A whole volcano tourist mega tour of São Miguel Island

Part 1

São Miguel the ”Green Island” famous for its green subtropical beauty. As dead as it looks, it is as alive as any active volcanic island can be between eruptions.

Introduction to São Miguel

After writing my Ionian articles (there will be more Io later, since after all it has the solar system’s most magnificent active volcanoes) I felt it is time to return to Earth again, to a much smaller scale volcanism which we can visit in person. The Azores is a magnificent and magically beautiful volcanic island group, consisting of nine emerald green small islands in the mild subtropical northern Atlantic, which I had the luck to visit many times. The islands are Flores and Corvo to the west; Graciosa, Terceira, São Jorge, Pico, and Faial in the centre; and São Miguel, Santa Maria, and the Formigas islets to the east. (Click on the link for a map.) While none of these islands are particularly powerful in volcanic vigour, say compared to the giants of Hawaii and Iceland, the Azores have much much more volcanic geo-variation than most other volcanic islands (the Canaries have a huge variation too). The Azores also sit in an even much more complicated geological setting, dominated by tectonic faults and slow spreading ”transform ridges” that are associated with the triple junction point in the Atlantic ridge.

The Azores have many volcanic features that ranges from evolved explosive calderas to highly primitive monogenetic fissural vents to even stranges alkaline basaltic ”pahoehoe low silica stratovolcanoes” (think of Pico Island ). The magmas you find in the Azores are alkaline but a bit less so than in the Canaries. They range from very fluid alkaline olivine basalt to Etna-like trachybasalt and the evolved calderas produces highly evolved trachytic magma.

The Azores as a region is huge. It is a submarine lava platform with nine islands which have emerged on leaky faults. Eruptions in the whole region happen on average every 20 years. Most eruptions are likely submarine and few break the surface. Volcanic activity is much less frequent on the individual islands where often many 100 years go between the eruptions leaving almost no bare lava flows on the islands. The last surface eruption happened in 1957 at Caphelinos in Faial where an infant island grew out the sea and merged with the island. Eruptions are slightly more common among the western islands near Pico where the magmatic source is thought to be. The last submarine eruption was in year 1998 – 2000 at the Serreta ridge at Teceira Island. All islands except Santa Maria are active: there is no age progression like Hawaii and Galapagos.

Geologists have debated a lot why the islands exist in the first place. Its true that leaky seafloor fault tectonics explains their locations on long lines that follow faults. But the seafloor crust is swollen and thickened in the Azores region, a clear sign of increased melting productivity and heat flow. It is generally called the ”Azores Hotspot” with indication for a large region with higher temperatures in the upper mantle, but it is a weak hot spot compared to Iceland and Hawaii. The Azores hotspot seems to be past its peak. The construction of the submarine lava plateau was in the Miocene, 20 million years ago. Lava productivity since then has not been enough to raise everything above sea level and form a ”subtropical Iceland” or say an imaginary ”Atlantis”. It seems clear that magma productivity has slowed since Miocene but the hotspot remains fairly active as a whole region. The Azores hotspot is sizable having an impact on a large seafloor area but it is not a very intense hotspot, and certainly not so at São Miguel. Most of the remaining heat seems to be around Pico Island that has had long lived low intensity eruptions in the past.

In the Azores you can see whales, green fields, dive with manta rays, hike subtropical forests, see lava tubes, crater lakes, cinder cones, calderas, hot springs, old lava deltas, pyroclastic deposits, but in very green shades. The nature greenery, mild oceanic subtropical climate and dramatic landscapes draw a lot of tourists to the Azores for hiking and photography, so I thought to write about São Miguel which is the largest and most frequently visited of all Azores islands, and many may visit without knowing its an active volcanic area. As told, I had the good luck to visit a few times, so that is why I wanted to write about it. The volcanoes there, while visited by many, are also perhaps overlooked and ignored so this gives another reason to write. Lushly overgrown green silent volcanoes can be just as beautiful as the burned stark landscapes of other highly active volcanoes. Azores offers lots of scenery and São Miguel offers some of the most scenic volcanic sights in the archipelago. The calderas of Sete Cidades and Furnas have some of the top scenery in the whole archipelago, only rivaled by hiking the summit of the Pico volcano. The volcanoes on São Miguel are also the most directly accessible in the archipelago as you simply can fly there directly. Getting to Pico can be more complicated if you start your trip outside Portugal.

I had the luck to visit São Miguel Island just a few years ago, quite recently, and I liked it a lot. It is very beautiful and relaxing. When you land there you are immediately greeted by Ponta Delgada’s stunning architecture with white plastered facades and street stones which contrast strongly with black, alkali basalt windows and facade frames. It is the same with their cobbled streets where white and the black lava slabs are joined to form interesting pattern shapes. The alkaline basalt seemed so black it is almost as it was sploshed with hoses that spewed a jetblack color. In some cobble stones pale green olivine grains were seen. I don’t remember hawaiian basalt being this black. The whole city is full of cozy little streets, that are too narrow for cars. Small shops and restaurants are everywhere, and some museums too. I myself loathe the crowded, noisy mainland, so the Azores suits me very well, there you are away from it all. The locals live a peaceful and relaxed life that has been pastoral for many hundreds of years. The locals seemed healthy and happy and foods were unprocessed and of high quality. Life on the island is very slow and there seems to be little to be bothered about, there is almost no crime and communities outside the main city almost feel like everyone knows everyone. I liked it a lot getting away from the noisy mainland to a place of calm and mental relaxation in the middle of nowhere. For many 100 s of years many communities on this small island were more or less completely isolated from each other. The invention of cars and an effective road network linked everything together and today São Miguel has one of the best road networks of any volcanic islands. A rental car is a must have if you want to do the whole volcano tour that I suggest in this series.

Despite the peaceful life, natural volcanic beauty and fabulous climate that São Miguel offers, it is very surprising that this green island and the other Azores islands have not been completely commercially exploited and turned into touristic megapolises like Atlantic versions of Hong Kong. And that is something we should be happy about, that it has not happened yet. The Azores have only recently being discovered by global tourism.

It is important to remember that São Miguel is not a ”wild paradise” like Kilauea’s wild forests, here the landscapes are highly altered by human activity. The island resembles a wild but well managed garden and somehow it works very well as a tourist attraction and many parts of the Island are still very primordial looking, despite heavy human modification to the landscapes. The original laurel subtropical forests are only found in isolated river valleys and volcanic highlands.

The weather also suited me well: The Azores is an oceanic subtropical climate so the most pleasant type of all. Such climates are rare, existing only in isolated islands in the large oceans at latitude 30 s, its always mild and pleasant, never hot, never cold, no extreme temperatures and remaining quite warm all year around. The mild daytime temperatures outside range from 16 C to 24C depending on season with sky high humidity and results in lush greenery growing everywhere. The sea remains quite warm all year around and in late summer it may just get swimmable enough, but it is not in any way as warm as more tropical waters further south. It is often very cloudy and rainy all year around and that makes Saõ Miguel a very green place for sure. The climate is perfect for agriculture and gardening, turning the entire Island into a ”Shrek slime swamp green” salad bowl.

This kind of weather is excellent for hiking. In many other volcanic islands that are closer to the equator it gets too warm for doing such activities. Hiking has become the main tourist activity here because of the mild climate. Strong green nuances are everywhere. There seemed to be no limit of the types of plants and trees that grew when I was there. The strong greens and clear blue subtropical ocean contrast strongly with black alkali basalt sea cliffs, makes an attractive photography scene. The same is of course with everything on the island. Gardens, green crop fields, pastures, forest plantations and parks are everywhere so there are few signs of volcanic activity at first glance. But when you explore the surroundings its volcanic nature becomes apparent. Grassy cinder cones rise above rooftops and huge water filled calderas dot the island. Lava tubes that have been turned into cave museums can also be found under the main city.

Gruta do Carvão is a nice lava tube in Ponta Delgada, highly recommended to visit and offers lava flows structures such as drips, stalactites and shark teeth structures, as finely preserved as in any hawaiian lava tube. It is likely the best starting point, before getting out on the roads for a week long geological road trip. That one was the first stop I did during my visits there.

São Miguel is tiny compared to Iceland and Hawaii but it is large enough that there is enough to see for a whole week of visit by road trip. In this article series, I want to show that even weakly active volcanic areas can have beautiful landscapes and have very complicated fascinating geology. Hiking and geo tourism have increased a lot in São Miguel in the last three decades and have together with geothermal energy brought profit and increase in living standards. Without this, the island would perhaps be an isolated and forgotten place.

Saõ Miguel may have weak volcanism but it is surprisingly varied in composition and eruption deposits for being so small. The island spans almost all types of eruptions possible, raging from hawaiian to plinian. It has the whole volcanic package of types of volcanic tephra and constructive edifice products ranging from hawaiian style spatter cones and strombolian cinder cones to explosive evolved pumice cones and domes. Almost all types of tephra and tephra deposits can be found too on São Miguel, ranging from mafic scoria and spatter to evolved ignimbrite deposits. There are very few other volcanic islands that offers such geomorphological variation in such a small area. The volcanoes themselves are also just as varied as the island is, with every central volcano hosting almost all kinds of possible volcanic landforms, ranging from scoria cones to trachytic domes. In short, a central volcano like Sete Cidades can produce almost any kind of eruption due to its bimodal behaviour. I have also noticed the lack of basaltic drainout calderas at São Miguel, indeed no real polygenetic shield volcanoes can be found here. The eroded Nordeste volcano may be a counter example but it was not a traditional shield volcano in terms of what can be found in Iceland and Hawaii. That is probably because magmatic supply is so very slow, large magma chambers quickly get stale and turn to trachyte (a mildly alkaline ryholite) without a rapid supply influx.

In São Miguel slow magma influx results in dangerous central stratovolcanoes that resemble Andean volcanoes more than anything in a mid-ocean ridge, which is fascinating. Furnas, Auga De Pau and Sete Cidades are the most dangerous volcanoes on the island with the top  would-be ”killer” Furnas.

Photo: David Wallance, a secret ”Gollum pool” on São Miguel, never underestimate an active volcano…they can look as dead as stone yet still be alive. These mysterious jungle pools are quite common in Azores and gives it a spooky and enchanted feel. 

The island seems to consist of 7 volcanic zones, Nordeste, Povacao, Furnas, Congro Fissural, Agua De Pau, Picos fissural zone and Sete Cidades (or 6 if Congro Fissural belongs to Furnas). Of these, five are well developed central stratovolcanoes that host silicic trachytic magma chambers and three of these beasts are very dangerous as populations live very close to and even inside them! Any large explosive eruption would be catastrophic. The most common terminology for São Miguel is 6 volcanic zones but I have my own ideas how the volcanoes should be grouped. The borders between them can be quite diffuse visually and especially so between Picos fissural system and Sete Cidades which merge smoothly into each other without clear borders.

São Miguels volcanic complexes, which have emerged and merged over geological time to form the island are a plio-pleistocene formation. The older parts of the island are around 4 million years old while the younger western parts of the island are just a few 10 000 s of years old and many recent eruption landforms are just thousands to a few hundreds of years old. The western parts of this island are the youngest while the eastern is the oldest. São Miguel looks a lot more youthful than Madeira to the south yet is also far older looking than Pico to the west which is even more youthful.

São Miguel’s elongated shape comes from volcanoes growing on ”leaky” faults on the sea floor that is operated by the triple junction tectonic boundary. The island is run through by faults. The western parts of it act like an ultraslow spreading ridge while the eastern part is faulting and a little spreading. It is very complicated. Sete Cidades in the western parts sits the easternmost extent of the Hirondelle basin and obtains its magma from it. The island didn’t take on its modern shape until about 50 000  – 40 000 years ago when an eruption of land-forming lava joined the eastern and western volcanic massifs between Sete Cidades and Picos fissural systems to form the youngest volcanoes on the island.

Volcanism on São Miguel is infrequent and can be called ” weak” compared to the more major hotspots elsewhere but it remains fairly active at least over longer timescales. Since colonization in 1452 there have been reported eruptions (most of these been shallow submarine ) in 1439, 1538 two times in 1563 then in 1564, 1638, 1630, 1652, 1682, 1713, 1811, 1911 The only major explosive eruptions on land are 1563 and 1630, each as large as St Helens 1980. 1652 was the last mafic lava eruption on land. Many historical reports are uncertain and may have confused phreatic blasts with eruptions. On land in São Miguel the confirmed historical eruptions have happened 1439, 1563, 1630 and 1652. Submarine eruptions just south of the island happened in 1907 and 1911 and broke submarine cables. The last underwater eruption anywhere close to so São Miguel happened in 1981 at Fractura Mónaco system.

In the last 5000 years, there have been 36 monogenetic cone forming mafic events on the island. Eruptions from the evolved central volcanoes on the island form pyroclastic eruptions and pumice cones and trachyte domes in the calderas, while the flanks and monogenetic fields produce mostly hawaiian and strombolian eruptions of highly fluid alkali basalt, forming cinder cones, scoria cones and maars. The magmas of São Miguel are hawaiites, alkali basalts, ankaramites, mugearites, benmoreites and trachytes. The base un-evolved magma is mild alkali basalt. They are alkalic but quite mildly so compared to Nyiragongo. The eruption lavas temperatures on the island range from 820C to almost 1200C depending on composition, and how fast the magma rose. The viscosity ranges from likely nearly as fluid as Hawaii for low silica alkaline basalt to somewhat more viscous than Popocatépetl for a round trachytic dome. São Miguel mafic parent magmas like most alkaline magmas are more gas rich than subalkaline thoelitic magmas and that shows at every vent: green-draped cinder cones can be found everywhere here, as is the case with the Azores and all other alkaline islands. The lava is gas rich and fountains get taller than in Kilauea and Iceland forming more cooler fragmentation and building up scoria piles.

The next eruption in São Miguel is very likely to be submarine close to the coast where such eruptions form monogenetic tuff islands or plumes of discoloured hot seawater. An eruption on land in our lifetime is possible but not certain and would be most likely in the young western parts of the island, like at Pico’s volcanic fields. That scenario would resemble the 1971 La Palma eruption. Previous eras of higher activity hundreds of years ago may have seen two eruptions during a human lifetime. The silicic central volcanoes Furnas and Sete Cidades are also fairly active over millennia timescales and any eruption in these will not be good for the caldera residents. Doing some simple maths on São Miguel’s eruptions including all its volcanoes indicates an eruption once a century or more but that figure is just math. The island can have dormancy times lasting 100 s of years but it is much more active than Tristan da Cunha and most of the Cape Verde islands. Volcanoes are not machines: they don’t have any timetables at all, but going on previous eruptions, one can assume or speculate that the island is due for an eruption in the not too distant future, perhaps in our lifetime.

After speaking briefly about São Miguel in general, in the next post I will now tour the volcanoes. I thought this post could be good for anyone visiting São Miguel so I am writing a tourist volcanological tour on it. São Miguel hardly provides the intense volcanism of Hawaii and Iceland in terms of fresh lava landscapes, but the island is very beautiful where volcanic features can be examined in a green framework and outcrops and sea cliffs provide good geology. Magma supply to the island is not a lot compared to major hotspots like Hawaii, and Iceland and Reunion absolutely dwarfs it too. The magmatic influx is still enough to keep the islands active as seen but the geothermal features and geothermal power that has been invested in.

In this two part article series we will tour the volcanoes of Saõ Miguel island traveling east to west and stopping at the main volcanic zones and central volcanoes. In real life this article series is meant to be read in a rental car that allows you to do just the same thing as we will talk about in part two. Many persons visit Saõ Miguel every year and likely quite a few of them may not know its an active volcano on the first day they arrive.

To be continued

Literature sources: https://www.amazon.com/Volcanic-Geology-Archipelago-Geological-Society/dp/1862397317

Jesper Sandberg, July 2024

121 thoughts on “A whole volcano tourist mega tour of São Miguel Island

  1. Thank you, Jesper, I very much enjoyed your article about São Miguel. I have been on Terceira several times, and your descriptions of the vegetation topography, etc. is what I saw during my trips. You might have not seen the hydrangea in bloom (early to mid-summer), but the vast swaths of blue flowers are stunning. Recent volcanism is demonstrated across the island by features such as the barren lava-flow outcrops at Biscoitos, a beautiful little tuff cone on the coastal cliffs next to the main city, and sulfurous fumaroles atop the uplands stratovolcanoes. Thanks for the memories, I look forward to your next installment. Steve

    • Teceira is a beautyful island. The Santa Barbara and Pico Alto Volcanic Complexes have lots lots of pancake domes and blocky flows of trachytic peralkaline comenditic ryolites, there is blocky lava everywhere there is probaly a very large evolved magma body sitting in the teceira rift, earlier calderas and igmigbrites are good proof of that. Rifting events at Santa Barbara can throw out long lines of comenditic pancake lava domes. Knowing there is large ammounts of evolved magmas at depth there maybe a large caldera formimg event sometime in the far future. The collapse of the Cinco Picos Caldera is likey one of the larger explosive collapses in Azorian geological history, its still visible after 300 000 years, there been numerous several ignimbrite-producing eruptions after that too.. but something small scale basaltic like serreta or small scale sillic like 1700 s are much more likey in human timescales than a catastrophic huge ignimbrite making eruption that covers everything

      • The one place that impressed me the most in Terceira is Algar do Carvão.

        Didn’t expect to go down an extinct vent of volcano.

    • Same here.

      Been there once, and want to return again (esp. not during winter). Also appreciated the sizes of calderas and youthful Pico. It certainly doesn’t feel “weak hotspot” – the Azores plateau is almost as big as Shatsky Rise.

      Capelinhos site is definitely worth visiting too, suddenly very different landscape. They will even try to explain to you that Surtseyan eruption should really be called Capelihnan, given it happen decade earlier.

      I am looking forward to the next installation of your article.

      • Thats Pico and thats where the hotspot is focused today Pico is the youngest of all islands there even if Azores generaly does not have an island age chain progression like Hawaii. It does looks like Picos upper edifice parts are basicaly a rare type of pahoehoe – stratovolcano, like a giant hornito a bit.. entrail like pahoehoe drapes the entire upper parts of that stratovolcano. It must have had effusive shield building phases where it erupted for 100 s of years at a slower pace than Puu Oo there must have been small lava ponds in its summit feeding lava tubes, it was the lighthouse of the atlantic during its long phases of slow activity. The last time there was souch persistent activity there was a few 1000 years ago. That requires some heat influx to keep that running for long times so its logical to assume that the hotspot haves its focus there. Azores plateau is large but its downright tiny compared to the immense mass that is Iceland Plateau in terms of lava volumes.

        At São Miguel the magmatic vigour have always been very weak and seems to have not been any ”shield” like phases that have been on Pico.

    • Good place for hiking and geotourism in terms of weather its better than Iceland and Hawaii in those terms, its possible to do alot of stuff without getting bothered by strong heat or windy cool conditions. Its amazing that souch a small place have souch volcanic variation, Sâo Miguel is therefore one of the main study sites for geology students from Scandinavia and other areas.. lots of field trips to this place. While an eruption wont happen tomorrow its entirely possible that it coud erupt in our lifetime and frequency suggest maybe so

    • The most mild and nice climate that exists, northen parts of northen New Zealand is similar always mild and pleasant and just as green too

  2. Looks like Etna is going for round 2, tremor is rising and a nice ‘pre-show’ is visible.

    • 2 in as many days, seems like another sequence for us to enjoy.

      Its interesting this is in the Voragine and not the SEC, which it is hard to tell but doesnt look like it is even glowing. Maybe these two have a sort of loose alternation. Although, all of the summit craters were active before the 2021 eruptions.

    • Been interesting that unlike the eruptions in 2015-16 these paroxysms are relatively much less intense and are long lived. Its also notable that unless I am mistaken there arent any lava flows. 2015-16 had effusive vents show up elsewhere in the summit area, and the SEC often fot rifted apart by fissures in 2021 only to rebuild just as fast. But so far at least all that has happened now is continuous ashy fountains, I presume the lava is flowing into and filling the Bocca Nuova and will overflow soon.

  3. Magnitude 4.1 quake and aftershocks on the south flank of Kilauea. Hawaii Tracker group on facebook has a lot of reports it felt strong all over the island so it might have been a flank slip quake if a small example of one.

    Would presume the ERZ needs to slip to let magma in but it has technically been slipping since 2018 so maybe there wont be a bigger quake, just sudden decline of all summit activity and the beginning of ERZ inflation again.

    • South flank directly downhill of the ERZ, under the Holei/Pulama Pali, a bit west of the Pu’u O’o lava

    • And now almost as if on que, there have been quakes happening east of Pauahi crater and about under Mauna Ulu, for the first time in about 3 years. SDH is still showing strong uplift, so magma isnt rushing into the middle ERZ, but its still pretty notable that within hours of a probable small scale flank slip the ERZ connector seems to become active beyond the bend of the ERZ.

    • Maybe the inflow of magma forces the south flank to move tectonically and do some earthquakes. But a movent of the south flank may change the geophysical situation for magma flows.
      Concerning deformation the summit has stopped both inflation and deflation since beginning of July. The GPS stations indicate that inflation (and magma) is mostly below the Chain of Craters now, and earthquakes happen between Pauahi and Mauna Ulu. Maybe a short Mauna Ulu eruption is possible. Didn’t it do some minor eruptions before the main 1969-1974 eruption?

      • I dont think an eruption will happen in the Chain of Craters, unless it is very tiny abd gas rich or it cuts across Pauahi crater. Mauna Ulu is actually the highest elevation point on the whole magma system of Kilauea so if an eruption can happen there really all bets are off…

        Its weird though, the tilt at ESC is unchanged, and the tilt at UWEV is showing very slight uplift. But at SDH the tiltmeter is showing strong uplift of the SWRZ connector and deflation from the caldera since July 2. So magma is still going southwest its just not seismic. HVO needs more tiltmeters out that way.

        • The tilt change at SDH is 100 microrad in a month. That corresponds to a 10cm uplift 1 km away, or 1 meter if it is 10 km away. The correct location will be 1-3 km away, I think. There are earthquakes near SDH at the moment, by the way

          • The last Interferogram from HVO had 9 cm of uplift of the SWRZ connector between June 13 and June 29. The tiltmeter shows 45 microradians of change in that same interval, so for 9 cm of uplift the instrument would need to be basically on top of the inflating area, 500 meters off center, which is pretty consistent to the maps and quake locations.

            It also means that the start of the SWRZ connector has actually uplifted about 20 cm in a month. And I remember back when the area started getting really active late last year SDH showed uplift of hundreds of microradians, so maby tens of cm uplift maybe even over a meter in a few months 🙂 although I didnt save a picture.

            I guess, its a rough guess that 5 microradians at SDH is 1 cm of uplift in the SWRZ caldera, which is happening basically every day. 1 cm a day is 3.6 meters a year, crazy. Its even more surprising now that the June 3 eruption was so small and hasnt restarted.

      • ?fileTS=1720301076

        This is one of the stations on the ERZ south flank, on the west side of the Mauna Ulu lava. It is showing the south flank is sliding and it should be filling with magma and erupting but the station is also moving east. The SWRZ is pushing the Hilina Pali area eastwards and it actually is getting in the way of magma flowing down the ERZ.

        It will be interesting when the next interferogram shows the ongoing deformation. The strong swarms on the ERZ connector was because of inflation of the same area but it seems to have stopped and SDH has resumed uplift. My estimate from before was that each 5 microradians SDH moves it is 1 cm of ground movement. The last interferogram was on the 2nd, a week ago, and SDH has gone up 20 microradians, so 4 cm of uplift. Since September last year OUTL and AHUP, the two closest GPS to SDH, have gone up by 60 and 70 cm, after falling a total of about 140 and 110 cm respectively. At the present rate of 4 cm a week more or less both stations will reach their 2018 high in 24 and 10 weeks respectively. So unless something major occurs the SWRZ area will be fully recovered from the 2018 eruption before 2025.
        CRIM station is harder to track without a nearby GPS but it also seems to be lifting at a rapid pace now too. Recent uplift there is a massive 55cm since the start of February, so about 10-12 cm a month, which has been pretty consistent. CRIM has about 100 cm to rise to recover 2018, so at the current rate will do that by mid 2025. UWE has basically already recovered, within the next month.

        To be honest, the amount of uplift is kind of absurd. Its not just one spot but an entire area multiple km across that has lifted about half a meter up in well under a year, around 7 km across.

          • Can someone delete that it saved and posted when I refeshed 🙂 thanks

            Seems there are 12 rings going northwards to where they no longer show. So 18-19 cm of inflation. So maybe SDH microrad to mm is closer to 1/1, or more likely the center of inflation isnt a point source and is a bit variable.

            Either that or I am reading the picture wrong and it actually does show nearly 40 cm of uplift.

          • Ok so HVO themselves are saying over 25 cm of uplift, so I guess SDH is right in the midft of it all and only giving us a part of the picture.

            25+ cm in a month though, nearly 1 cm a day. At this rate the area will be over a meter higher by the end of the year, I somehow doubt that can happen without something breaking somewhere. Im surprised the June 3 dike hasnt reopened at this point, actually its very intriguing that there is such intense deformation but none of the recent eruptions has lasted more than a few weeks and have all failed abruptly. Seems like the drained sills in the summit area have been opened up and the high supply is rapidly filling everything, it might be that once the area is filled to the 2018 elevation things abruptly switch from intrusions to voluminous eruption. So could be a very exiting 2025…

          • Interestingly there is no uplift in the caldera, at least over this time frame. The lack of seismic activity suggests that the area the magma is moving in to is somewhat ductile – a bit like the dead zone. The intrusion is quite shallow as well. No sign of rifting, nor does an eruption seem imminent. Ductile crust can be hard to break. If the inflow continues, it is even possible that the caldera floor will break first and that an eruption would happen there.

          • Yes its very likely that more summit eruptions will happen, the eruption on June 3 was actually higher up in elevation than the floor of Halemaumau, at about 990-1030 meters. And an eruption from the ERZ connector up at the Chain of Craters would ve even higher still, unless it erupts at the bottom of one of the craters.

            Thing is that any eruptions at this elevation wont relieve pressure, as we have seen this past month. Even a swarm of nearlt 1000 quakes in a day on the upper ERZ wasnt enough to cause a new intrusion, where before late 2023 even 100 a day was potentially going to erupt on short notice. Pressure has rapidly increased and is still increasing.

            If we look at the most comparable historical events, they are as follows.
            1959, very rapid uplift and resulting in an unusually powerful summit eruption, then immediately causing a major lower ERZ eruption, and at that point the 2nd biggest eruption in Hawaii of the 20th century.
            1961, immediate recovery of 1960 eruption sees two tiny and one much larger summit eruption followed by a major middle ERZ intrusion that stayed active for 8 years, and was succeeded by Mauna Ulu.
            1975, 6 years of voluminous eruptions and most of the upper part of Kilauea seeing activity, followed by most of a year of rapid inflation without intrusion, until it all gave way at once in that years major quake. Ultimately, Pu’u O’o was created above the area that moved
            2018, same as above, but the middle ERZ was already full, so it all flooded out far east

            What is going on now really is like all of these combined, but point is inflation like this at Kilauea hasnt just resulted in nothing, there will be a big event within the next year that will probably dictate most of the subsequent activity for years or decades to come. Might be the ERZ slipping, it might be the summit starting to fill, it might be a SWRZ major eruption. But it wont just be nothing

  4. Thank-you for the nice volcano tour to Portuguese Hawaii, Jesper!

    It is a real paradise in the Atlantic Ocean with warm climate, but enough rain for prosperous vegetation. I’d classify the Azores together with Canaries as a “medium strong hotspot”, that’s weaker than Galapagos and Reunion, but more active than weak hotspots (with eruptions every ~10,000 years) in the world.

    • Its a rather large plume but its not that super intense , its not as large or hot as Iceland nor is it the insane blowtorch that is Hawaii but it haves an effect on a surface morphology over an 1000 km wide area on the local seafloor apparence.

      • I doubt that it is a plume. The name ‘hot spot’ seems more appropriate. There is evidence for enhanced temperatures below the Azores but little evidence for a mantle plume and more evidence against it (such as the low degree of melt). It has been argued that there has been a plume in the past but that it died – that of course is hard to rule out. (One paper takes the middle ground and argues for a very small plume that formed only a part of the Azores plateau.) The magma seems to be quite wet, and high water content has been suggested as the cause of the melt here.

      • The Hotspot list includes many hotspots that are much weaker than the Azores: https://en.wikipedia.org/wiki/Hotspot_(geology)
        One weak Hotspot is f.e. St. Helena, where Napoleon spent his last years 1815-1821 as most famous British prisoner. The last volcanic event was 7 million years ago, but could still be possible.

        But to come back to the Azores: A nice VEI 2 or 3 eruption there can be more exciting than a grey Plinian VEI 4 somewhere else. The small to moderate eruptions can do a broad variety of eruption types (and their mixtures) as we saw f.e. in La Palma or also in the Vestmannaeyjar twin eruption 1963-1973. They often occur on locations with relative rare volcanism, where it’s like a jackpot win to see an eruption, even if it’s small.

      • Yes Its the dying remains of a mantle plume.. the platform coud be seen as the inprint of the past plume, maybe islands will vanish completely in the future as melting slows down, the whole plateau platform is made from mild alkali basalt, some papers indeed as you say suggests its a “wetspot” where volatile rocks are melting. Another paper argues for two small shallow plume channels near Pico and Faial islands if I remebers correctly. Mantle temperatures are above normal, I remeber reading a few papers suggesting a mantle temperature of around 1450 – 1510 c near Picos shallow astenosphere which is hot enough for more melting than normal, but then Hawaii is likley 1700 c or more so Azores is a midly warm hotspot then

        • The platform sounds like a deeper, and flooded version of Iceland’s platform. Unlike Iceland the Azores Hotspot also has a part of the Europe-Africa subduction plate boundary that meets the MAR in the Azores Archipelago. It could be a mixture of Mediterannean and MAR (Iceland like) volcanism. The Alkali magma remind more to Italy’s volcanoes than Iceland. Flores Island has (according to Wikipedia) an Alkali Basalt, that could be close to Vestmannaeyjar’s Basalt.

        • Yes the magmatic source in Azores was not powerful enough to make it into a subtropical version of Iceland so became a small island group instead of a LIP above the water. Azores is a LIP in defiention but its a rather weak one compared to others that exists like Iceland. Azorian magmas are fairly close to Etnean and Vestmannaeyjar magmas in chemistry roughly the base melt being a mild alkaline basalt, the evolved stuff are trachytes

          • How can we compare the viscosity of trachyte with rhyolite, dacite and phonolite? Which type of magma is most able to form lava flows? I remember that ryholite in some cases built impressive thick lava flows.

          • Viscosity of felsic lava seems to be very variable, some rhyolites and co are actually not that viscous at the vents and flow easily while some form steep domes even being crystal free. Most of the rhyolites in Iceland and the east African rift are pretty fluid and usually not very explosive, probably because of intense heating. Yellowstone and the Andes calderas have much thicker flows of enormous scale, probably because of the thick crust. Yellowstone is very hot while the Andes is probably just the cumulative result of 20 million years of melting and collision, rather than extreme heat.

            New Zealand is probably a bit of all 3. Heat, rifting and a bit of subduction.

        • Phonolite is the most Sio2 undersaturated of these and the least polymerized so is the most fluid among highly evolved magmas if temperatures are high enough, Erebus a crystal rich anortoclase phonolite at 1050 c is quite mobile, mobile enough to have formed etnean looking pahoehoe lava flows when Erebus have had lava lake overflows in the past. Temperatures really helps to lower viscosity in any magma composition

  5. The 1983 Pu’u O’o eruption happened 9 years after the 1974 intrusion/eruption stressed the south caldera and SWRZ.
    Also it was 8 years after the 1975 7.2 Mag earthquake along the south flank. Is yesterday’s earthquake series a foreshock to the middle ERZ unzipping in 2033?

    • Between Mauna Ulu and Pu’u O’o the ERZ never really stopped. 1977, 1979 and 1980 ERZ eruptions happened. Maybe we should consider both big eruptions as the main parts of a long Middle ERZ “Fires” from 1961 to 2018. This 60 years match accidentally well with the 60 years of Ailā‘au eruption.

      September 1961 the eruption was east of Napau Crater, where 1983 the Pu’u O’o eruption began and 1997 was a side eruption.

      • Interesting then to think about the volume, the amount of lava erupted in the Aila’au flows is 3-4 km3 while 1961-2018 without the 2018 eruption is about 5 km3. So more productive niw.

        I think though that the Aila’au eruption wasnt exactly like Pu’u O’o. The longest lava from Pu’u O’o ever flowed was 24 km, while the Aila’au flows went about 40 km. So either the eruption did last half a century and was very episodic in when it flowed so far or the eruption was actually much shorter and erupted faster than Pu’u O’o did. Its probably a bit of both but the particular flow that created Kazamura cave probably had a high flow rate to mame such a big tube and the erosion it shows.

        • I find it hard to believe Aila’au was only 3-4km^3. Not only did it go further than Pu-u O’o, but it covered a larger area than recent stuff. Also Hawaiian Volcano Observatory suggests its volume was 5.2km^3 after accounting for bubbles, which I assume is their way of putting DRE in laymen’s terms. So a bulk volume very similar to the last 60 years…

          https://www.usgs.gov/news/volcano-watch-longest-kilauea-eruption-memory

          • The path of lava flows from Aila’au shield (summit) went between Kilauea’s ERZ and Mauna Loa’s ERZ through the since 1800 lava free territory. I imagine long lava tubes with lava that enter into the ocean south of Hilo. Maybe there is a lot of submarine Pillow Lava lost in the ocean. Erosion has likely also reduced remains on the coast from this eruption.
            Added to this we don’t know how much was erupted on the summit before the later collapse. If we only imagine the whole present Kilauea caldera filled up compeletely and covered with a broad shield volcano, that would be many cubic kilometers.

          • Aila’au did not put any meaningful volume into the sea, unlike Pu’u’o’o which built many lava deltas, advanced the shoreline, and even collapsed into the sea with small tsunamis. Most of the Aila’au flows stalled just before reaching the coast, and the one lava delta doesn’t have much underwater volume. This is discussed in the USGS article Kilauea summit overflows: Their ages and distribution in the Puna District, Hawai’i.

            It also depends a lot on the thickness. We know Pu’u’o’o is very thick in places and would have flowed much further had it not run smack into the ocean. I did an estimate based on the topography and got 3.6 km3 for Aila’au. I was trying to be realistic, that number could be an overestimation as much as it could be an underestimation. There is a lot of uncertainty because flow thickness is difficult to know in a complex flow field like this, particularly close to the summit where it continuously covers a large swath, it depends on how many times the flow resurfaced itself, but I think there is no problem in thin flows at low rates traveling over 100 km in length, more than Aila’au, if the ground is gently sloping like in Pampas Onduladas or the Al Haruj flows. The only way would be to drill a few places and see how thick it is close to the summit.

          • Even if it was 5.2 km3 that is still quite smaller than the past 60 years volume, which is about 7 km3. The lava rock isnt completely solid but the difference between DRE and bulk is not huge, maybe 20%. It us probably bigger for a’a flows than pahoehoe too. Compare this to tephra where the bulk is often multiples of the DRE, part of why I dont find most of the historical Icelandic volcanism to be all that impressive in that regard.

            Aila’au eruption was also at about the same time as a number of Mauna Loa eruptions too, so was not dominant if the plume like Pu’u O’o was. Probably around the same time Kilauea collapsed there was an eruption on the ERZ of Mauna Loa close to the 1984 vents, flowing over modern Kulani prison complex. And there was also the Kipahoehoe eruption on the SWRZ which might have been a similar size to Aila’au. So it is possible the 1400s saw more lava erupt in total than the last 60 years but not individually from one volcano. Although, Kilauea might come close depending on the volume of the Pu’u Kaliu eruption abd when that took place exactly. And on the contrary, 60 years is not a century either, and the next few years is looking to be a real fireworks show.

          • I’m a bit surprised that Aila’au eruption was smaller than the MERZ series 1961-2018. Is a reason for this that the summit is higher than the MERZ vents? If we remember Pu’u O’o, the eruption didn’t stay all the time in the Pu’u O’o shield, but migrated occasionally downwards a bit to Kupaianaha twice, 1986-1992 and 2007. Maybe the relatively low altitude of MERZ vents (mainly Pu’u O’o’s “familiy”) explains the release of a significant higher volume than Aila’au.

          • Pu’u’o’o and Aila’au are eruptions in equilibrium with the magma supply. They are as big as the supply feeding them. Supply is currently very high. In the 16th, 17th, and 18th centuries, very little magma was supplied to Hawaiian volcanoes. Pu’u’o’o might well be more voluminous than the lava production of those three centuries together, as long as there is not a large volume hidden in the Puna Ridge.

            Instead, the late 12th, 13th, 14th, 15th centuries may have been more active since there was a lot of major activity. Kane Nui o Hamo in the 12th century or somewhat later (a predecessor of Pu’u’o’o and maybe similarly big), the major long-lived eruptions of Keapohina (~1200) and Kalahiki-Kolo-Kipahoehoe (probably 15th century and maybe as big as Aila’au) of Mauna Loa, and the filling of the Powers caldera and overflowing during the Kalue, Observatory, and Aila’au flows at Kilauea that took place in the 13th-15th centuries.

        • Aila’au eruption was during a period, when the rift zones were closed for magma inflow. All eruptive activity concentrated on the summit and built a relatively high lava shield above the present caldera. The Aila’au lava flows went along the ERZ on the north side towards the east coast near Hilo. During Summit Shield eruptions lava can reach to areas that usually are thought safe from lava threat.

    • Probably all a lot sooner than that, supply is very high now. The 2018 quake also happened, the south flank has not stopped moving si ce then. So 6 of the 8 years. Really I think it is only the SWRZ pushing at an angle that pinches off the ERZ near Mauna Ulu stopping middle ERZ eruptions now. But with the recent quakes just yesterday that grip might be loosening.

      There was also a SWRZ intrusion in 1981, too.

  6. https://www.youtube.com/watch?v=SlynTN3hSPA

    9:52 showing the flood sheet pahoehoe from Nyiragongos 2021 eruption near a vent… the lava was clearly incredibely fluid covering branches in thin sheets, but I think similar surfaces have been seen at Kilauea too near fast moving vent lava flows in ohia forests

  7. Jesper, can you comment on the recent St George Island tremor crisis? It was thought that a volcanic eruption might occur, so that some people evacuated the island, but it all disappeared into the mists on the internet, when nothing happened.

    • Failed eruption but a very sucessful intrusion, 25 – 30 million cubic meters where intruded I think so not very large compared to other events elsewhere. These intrusions happens a few times every centruy in São Jorge and most dont end up with an eruption last time on land there was 1800 s and possible small submarine events in 1960 s

  8. I really enjoyed ready about ”Shrek slime swamp green” salad bowl! Great article, Jesper and look forward to Part 2.
    Thank you!

    • Hahah almost a meme now…. “What are you doing in my swamp!!!!!!!” … I guess Shrek woud like to have a tree house near the caldera lakes there : D

  9. Thanks, Jesper, it will be nice to read about the big silicic systems of Sao Miguel. Azores is a sizable volcanic province but mostly erupts underwater. A submarine volcano west of Faial, as well as Terceira, have been swarming recently.

    • I will be a tour of all volcanic systems there yes São Miguel is a very beautyful place and very underrated perhaps even or more say un – discovered still by most world travellers. Perhaps not as fun as Hawaii or Etna but fun enough .. and I do think weather is better in Azores than it is in Iceland and Hawaii and better than high summer in Sicily.

  10. This is an excellent article and you paint a beautiful picture of the Azores with your detailed recollections of your trip there a few years back. I would love to visit there if only just for the climate, which sounds ideal for an outdoors holiday. The volcanoes are a bonus. I remember too how you loved the food there, especially the cozido das Furnas.

    I’m looking forward to more of this series.

    • : ) I was there quite recently with GF as well. There will be a part two too thats comming soon, it just needs to be improved and edited and fleshed out somewhat perhaps. Yes despite its weak alkaline volcanoes São Miguel is a very nice place for hiking and geotourism in terms of weather its better than Iceland and Hawaii in those terms, its possible to do alot of active stuff without getting bothered by strong heat or windy cool wet conditions. The weather is also ideal for older persons whose bodies dont cope well with extreme heat or cold. Azores is what we in Scandinavia calls ”pensioners weather” the Island is very calm and sourrene and the archictecture is very beautyful .. very mild indeed.. was T – Shirt weather at lunchtime in Ponta Del Gada in February

      Hahaha the cozido is boiled to oblivion .. the tubers, meat, and others gets turned into an tasteless muck paste but perhaps my taste was poor back then. But I guess your beloved chopper woud instantly consume a plate like mad.. later your canine companion pukes it up in the back car seat.. and the other beagle slurps up the puke 🤣🙈. For myself Cozido in terms of taste was a very weakly watery tasting… sligthly salted.. somewhat meaty carroty like experience. But other foods on the island was absoultely excellent for soure.

      Not all foods are suitable for boling The european strain of potatoes should never be boiled.. as their genetics flaws means they turns to pure sugar when cooked ( cooked = high glycemic index) . I haves them as small raw intensely salted pieces ( raw= low glycemic index) in my sallads and other stuff.

      I guess haves to re – try cozido to see how brain is processing the taste now

    • The submarine enviroment was/is rather strange in Azores its clear and blue like the tropics althrough not quite so much as Hawaii but its still clear and low in nutrients but its too cold for coral reefs to grow. Its also too warm for northen kelp forests to grow there either. That meant the submarine enviroment was rather barren.. no corals, no kelp.. just little fuzzy seaweed that clang to rocks so felt rather empty compared to the Norway kelp forests or the Hawaiian coral reefs. Canary Islands and Mediterranean have similar odd subtropical water caracthers

  11. While the Geology of the Azores is a bit different to Hawaii, it has a similar geographical meaning for the home country. Hawaii is an exotic volcanic island archipelago for the mainly continental USA. In this meaning the Azores for Portugal, Canaries for Spain, Reunion for France and Galapagos for Equador are exotical exceptions for the home country.

    Outside of the Hotspot volcanoes even the Netherlands and UK have their exotic volcanic locations. The Dutch have the Lesser Antilles Volcanic Arc (West Indies), f.e. Saba https://volcano.si.edu/volcano.cfm?vn=360010
    The UK also participate in the Lesser Antilles Volcanic Arc, f.e. with the 2013 last active Soufriere Hills.

  12. Very nice !!

    Don’t the Azores’ submerged vents have a long history of ‘boat thump’ burps ? Not so bad for modern steel hulls, un-nerving for yachties, but must have been *seriously* scary for wooden sailing ships. IIRC, the infamous ‘Marie Celeste’ may have been abandoned at the same time another ship in that area logged, belatedly reported hull-jarring thumps comparable to whale-strikes…

    • Submarine eruptions are common in Azores … alot more common than land eruptions on the Islands, once every 15 to 30 years there is a submarine eruption in the archipelago possibely much more often. If the ocean was drained 100 s of volcanoes woud be revealed in various sizes, many of these are in long chains and ridges or in caotic hilly masses without clear boundaries.,

  13. Unusual locations for earthquakes north of Iceland.

    Thought the main faults were to the west of the line of quakes.

  14. “Stöðugt landris undir Svartsengi síðustu daga” = Continuing inflation/uplift under Svartsengi the last days. Model calculations based on deformation data indicate that magma inflow continues to be higher than before the last eruption.
    https://www.vedur.is/um-vi/frettir/jardhraeringar-grindavik

    Both the breaks and the violence of eruptions on first day have been increasing and continue to be increasing. This tendency will likely lead to larger eruptions in future. Previously I thought that once there must be a plateau or peak of activity, but it shows that the activity is still increasing. The magmatic system of Svartsengi is building up to be able to make big voluminous eruptions.

  15. Seems uplift has leaned into the SW rift, although it is over a more expandive time frame.

    Image removed because of large size. Smaller version below – admin

      • worthwhile checking the size of an image before posting it. They often come in different sizes, and smaller ones are preferred.

    • There are over 26 cm of LOS inflation there, spanning a massive area.

  16. There have been conversations and articles about Mauna Loa’s lower SWRZ. But I do wonder about the lower NERZ. It is much more forested and probably hides things from plain view. But I recently noticed some large shield like vents there.
    So I used a plugin on google earth to see whats under the jungle and saw this:
    Those are some large shield vents from the past 5ka (https://pubs.usgs.gov/sim/3143/sim3143_pamphlet.pdf). Some are not even marked on my map. I wonder why there hasn’t been more rifting there.

    • Eruptions are very rare beyond the 1984 vents. The last major event may have been the Panaewa flow, a likely caldera-forming eruption around 1500 years ago that formed a vast delta in the Hilo Airport area..

    • Wow, I wonder when the last time a Mauna Loa flow interacted with an active Kilauea vent? I bet it’s happened in the past.

      • I remember reading somewhere that it is likely Mauna Loa flows went into the old Powers caldera of Kilauea, some point before 1000 years ago. But that doesnt necessarily mean Kilauea was active at the same time. And generally Kilauea is elevated enough that its vents are not in locations where Mauna Loa can flow over.

        I guess, if Mauna Loa had an eruption like in 2022 but it flowed south towards Kilaueas SWRZ, while Kilauea was erupting there too, then it might be possible, but it is still very unlikely.

        The far distal ERZ of Mauna Loa fasxinates me too, such a rarely active area but all the vents there are huge and the lavas are highly picritic which suggests they are caldera collapse flood lava eruptions. With such a huge elevation difference the eruptions here are probably comparable to the biggest Icelandic eruptions in intensity, though not as voluminous. But still.

        I have also had a theory if there is a possibility some of them are actually very eccentric Kilauea vents, the kind of thing that might happen so rarely that normally evidence is buried by typical activity. There is no evidence to support this exactly but its interesting. Post shield volcanoes often have random vents even if they still have active rift zones. And at Reunion there are rare eruptions northwest of the normal actuve part of Piton de la Fournaise that have much larger eruptions than the typical stuff we see now. Kilauea and Mauna Loa are just so active they resurface themselves faster than the typical recurral time of this type of eruption. It would be quite something though, if Kilauea can accumulate 10 km3 of magma way down and it makes a run for it djrectly to the surface instead of going the normal way, which is what I think Laki and Eldgja were for their respective parents. If Katla and Grimsvotn can do that with 1/10 the magma supply of Kilauea on a good day I dont see why this cant at least be speculated on in Hawaii.

        🙂

    • I’d assume that real shield like vents of Mauna Loa happen at radial vents outside the classical rift zones.

      “Geologists have mapped at least 33 radial vents on the north and west sectors of the volcano”
      Since 1800 there were three recorded radial vent eruptions:
      – 1852 radial vent north of summit (succeded by a classical NERZ eruption)
      – 1859 the famous 300 days eruption from a radial vent north of the summit with a lava flow around Hualalai
      – 1877 Submarine radial vent (Surtseyan eruption) less than a whole day, but shows that radial vents can happen at low, even submarine altitudes

      Has the 1859 eruption created a shield like structure? Imagine something like this at more lower levels

      “Approximately two-thirds (19) of these [33] vents are found on Mauna Loa’s west flank, one-quarter (8) within the north flank, and one-fifth (6) on the southwestern half of the volcano.”
      https://www.usgs.gov/news/volcano-watch-radial-vents-mauna-loas-curve-ball-lava-flow-hazards

  17. Magma accumulation keeps going in Svartsengi the next eruption should be in a few weeks or even less so. It will continues to fill until the crust rips open again due to overpressure

  18. Beautyful Island São Miguel is.. here are the coasts at the oldest part of the Island, that looks almost as old and lumpy as Madiera due to lack of frequent eruptions for 4 million years in this location on Saõ Miguel. The western parts of the Island is younger and alot less eroded than this with clear younger lava deltas around Ponta Del Gada, but here in this area its very old for soure

  19. Where were the continents when the MAR on the Azores began? Were Boston and Gibraltar on the position of the Azores?
    The MAR began to form during the Triassic age. It was 200 million years after the Caledonian orogency. Was there any rifting in the northern Atlantic ocean between Greenland and Skandinavia (Iceland to Jan Mayen) before the MAR commenced?

    • I remember reading that actually the Atlantic basin north of the UK is basically all Cenozoic, the MAR originally went into the Tethys which is mostly gone now (just the Mediterranean east of Sicily left) and it also went up through between Greenland and Labrador at the same time in the Paleocene and Eocene. But I also remember seeing something else a long time back about rifting and volcanism in the modern north Atlantic area way back in the Mesozoic too, so it might be the same as Australia and Antarctica where there was a very long time between the onset of separation and the actual final break. The same thing might be happening in east Africa today too.

      But to summarize the Jan Mayen, Aegirs and Gakkel ridge are all Cenozoic, I dont know when the last rift in the Arctic ocean was before that, probably in the Mesozoic but way earlier. It is very shallow for an oceanic basin too so presumably there has been a very long time since a subduction zone existed up there, maybe not since the creation of Pangea.

      • There is some ancient oceanic crust north of Alaska/Canada, so it would not surprise me if a new plate boundary formed there in the near geological future. There is an ancient continental rift running through the North Sea also.

        • The North Sea is one of the failed rifts during the formation of the North Atlantic. There are quite a few. Eventually a triple point at the south point of Greenland worked, although one of the three arms (going northwest) also failed. 40 million years ago, and possibly a few million years later, there was still a connection between Europe and Canada – if you didn’t mind wading through shallow rifting basins which may have been wet. The rift north of Canada is a lot older: see https://www.volcanocafe.org/white-christmas/

          • Sometimes very old rifts can sleep and awake after many millions of years. The Rhine rifts are an example for this. So it’s possible that there already was a “failed rifting” event between Norway and Greenland between Caledonian orogency and the Triassic age. A failed rift may have created a sedimentary basin between Norway and Greenland that existed until early Mesocoic age.

      • I’d expect that after the Caledonian orogency there was some rifting. Maybe minor, not to produce a whole new ocean, but to distance Greenland (Laurentia) from Norway and Scotland (Baltica, Avalonia) a bit. There was a shallow shelf sea between Greenland and Norway, before the deep Norwegian Sea was created.

        The Norwegian Offshore (Oil Exploration) Office writes about Geology of the Norwegian Sea:
        After the Caledonian Orogency was “B) A series of mainly extensional deformation episodes (Late Devonian to Paleocene)”.
        “Carboniferous, Permian and Triassic: Rifting and formation of N-S to NE-SW trending rotated fault blocks occurred on the Halten Terrace and parts of the Trøndelag Platform in late Permian/early Triassic times.”

        There obviously was some kind of rifting, but it’s uncertain how much and with what dynamics on the surface. Maybe it was similar to failed rifts like the Oslo Graben.

        • More meaning that there wasnt a deep ocean basin between Greenland and Europe before the Paleocene, maybe even not really until the middle Cenozoic. Iceland began forming in the Miocene so it is at least that old though.

          • Not sure why that comment placed here

            Mauna Loa actually has a bit higher MgO on average than Kilauea does I think. Its only a small difference but its consistent.

          • Magnesium was the wrong chemical element. But there was a discussion many months ago about the relationship between Mauna Kea and Kilauea that is more close than the Mauna Loa volcano lifecycle. It’s possible that the postshield stage of Mauna Loa is different to Mauna Kea, and that the shield stage of Kilauea will differ from Mauna Loa’s shield stage and rather resemble Mauna Kea’s shield stage.

          • I think the physical properties of the volcanoes are more important to their evolution than chemistry really. Mauna Kea doesnt have dominant rift zones, and grew up high on the side of Kohala which was already on land. Kilauea might have also started in shallow water but it was completely unsupported so formed very long rift zones, some of the longest of any recent Hawaiian volcano. On Maui Nui the West Maui volcano was similarly formed completely enclosed abd has no rift zones and it is also quite steep with much evolved magma, while Haleakala is gigantic with very long rift zones.

            I think too that the incompatible trace elements are only useful for accuracy of checking the magma source, not for trying to predict magma properties. If theres a 3000% increase in something that is measured in parts per billion it is still only in parts per million after, compared to the major elements that are multiple parts per hundred, or 10000x more abundant. The Kea and Loa chemistry seems to be like that, the bulk composition differs in a small amount for SiO2 and MgO but that can be related to depth of the magma system and its maturity, Mauna Loa is a lot older and taller than Kilauea so also pushes down into the crust, where it is closer to the plume vertically. Kilauea will likely do the same in time, maybe even largely burying the east side of Mauna Loa, as Mauna Loa did to Hualalai which was also a really huge volcano in its prime.

            Im not a geologist, so I am probably getting some stuff wrong, but as I understand it the Loa and Kea trends are not really meant to infer Kilauea is connected to or a part of Mauna Kea, or Loihi to Mauna Loa. Because Kilauea and Mauna Loa do definitively have a connection down there even if the chemistry stats separate. It also has no real bearings on the volcano characteristics, Mauna Loa is big today but there are more of the Kea volcanoes that are similar suze than older Loa volcanoes. And Mauna Kea and Kohala are both Kea volcanoes immediately adjacent but one is a dead rifting volcano with minor post shield and the other has voluminous post shield ongoing and no rifting. And Hualalai is a Loa volcano but has more in common with Mauna Kea apart from also having rift zones, it is very steep and has voluminous evolved magma in the past, enough to build a sizable new shield.

            Hopefully someone who knows a lot more about this can correct me if this is wrong.

          • If we look on the behaviour of the volcanoes, Mauna Loa has a very clear pattern, while Kilauea is more variable. Mauna Loa usually follows this timetable:
            1. A Curtain of Fire fissure eruption from upper SWRZ through Moku‘āweoweo until the NERZ top end. 2. After some hours a shift towards a single location, sometimes downrift, sometimes towards a vent on the summit. 3. The eruption stays for the rest of time on this single location, for days or for weeks.

            Kilauea does sometimes summit eruptions first and rift zone eruptions afterwards (f.e. 2008-2018 or 1954-1955), but that’s far from being a rule. It is more unpredictable. Sometimes Kilauea does very short eruptions like the tiny June 2024 SWRZ eruption that was shorter and smaller than Mauna Loa 1975. Sometimes Kilauea does endless longterm eruptions like Pu’u O’o that dwarf any longterm eruptions of Mauna Loa.

    • Its already changed more in the last 30 years than the past few centuries before that. 1996 to present has been insane. Big eruptions and paroxysms happened before that of course but were usually effusive flows at low vents, where now such eruptions are only still in the summut area and secondary to the main craters. And the only exception in 2001 and 2002 was an eccentric dike that basically acted like a summit eruption anyway. Combined volume of magma erupted in 2001 and 2002 flank eruptions is probably something like almost 0.2 km3, and more than half of that was turned to tephra, it would have been a VEI 4 if a single eruption.

      And since 2000 there has been like 400 paroxysms too 🙂 maybe not exactly that but close.

  20. https://www.bigislandvideonews.com/2024/07/11/kilauea-volcano-update-for-thursday-july-11/?fbclid=IwZXh0bgNhZW0CMTEAAR3FCyBboR1gyEtcWCqmEDYBJXEHd-EmMptwgWBi-JcNTURRXZJoEAagNFg_aem_fuXMMMeVGItYu9CnUwDdhw
    “Over the past 24 hours, there were approximately 52 earthquakes detected beneath Kaluapele (Kīlauea caldera) and 5 earthquakes detected beneath the upper East Rift Zone, mostly at depths of 0–2 km (0.0–1.2 mi) beneath the ground surface. Counts increased beneath Kaluapele”

  21. Hahah I tryed to swim in Azores but was barely do – able in may 🙈 I saw a nice piece of fiammed ignmigbrite in the water so descided to get it anyway as it shimmered in the water a piece from one of Auga De Paus ashflows… eastern northen atlantic is far colder than western parts of the atlantic for soure.

    • How much colder was Azores during the last glacial maximum? its a subtropical oceanic climate so little affected by large changes on the continents due to strong oceanic moderation. Well Im right reading the computer simulated LGM climate conditions gives only a very small change in land temperatures and the sea. Since the polar front woud have been depressed its possible the Azores woud have been even more rainy than they are today even since low pressures woud have been pushed south by polar air

  22. Svartsengi is inflating quite nicely now that it has shut down! Last couple weeks it has been inflating at a similar rate to prior eruptions, faster than before the most recent one.

    Looking at the graph, it will reach the level it erupted last time in about 3 weeks! So maybe sometime in August, if trend toward bigger eruptions continues?

    Here’s the link:
    https://en.vedur.is/about-imo/news/volcanic-unrest-grindavik.

    • Also notable is how the initial dike was easily triple the size of even the most recent eruption. Svartsengi may be just starting to gear up. If so frequency will go down. It would take something like 6 months or so without an eruption to build up to an initial-dike sized eruption with its feed rate.

      • Svartsengi is on the path to align more to the major Icelandic volcanoes than the tiny first Fires episodes. In the end Svartsengi and Reykjanes Peninsula as a whole may become as active as Vatnajökull. It’s possible that once we get dormant periods of five years between eruptions, that then remind to Grimsvötn’s average eruption volume.

    • The amount of land rise can be seen here https://strokkur.raunvis.hi.is/gps/8h

      Scroll down for Svartsengi SENG. It’s interesting that while this station does not show more inflation than all the others, it is however nearly at the previous high point.

      The high points from the previous eruptions have dropped off the graphs, but IIRC the last eruption was “higher” than the preceding ones. I think this one may go even higher.

      • I always check HS02 first, closest to the sill.
        GRIV has been pushed south over time, HS02 slightly north, and THOB east.
        SKSH slightly north and west, whilst ELDC has been westerly.
        So the sill is really just west of Thorbjorn

  23. Video of Etna recently, showing lava has filled and is overflowing Bocca Nuova

    And, now with confirmation, Etna has got a lava lake 🙂 Its not as fluid as some others but it also is clearly still free flowing

    https://youtu.be/xJEcbjdrZUo?si=IbaAHL-auU3n0f0s

    I can see in the future if the conduit gets wider and allows convection it could become te real deal.

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