions released voluminous rhyolite lava flows, likely after a period of longterm degassing rhyolite magma. “Approximately 2,000 fumaroles are found within Yellowstone” https://www.nps.gov/articles/000/fumaroles.htm?utm_source=article&utm_medium=website&utm_campaign=experience_more&utm_content=small
The Catalogue of Icelandic Volcanoes mentions rhyolite lava flows of Torfajökull:
“At least eight eruptions have occurred within the central volcano in Holocene time, producing rhyolitic or mixed lava flows (the largest one 0.3-0.4 km3). Four of these eruptions also produced tephra layers in explosive plinian opening phases, the largest about 0.4 km3 (bulk volume).”
https://icelandicvolcanos.is/?volcano=TOR
If rhyolite is remelted after solidification, it will be gas-poor. However, the upper layers of the ground are often saturated with water in Iceland, and this can cause explosive eruptions. The hydrothermal system indicates a stable circulation of water heated at depth. But I think there is not a lot of sulfur emission from Torfajokull (mainly because it is never mentioned). The gas probably is just heated water and not gas coming from magma. I think it is quite a stable, mature system without injection of fresh basaltic magma.
I remember to have watched a video with a Rhyolite lava flow. I have forgotten, on what website it was. The flow looked like a glacier composed of hot rock. It is slow, but also very massive. Very interesting.
YVO describes well the Rhyolite lava flows of Yellowstone. The last one occured 70,000 years ago: https://www.usgs.gov/observatories/yvo/news/rock-glass-and-flowbands-yellowstones-rhyolite-anatomy
?itok=PewRKZ6s
This photo shows a 111,000 years old Rhyolite lava flow that had a volume of 41 km³ (9 times the volume of Pu’u O’o):
I tried to use AI just now to get the latest on the Mayon Volcano, but youtube is full of mostly hype and maybe 10% (at the most) accurate information. Are we still facing possible flank collapse?
Maybe if the plug of degassed lava at the summit becomes oversteepened, we could see a PDC larger than what has occurred so far. As for a St. Helens-type sector collapse, highly doubtful. Mayon doesn’t do offsets from the main conduit; that’s what makes it so symmetrical.
There was a series of dome collapses on May 2 along with the peak of the current eruption sequence.
Also read of some inflation on the northern flank, but there has been slight deflation noted.
Other than an old VC article by Carl (2013) who speculated about a flank collapse on Mayon, I’ve heard of no other credible reports.
UWD with fast inflation now. On 6th to 7th May with convex inflation, while after the previous episode on 24th April inflation had a concave curve. It happens at a time, when the earthquake activity in the summit region has calmed down. Maybe the unrest in this region has stopped and pressure returns to the twin vents:
Another vivid dream I had yesterday afternoon while half asleep: walking Io s surface! walking right up to the hot lava flow fronts at Amirani pahoehoe field ( thats still active confirmed by Juno ) the lava behaved was very much like my Puu Oo hikes .. just hotter and even more fluid
( white hot when breaking out from skinn ) and the thin lava sheets flowing out where many 10 s of meters wide .. long .. but only a few couple of decimeters high
New post is up! It lives!
https://www.volcanocafe.org/grindavik-lives/