The secret lives of volcanic islands

/ 16/04/2023

The Late’iki eruption of 1995

Land is precious. The saying goes ‘Buy land – they don’t make it anymore’. We need the land to live on, to grow our crops, to socialise, work, educate, and all other things that makes human life worth living. Even our touch phones won’t work under water. With a growing population, the pressure on the available land increases every year. So do buy – it is an investment. But be careful what you buy. If you live in New Mexico, check whether the land also includes the water rights. If you live in Florida, a 100-year mortgage may find the rising sea overtake you before it is paid off. And buying land close to a youngish looking volcano could be considered a gamble. Especially if that volcano is underneath you.

The expression leaves it unclear who the ‘they’ are. Who made the land? Can we take it into our own hands? The person who invented the expression had probably not been to the Netherlands! But it is also possible that the person had discounted land created below sea level as not worth buying. Expanding a country the Dutch way comes with risks. It is a risk that more and more nations will need to take to keep up with the rising sea. Nowadays, it takes effort to keep what you have.

The ‘they’ mostly refers to nature. The Earth does build new land. Can we enlist it? A cheap way to expand the available land would be to get a willing volcano to kindly steer some lava towards the coast. Trust is important: lava going the wrong way could undo all the good work. But if you can’t trust a volcano, who can you trust?

A less (or more) intrusive way would be to keep the lava (magma) underground but use it to inflate the land, thus pushing back the sea. Iwo Jima has been doing this for centuries. What could possibly go wrong? Of course, you may suddenly find your nice newly inflated land exploding and covering most of the neighbouring countries as a deep layer of volcanic ash – liability insurance is recommended. And what goes up can come down: Naples has had its impressive ups followed by meters of decline, with a major Roman resort now 12 meter deep under water. I expect they did not see that one coming! People are remarkably poor at understanding risks.

Back to valuable land. Strangely, the most valuable land is also the most isolated. All sea-facing land comes with a 12 nautical mile territorial claim on that sea, plus a 200-mile exclusive economic zone. Where such claims overlap, a line is drawn through the middle. Not everyone agrees (China draws it claimed border on the beaches of the neighbouring countries) but this is the UN convention of the law of the sea. (There is an exception for continental shelfs.) Now, an island far away can become valuable property even if the land is barely habitable. An island has coast on all sides, and therefore it has a very large economic zone. There are some restrictions: the island should be above water at all times, it should have a natural origin, and most of all, it should exist. Not all islands meet these requirements.

New islands

Qeqertaq Avannarleq was discovered in 2021 by a team visiting Oodaaq, the (reportedly) most northerly island in the world, located off the northern coast of Greenland. The team landed their helicopter on the island, and send the coordinates back to the world. Very quickly the comments came back that they were in the wrong place. They had ended up on the wrong island, 750 meters north of where they were supposed to be. Their newly and accidentally discovered island consisted of silt and gravel, 50 meters across and up to 4 meters high. It may be the result of storm debris, and could be destroyed by one as well. But for now, this is the most northerly island in the world. It extend Greenland’s territorial waters by 5.6 km2. Not bad for an island that is only 0.0018 km2 in size! The economic zone is now 24 km2 larger.

Whether this will be accepted depends on the longevity of the island. There is an ongoing discussion whether Qeqertaq Avannarleq (‘northern island’) should be called an island. Several similar islands have been discovered in this region in the past, to disappear again later. The off-shore region has a moraine bank under water, and shifting ice can push up the bank to form an island, and similarly make it disappear later. A shifting sand or gravel bank may not deserve the name of ‘island’. But it is fun to find new land.

Phantom islands

Ephemeral islands have appeared in many places. They were found, mapped, and disappeared leaving people to wonder whether they had ever existed.

The north coast of the Yucatan borders the Gulf of Mexico. There are a few reefs and islands about 100 km off the coast: the beautiful Scorpion Reef, the Cayo Arenas, Triangulas and Cayo Arcos, forming an archipelago of low sandy islands. They are rather hard to reach and have no facilities whatsoever – they are for the ‘adventurous visitor’. A bit further from the coast is the very similar island of Bermeja, discovered in 1539 and described as having ‘red-blond soil’ (which explains the name) and as a bit less than 10 by 10 km in size. It is located at 22°33′ N, 91°22 E in the Gulf. At least is used to be.

The 1539 map showing the precise location of Bermeja

But after its discovery, no one ever saw it again. The 1921 Geographic Atlas of the Mexican Republic still included the island, but by that time other cartographers had given up on it. It was reported to have sunk ’60 fathoms’. In the late 20th century, the Gulf of Mexico became an important source of oil. The ownership of that oil was negotiated between the US and Mexico. The region north of the Yucatan was put on hold until 2009, pending searches for the missing island. Had it sunk a bit, as sandy islands sometimes do? Had one of the hurricanes knocked it back to below sea level? This was now important to know, since if the island (or its remnants) could be found Mexico had a claim to a significant larger area in the Gulf. Searches were made both in the late ‘90s and in 2009. Bathymetry indicated only deep sea sediment at this location: there was no evidence for any shallow remnant. The island had never existed and Mexico had to give some of the oil wealth of the Gulf.

What happened? There are two main possibilities. The discovery may have been one of the other islands to the south, and the ship had its own location wrong. Those things happened: this was the 16th century when deep sea location were in part guess work. The original record may also have been intentionally misleading, to put the competitors off the track and make them avoid a supposedly dangerous region. You do not want to run aground in a dark night far from any help. Those things, publishing deliberately misleading maps, happened too. There are other proposals around but those are best dismissed out of hand. No, the CIA did not blow up the island to extend the US rights further into the Gulf. The 2008 investigators concluded that the original descriptions of Bermeja were so precise that it is likely that the island did exist. Just not in this location.

Phantom islands happened more often. Benjamin Morrell, a 19th-century sealing captain, published a memoir called Narrative of Four Voyages. Although some of the content was correct, much of it was fiction. Several phantom islands owe their existence (or rather phantomness) to Morrell. These include Byres Island and Morrell Island, located northwest of Hawai’i. The International Date Line was drawn to go around these islands, until in 1910 their non-existence was discovered and the date line could be re-straightened. False facts are nothing new, and 19th century readers were just as prone to believing made-up stories as the current twitter generation.

The Aurora islands are another example of disappearing islands, but different since they were seen several times. They remain a bit of a mystery. The origin is in 1502 when Amerigo Vespucci joined a Portuguese expedition off the Atlantic coast of Brazil. The following is quoted from wikipedia:

we found ourselves in latitudes so high that the midday fix was 52° above the horizon and we could no longer see the stars of the Little Bear nor the Bg Bear constellations. This was the 3 April 1502. That day a storm blew up so strong that it made us furl all our sails and run with bare masts before strong winds from the south-east, enormous seas and stormy gusts. Such was the tempest that all the fleet was greatly fearful. The nights were very long, and the one of 7 April was of fifteen hours duration since the sun was at the end of Aries, and in this region it was winter, as Your Majesty can calculate. In the middle of this storm of 7 April we sighted a new land, which we sailed alongside of for almost 20 leagues, finding the coast wild, and we did not see any harbour or people. I believe because the cold was so intense that none of us could remedy it or bear it.

There is some confusion here: the 15-hour length of the night at that latitude actually is in early May or August, not April, so the stated month is clearly wrong in spite of the precise detail. The statement that it was winter and the claimed cold also agrees better with a later time of the year. But clearly, any land 100 km long is worth claiming. The land was found again in 1772, and at that time the longitude was noted and it was stated to consist of three separate islands. Their existence was confirmed in 1796 and again in 1856. And they were never seen again. The location is midway between the Falklands and South Georgia where only empty sea exists. In the late 1800’s, maps stopped including the Aurora Islands. How could this have happened? The original discovery reported by Vespucci is a bit vague. Was he perhaps much further east and was this South Georgia? Was it the Falklands? Or perhaps the southern coast of Brazil? Or, dare I say it, was it made up? The vagueness and errors in the report sound more like hear-say, which Vespucci perhaps wrote up and tried to pass off as his own discovery. Once the island was ‘known’, it became self-fulfilling: people seeing something in the distance where the maps said there should be an inhospitable and dangerous coast, would identify it as that land and stay well away. The later reports may even be from icebergs: they can appear like land from a safe distance.

These are a few examples of the many phantom islands, islands which at one time existed on the maps but could not be relocated later on. A brilliant overview can be found at http://andrewpekler.com/phantom-islands/. It is wel worth spending time there exploring a phantom world.

But some islands really do appear and disappear. These are volcanoes at work, often in secret and unobserved, their handiwork like a Banksy appearing overnight.

The deep sea

Before and island can emerge from the deep sea, major building work is required. The ocean is kilometers deep, and any island needs to grow to at least that height before it can make territorial claims. There are two ways this can happen. The first is buckling of the oceanic crust, and it happens at a subduction zone. The descending plate creates a deep trough, easily spotted on maps of the sea floor. But as it descends, it locks to the other plate and pulls it back. That plate buckles and can rise above water. Kodiak Island off the coast of Alaska is an example. Another example is provided by Chichijima Island, part of the Ogasawara (or Bonin) Islands south of Japan.

The other way is volcanic. There are again two ways this can happen. The most familiar one is where a patch of excess heat in the mantle melts part of the upper mantle and grows a volcanic island. This can happen anywhere on Earth but is easiest on a spreading ridge where there is a ready-made transport route from the mantle to the surface, and only little extra heat is needed. Elsewhere more serious heat is needed: Hawai’i is a good example of such a hot spot.

The second volcanic way is again related to subduction. When the subducted plate gets deep enough, the water-saturated crust wets the mantle just above it and thus lowers its melting point. Melt accumulates and begins the arduous journey to the surface. This forms a volcanic ridge a few hundred kilometers from the subduction. The map of Japan above shows this volcanic ridge well separated from the buckled crust. The melt inflates the whole length of the ridge but only the individual volcanoes manage to puncture the sea surface. If the melt occurs below continental crust, you can get an elevated and mountainous ridge, with volcanoes on top (or just beside the elevated ridge– magma can take funny paths). Indonesia is good example.

So now you know why Kodiak Island has no volcanoes!

Tonga: Late’iki

Volcanic islands can seemingly appear out of nowhere. We are oblivious to the building work that prepared for the emergence. A familiar example is Surtsey which suddenly formed in November 1963. (That was on the shallow sea surrounding Iceland, so not an example of a deep-sea island.) The first sign was a sulfur smell, and shortly after a column of black smoke heralded the birth of new land. That was 60 years ago and the island is still there, qualifying as a territorial marker under the law of the sea. Neptune, of course, ignores this law and claims it all as his own anyway. Perhaps Surtsey tried to escape from the rule of Neptune into the freedom of the air.

Surtsey is just one example among many. Reports of eruptions breaching the surface are far from uncommon. Hunga Tonga is such an example. Before its spectacular destruction last year, it had existed only for 6 or 7 years. The island had formed from an eruption in between two smaller islands, which became incorporated in the new island. The four-part full name abbreviated as HTHH still refers to those two fragments.

Hunga Tonga is part of a volcanic arc caused by the Tonga Trench (a name that has a ring to it). The map shows the main Tonga islands located on the buckle ridge, and the separate line of seamounts and volcanic islands. The ridge is paradise. The volcanic arc is the brutal world beyond paradise, outside of the eastern gate. (Actually it is to the west – the analogue does not quite work in this case.) It is a place best studied from a safe distance. Surtseyan eruptions are common here. Hunga Tonga had them in 2009 and again in 2014/15, whilst Home Reef (what’s in a name?) erupted in 2006 and 2022, and Late’iki erupted in 2019. Definitely not a place to call home. It is a place to stay away form, and that s what people did.

The Late’iki eruption of 1995: creating new land

In spite of this, Late’iki is worthy of attention. The intermittent island has erupted ten times since 1851. Islands were formed in 1967, 1979 and 1995. It had to go through this island birth process three times as the islands of 1967 and 1979 lasted only a brief time before Neptune reclaimed the land. 1995 was more successful and the island that was formed in that eruption remained. The eruption started on June 6 and by the end of the month, the island was 300 meter long and 50 meters tall. This was the real thing. The previous eruptions had build tephra cones, presumably because the eruption itself had remained under water. In 1995 the eruption became exposed and now the new land was made out of lava – rather sterner stuff than tephra. On 14 October 2019 a new eruption was observed by a passing ship, and yet another island formed: New Late’iki.

As we know from Hunga Tonga, the volcanic arc is not well monitored. Even in today’s world, the Tonga volcanic arc remains a good location for a secret eruption. Satellites provide the best images but they may be available only one for every few days, and of course clouds may get in the way. The images above show satellite images of the events of 2019. In the first image, the Late’iki island of 1995 is clearly visible, surrounded by the cyan ring indicating shallow water. The eruption disaster struck on October 15. The image captured a big explosion near the island. By the end of the month, a new island had appeared, in an arc around where Late’iki had been – but no longer was. The 1995 creation had been destroyed in this eruption. The new island was not nearly as sturdy as the old one. Over the next months it rapidly reduced in size and it was last seen on Dec 9. The next image, Dec 14, shows shallow ocean but no land. (Images from Plank et al. 2020).

The eruption had been much more significant than it seemed at the time. The quick dispersal of the new island showed it consisted of debris. The arc suggests it was debris from Late’iki. The eruption had blown up the entire island! It hadn’t been a large island, but still. Any eruption wiping an entire territory of the face of the sea is worth noting. In hindsight, this seems like a dress rehearsal for the Hunga Tonga, the loudest eruption since Krakatoa!

Volcanic islands live and die by the power of the earth and sea. They are a battle ground. It is always worth checking in the morning what may have appeared overnight. To quote Carl: I love the smell of a fresh volcanic island in the morning.

Didicas volcano

The ocean north of the Philippines is dotted with small islands. In 1857, an eruption added one to the collection. The activity lasted four years and by the end the new island was reported as 200 meters tall. It didn’t last. Within decades the island was gone – surprising, in view of the height. The island reformed in 1952 and grew even taller than before: 240 meters. Since 1979 it has been quiet. But the Philippines newest island still exists.

Krakatoa

The most famous of all is Krakatoa. Before the cataclysmic eruption, it consisted of four separate islands: the main, large one, two flanking islands and one standing rock called Polish Hat. When the island exploded, the flanking islands survived, as did the south end of the main island. Polish Hat was demolished, in spite of not being near the actual explosion. It may have been destroyed by the massive tsunami, which (scaling from Hunga Tonga) may have been over 100 meter tall in this location. The net number of islands thus did not change.

Polish hat remains a bit of an unknown. We have no detailed description other than that it consisted of glassy, greenish-black rock, identified as a dark andesitic obsidian. Verbeek spend a few hours (at most) on Polish hat in July 1880. No images or even drawings of it remain. It really has become the phantom of Krakatau.

Once Anak Krakatau appeared, there was one more island than there used to be. Its subsequent collapse in 2018 left the new island itself in place. It is now regrowing its cone (and its danger). Over the next centuries, Anak Krakatau may rejoin with the surviving side of the original island. Volcanic islands are dynamic. Here today, gone tomorrow, back next week.

Limits to the growth

These island forming events are quite common. The destruction events are almost as common: most new islands will exist intermittently and go through phases where they are present and where they have become phantoms. But that constant turn-over is surprising. The islands form in the deep ocean (the exception is Krakatoa which is on the continental shelf). Before they can breach the surface, they already have grown kilometers tall. These are not new volcanoes: they are fully grown, mature beings. They are not mayday flies. So why, after growing up several kilometers, do they suddenly balk at the next 100 meters and can’t quite make the jump to the next level? And why do all these volcanoes, in oceans of different depth, get stuck at the same level?

Aerial volcanoes behave differently from submarine ones. Submarine volcanoes are steeper than aerial ones. This has two explanations. The slope is determined by how far lava can flow: the further it gets, the shallower the slope. Under water, lava cools much faster, or at least the surface solidifies. Now it becomes sluggish. The same lava will flow further in air than it does under water. The fact that the water carries a third of the weight of the volcano (through water displacement) helps to stabilize the steeper slope. Therefore, the under-water part of the seamount can be steeper than the part that sticks out above the water. The underlying slope can be hidden by the loose sediment on top which has a much shallower slope. Volcanic islands may have thick aprons formed by debris coming down the slopes. But seamounts often grow steeper towards the surface.

This makes it harder for the volcano to grow once it reaches the surface. In order to grow taller, it needs to grow wider. On a kilometers-tall mount, that requires a lot of lava. The foundations were made too small.

The second explanation has to do with the ocean surface. It creates a hostile environment, with wind and waves and rain and snow. As soon as a volcano reaches the surfaces, it becomes ruled by the waves. Wave erosion attacks the edge and eats away on the new island. It takes tough lava to survive this, and in the end the waves will win. Below the surface, where everything is quiet, there is much less erosion.

Wave erosion attacks from 10-30 meters below the surface to 10 meters above it. This is the danger zone which the island must overcome. It does so by growing wide: the larger the circumference, the better protected the island is. But this runs into the previous problem, that the mounts needs to grow larger foundations.

The effect is that many seamounts end up with a flat top, some 10-30 meter below sea level. This is the effect of wave erosion.

An example is Iwo Jima. The island is in effect the tip of a large cone, and forms a low flattish area, surrounded by a ring which in places sticks out above the water. The flat area was shaped by wave erosion, even though it is now well above sea level. This is not due to eruptions: Iwo Jima only has very minor eruptions which do not add to the height. The area has grown above water not by erupting lava, but by rapid inflation. The magma below the surface is pushing it up.

Some seamounts have flat tops but 100 meters below the surface. They show wave action much deeper than expected. These tops date from the ice age when the sea level was 100 meter lower than today. They can be anywhere from 10,000 to 500,000 years old – that is the age when the top was flattened, and is probably near the time of their most recent eruption. Much lower tops are also possible. Those are Iwo Jima in reverse: once the magmatic heat is turned off, the volcano cake deflates and sinks. Flat-topped seamounts below sea level are called guyots.

Source: https://www.pmfias.com/ocean-relief-major-minor-ocean-relief-features-continental-shelf-continental-slope-continental-rise-abyssal-plain-trenches-submarine-ridges-abyssal-hills-submarine-canyons-atoll-bank-shoal-reef/

So to overcome all these difficulties, a volcano wanting to become a lasting island has to grow fast through the ocean surface. If it is too slow, it will get stuck in a cycle where it builds a small island which the waves take down again before the next eruption. This happens in many places: it is the reason we have so many phantom volcanic islands putting in a brief explosive appearance before being removed again from the aerial world. Neptune’s border control can be harsh.

Collapse

There is one further problem. There is a maximum slope any mountain can have before it fails. The slope depends on how hard the rock is. Volcanic mounts tend to have a lot of low strength material on top of the steeper lava cone. This is not strong and cannot carry much weight. A steeper slope has to be stronger. Growing a mountain from the top makes it steeper, as shown by the concave shapes. Lava flowing into the sea can cause very steep slopes because the lava solidifies quickly under water. Flank eruptions give a shallower, more stable shape but does not make islands from a seamount. If the top-heavy mountain already grew on a slope, as Anak Krakatau did, it gets even worse. The side of the mountain can collapse with potentially devastating consequences. In 2018, Anak Krakatau’s entire aerial cone slid into the sea; the displaces sea water caused a large tsunami. I have a suspicion that the main explosion of its daddy, Krakatoa, similarly coincided with a flank collapse, in the same direction as its descendent.

Island volcanoes can be intrinsically unstable. All the work the volcano does in growing above water may eventually be in vain. Neptune reclaims it’s own.

The end

This is the ephemeral landscape of ocean islands. They come and go at a whim, always at risk of explosion and collapse. It is a dangerous world out there. Explorers may indeed suddenly find an island no one had ever seen before, or fail to find one that existed a week ago. But explorers explore to become finders. They need to discover to justify the effort. And so they found and recorded finds which in hindsight are highly dubious. Sandy island off the northwest coast of Australia, found by Cook, never existed. Neither did the Aurora islands. But they could have existed. And they may still do.

Albert, April 2023

And some volcanoes are true phantoms. Read the story of the Florida volcano

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73 thoughts on “The secret lives of volcanic islands”

  1. Beautiful. It reminds me of fun days watching Bogoslof building up and blowing itself away again.

    • Yes, Bogoslof was an experience. Here is a Sentinel image from last week. The island still exists but has become smaller.

  2. Did Ontong Java Plateau form a Mega sized ocean Island? Papers say it rised above the ocean: 100 million km3 and most of that in just a million years is kind of rad

    The bigger the volcanoes the better

    • Wrangellia is an example: it includes crust from an oceanic flood basalt. Kerguelen may also be such a case. A modern case is Iceland. Basalt is heavy, and if not supported by continental crust it will eventually sink below the waves but while erupting it may well be an island

    • Iceland is a rather slow LIP, its not at all like the “Superplume” LIPs like OJPL was

      • But it did manage to make a large island. This answers you question, I think. Oceanic LIPs should be able to make islands 500 km across or more. The size is set by the plume head, not by how far the lava can travel

      • OJP was a much more powerful plume than Iceland is today thats for soure I think the Island grew much bigger than Iceland

        Lava retains its heat well and can flow miles miles underwater If eruption rates allows it, water only cool the surface forming an insulating crust as seen by the lava stalagmites in submarine collapsed seafloor lava crusts

        • The lava will certainly have gotten much further than 500 km, if only through dikes. But for an ocean LIP to grow above water, you need more than lava. Lava has the same density as oceanic crust, so will sit equally deep – you will end up with 2-4km below sea level. It is the heat from the plume head that raises the LIP above water, and that heat does not extend as far. A large plume head may be 1000 km across. That is still a very decent island! And would increase sea levels considerably elsewhere

        • Does Iceland contain a little bit of continental crust in it’s basement? There’s also the question…at what point does the crust produced there become continental…

          • Continental crust is much lower density than oceanic crust. That is why the continents sit several kilometers higher than the ocean floor. It gets that way by separating out the heavy stuff (iron, magnesium) and leave the lighter weight things (silicates). That happens in melt. Iceland does not do this separation: it melts too much. So it won’t make a continent. Oceanic island so sometimes get plastered on to continents and become part of them, but they need the continent as a flotation device

      • A really bad plume head coud be thousands of km wide, OJP had huge submarine lava floods emplaced by 10 000 s of thousands of cubic meters a second perhaps millions or even billions ( many cubic kilometers or Leilani volumes flowing out per second ? ) during souch speeds the water dont cool the lava much at all and you gets ”submarine sheet flows” rather than pillow lava.

        All Oceanic extinction scale LIP s are generaly built by massive Fissure feed submarine sheet flows. But it only seems that land based LIP s cause extinctions perhaps because the ocean absorberas the gases

        • Superplumes can have effects 5000 km away. It requires a rising plume perhaps 1000 km across. The main heat is in that central area but you may get some uplift much further away. The lava flows are ‘not important’ for this because the lava os so dense: it just makes the crust sit deeper. It is the uplift even before the eruption begins that creates the land

    • Some papers say that just a small part of it was subaerial. I think it is not known precisely. The sea levels were a lot higher, not to forget.
      On source says there might have been a spreading ridge there once. On the other hand there might have been a Triple Junction between the growing Pacific Plate and the Izinagi and Phoenix Plates.
      Some sources say that research above the OJP plus bathymetry there is underwhelming.

      This article is about Malaita which is thought to be part of the obducted southwestern margin of the OJP which would mean that it IS partly subaerial:

      “INTRODUCTION
      The island of Malaita, Solomon Islands, has been recog-
      nized as a part of the obducted southwestern margin of
      the Ontong Java Plateau (OJP), which is the world’s
      largest oceanic plateau or large igneous province (LIP),
      occupying an area of at least 1600 km 800 km (e.g.
      Coleman & Kroenke, 1981; Tejada et al., 1996; Petterson
      et al., 1997) (Fig. 1a).”
      https://www.researchgate.net/publication/277372442_Layered_Lithospheric_Mantle_Beneath_the_Ontong_Java_Plateau_Implications_from_Xenoliths_in_Alnoite_Malaita_Solomon_Islands

      Enjoy!

    • I don’t think the Ontong Java Plateau formed an emerged island mass. When a volcanic island emerges above water, it leaves a topography shelf. The submarine flanks being very steep, made of unstable lava deltas. As the island gets eroded, the part above the water is removed and the underwater part remains, making a shallow guyot. You can see very well in Iceland or the Hawaii-Emperor Chain which portions were emerged. In the Ontong Java Plateau, there are no topographic signs of the plateau ever being emerged.

      I’ve been playing with a Global Gravity Anomaly kmz from the University of California San Diego and its beautiful how big oceanic volcanoes come into sharp view as positive anomalies. One of the biggest disappointments, though, has been seeing how the Ontong Java Plateau is so subtle that is practically invisible in the gravity anomaly map. It’s probably a very thin sheet of lava flows, I think, and probably over-hyped.

      That also shows how exceptional Iceland is. I think Iceland might be the largest emerged oceanic lava plateau that we know of. Iceland is an elliptical plateau with 280,000 km2, most of it was above sea level during the Ice Ages, and the parts below sea level were probably covered in thick glaciers that were eroding into it, making glacier deltas that are visible on all sides of the Iceland plateau. Northen Kerguelen, that was active in 30-24 Ma, formed an elliptical plateau of 80,000 km2 that is still very shallow and was emerged during the Ice Ages. That is less than a third the size of Iceland! Other parts of Kerguelen formed subaerial islands earlier, but I think smaller than Iceland too. Hawaii is 10,000 km2 in comparison, although a few times thicker than Iceland and formed in 1/20th of a time.

  3. A pretty narrative introduction to the variety of volcanic islands! Volcanic arcs on subduction zones may once have been the first seeds of continents. They create light rock (by evolved magma) which swims better on the mantle than basaltic oceanic rock.

  4. Writing my IO articles .. pretty badass stuff is one and the other is just a broad overview of Ionian Volcanism

    Walking Io s surface is my dream
    At least a rover should do that as the radiation shielding exist

  5. Question I have that was cued by some of the comments on the last blog as well as on this article.

    With what we know about tsunami wave dispersion from point sources, is the tsunami risk from a caldera forming eruption at Ioto / Iwo Jima far than was originally thought when the VC wrote the original article? https://www.volcanocafe.org/the-new-decade-volcano-program-no-1-ioto-japan/

    Also, on a separate, but related topic, do we know of any significant paleotsunami deposits in east China? I would guess there hasn’t been a ton of research done on those, but if a large caldera forming eruption would definitively cause a tsunami as far as China, then there should be some evidence for a similar or even larger tsunami deposit from the Kikai eruption south of Japan.

    • One of my favorite pieces. This late Henrik must have been a bag full of sarcastic humour which is always so close to political realities. “Jaws” shows precisely what is going on in those heads.

    • There are no studies of such events. I expect they will be done now that Hunga Tonga has shown the danger. Kuwae is another example. In principle, a volcanic ‘point source’ is not as effective at larger distances, but Hunga Tonga was only a high VEI-5 or low VEI-6. A badly located larger eruption could generate a larger tsunami. There are few studies of tsunamis in the South China Sea but they have occured. A model of an ancient landslide in the South China Sea predicted a 17-meter tsunami. Also see this article

      https://edition.cnn.com/2019/01/03/asia/china-guangdong-tsunami-study-intl/index.html

      • I wonder what is more effective for volcanic long distance tsunamis, column collapse PDCs or submarine explosions, Krakatoa vs Tonga? It’s impractical to compare the 2 due to differences in location and time but I’d put my money on Ignimbrite emplacement. The energy of tens of cubic km of magma from column collapse crashing into the sea would easily exceed 800 megatons.

      • Answer to Merlin:
        Tambora is in the middle of a peninsula belonging to an island. The distance to the coast on three sides is about 35 km.
        This might be comparable to El Teide Tenerife which is surrounded by coastlines on all sides though. Traces have been found of two considerable tsunamis (a rare event says the paper) 170 ka:

        “Here we document tsunami deposits at high elevation (up to 132 m) on the north-western slopes of Tenerife, Canary Islands, as a new evidence of megatsunami generated by volcano flank failure. Analyses of the tsunami deposits demonstrate that two main tsunamis impacted the coasts of Tenerife 170 kyr ago. The first tsunami was generated during the submarine stage of a retrogressive failure of the northern flank of the island, whereas the second one followed the debris avalanche of the subaerial edifice and incorporated pumices from an on-going ignimbrite-forming eruption. Coupling between a massive retrogressive flank failure and a large explosive eruption represents a new type of volcano-tectonic event on oceanic shield volcanoes and a new hazard scenario.”
        https://www.nature.com/articles/ncomms15246

        “potentially represent a high-magnitude but low-frequency hazard”
        says the paper which means to stay balanced with this risk. There is now a bit of hysteria (personal feeling) after HTHH.
        The bay of Naples is certainly a “high-magnitude” risk zone though.

        The tsunami risk of a flank collapse on Isla de la Palma is thought to have been exaggerated. A tsunami caused by submarine earthquakes is a different story though as we all know from Sumatra 2004 and Japan 2011. This might also concern Portugal one day, and the same goes for the region of Messina.

  7. The Potrerillos Caldera to the south of CCN has seen a significant reduction in inflation. The volcano seems to be experiencing minor uplift (1-2 cm/year) and some deflation. Since the swarm last year, a new uplift zone has developed a few km to the S of the Chiles cone, and the fastest inflation is right where the bulk of the current seismic activity is located. Insar seems to be underestimating the uplift a bit, as it isn’t congruent to the gps data that we have access to but they both paint similar story. The new zone is rising at the rate of at least 8 cm/year and this time, the entire CCN complex is inflating. Whatever caused the swarm last year completely changed the volcano’s deformation, and the current swarm is centering around the most rapid inflation.
    Thoughts? (P.S No article until either something big happens or I get more information)

    • CCN is unlikely to erupt any time soon.
      It has been building up pressure for ten years, but so far it hasn’t been enough to break the lava dome. It will most likely be decades before we see anything relevant.
      The Cerro Machin volcano also had a similar story, but eventually calmed down.
      If not, based on the VC readings and all the data combined, I expect a Puyheue-style eruption in 2011.

      • I rather expect something like 1600 eruption of Huaynaputina. There are many similarities between these two volcanoes. CCN (like Huaynaputina before 1600 eruption) has reservoir of old dacitic magma, and hasn’t erupted since at least several thousand years.

      • Cerro Machin and CCN aren’t really that comparable,none of Machin’s swarms reached the intensity to just one CCN’s swarms. Since Nevado del ruiz is part of the same system as Cerro machin, so an eruption doesn’t need to take place at CM specifically for the unrest to verify.

  8. The HVO has started showing less than one Mag quakes on its maps. Some of the GPS stations near Kilauea are showing “Clean up” measurements approaching the levels around Sept. 2021, with CRIM lookin to be within 2 inches.

    Mac

    • The DI events often have a funny little jump in the recovery phase, a slight bounce and dip, after which the recovery continues but sometimes at a slower rate than before. In the past, there was often such a small bounce just before the onset of deflation. No idea why

      • By the way, when looking at these tilt plots on the HVO site, they are a bit out of date. But if you download the displayed profile, it gives the up-to-date one, not the one you were looking at. It is a mystery. Does Kilauea run off chatgpt?

  9. Explosions at Nevado del Ruiz is getting more intense, hopefully the proper measures have been put place in case a largish eruption takes place.

  10. Seismicity in the upper Southwest Rift Zone and summit of Kilauea keeps escalating. At this point, an imminent eruption is not unlikely.

    At the same time, we have the first earthquakes in the upper Southwest Rift Zone of Mauna Loa since the eruption, or at least the first that I’ve noticed, possibly the first small rock failure to the rapidly increasing pressure of Mauna Loa. Nothing imminent, but interesting nonetheless.

    • Today I have noticed that earthquakes accumulate in an area from the western border of Kilauea Caldera to Kilauea Iki (1959 eruption) and from this line towards the south.
      Which scenario is more likely: a linear fissure eruption inside Kaluapele (the whole Kilauea Caldera) like 4/1982 or a SWRZ (f.e. 1971)?

      1982 had in September a second eruption on the southern border wall of Kaluapele from where lava flew towards the SWRZ (it was the last eruption before Puu’Oo commenced 1983). It is judged as “summit eruption”, but can be considered as a semi-Riftzone-eruption.

      • The whole summit of Kilauea is quaking, really the next eruption might be from anywhere in the summit area, most likely still Halemaumau but far less certain now. I think it also wont necessarily be a long duration slow eruptio nagain either but a shorter eruption, liek the one a couple months ago, or even much less. There also might be a much larger summit eruption like 1959, with episodes and high fountaining, followed by a rift eruption, most likely to the southwest this time though.

        Really though, only the rift eruption is going to slow things down. If the eruption is at the summit, then pressure is only going to be removed very temporarily, and the amount removed will only decrease as the lake gets higher. So a rift intrusion in the next year is likely and very likely in 2024 at this rate, regardless of what activity happens in the summit.

        The SWRZ also has a lot of a’a, underneath the Observatory flows that came fro ma summit shield, basically all the lava surface is massive a’a flows, seems this is the style of eruptions here, fast and powerful, and at least sometimes of large scale. We have only seen this in 1974 but the ERZ was taking most of the action back then, nowdays it seems to be different. And Mauna Loa has deflated, so is probably not pushing that way anymore, and maybe wont for some few more years even with its own rapid inflation. It is going to be very interesting to be in Hawaii this decade.

        • This report shows the earthquakes before the 4/1982 eruption, the following fissure and lava flows: https://volcano.si.edu/volcano.cfm?vn=332010&vtab=Bulletin#bgvn_198204
          The eruption was close to Halema’uma’u, but on a line towards Kilauea Iki. It was preceded by several intrusions in ERZ and SWRZ. While the intrusions in ERZ may have been the pretext of PuuOo 1983, the intrusions in SWRZ may have been closer related to the 1982 eruptions.

    • It was not expected to do more then launch, anyway.
      So, Nice launch, and awesome explosion afterward! 🙂

    • This one is something like 5 or 6 versions out of date, only thing keeping another launch soon away is damage to the launch pad, it was just blasted with twice the power any other rocket has made, and was basically a block of concrete, probably also a test of how much support does it need where the answer is definitely more 🙂

      • Initial reports are that there is significant damage to the concrete underneath the launch pad and that a redesign of the launchpad will be needed to cope with the exhaust heat

        • I think that was an expected outcome, but it was also a test to see if a structure can survive under those conditions. Probably isnt well known but SpaceX has another launch site at Cape Canaveral, not the same as where they launch Falcon 9, and that site has been fitted with a landing tower and deluge system. To be honest I think the site in Texas was not meant to be a real launch pad, just a test for these missions, although probably not expected to be destroyed on the first go…

  12. Hey why is everything so quiet? So much unrest and yet so little discussion! In Chile, the massive and restless laguna del maule is producing it’s most intense swarm recorded so far in it’s unrest with magma ascension being the cause. In the beautiful yet debased lands of Alaska, 4 major volcanic centers are under some form of unrest, the most significant of which, Aniakchak, is rising at a speed of 3.7 cm/week. CCN is having it’s 4th swarm, the inflation has gotten faster, the hydrothermal system has gotten hotter, and the magma is getting shallower! Nevado del ruiz is getting more and more restless and a significant eruption is on the cards.
    Place your bets!

    • IMO Nevado Del Ruiz is the most likely to have a moderate (at least) eruption going forward, but that feels easy on account of how active NDR in comparison to the others.

      I do like Laguna Del Maule as a long shot for something major in the near future.

      Aniakchak will probably throw a 4 soon.

      CCN is either going to do something awesome (I’ll take an effusive event from a long ‘extinct’ volcano all the same as an explosive event) or continue to tease us for the next three decades.

      • NDV is the most likely to produce a significant eruption but if we’re takling about VEI 5+ eruptions, I am putting my bets on CCN first due to the constant escalating activity, Aniakchak is a good bet but the lack of major seismic activity weakens it’s immediate prospects. I think Laguna del Maule needs to do some more work before it gets to that point.

        • The problem with NDR is the risk of lahar if some of the glacier melts.

    • Laguna del Maule swarm has died down. I now think it was probably a gas-driven swarm, since it happened next to a well-known carbon dioxide degassing spot on the volcano. Inflation keeps going with no variation.

      The four Alaskan complexes are still quaking. But the intensity of activity has gone down in all of them throughout the past few months, with the only exception of Okmok, that is still making very low but constant levels of microseismicity.

      Regarding CCN and Nevado del Ruiz, I’m not very familiarized with where to find live information about those areas.

      • The decrease in seismic activity at the Aleutian volcanoes may just be temporary, as long as there is still deformation, there is a chance things will escalate. Got nothing to say for LGM…):
        Concerning CCN. things are complicated, The IGEPN released a special report about CCN after I made my comment about the anomalous deformation and we used different scans for different reasons. The SGC is superior when it comes to reporting and locating earthquakes but they haven’t released their report yet. Here’s my links if you want some more information
        https://www.igepn.edu.ec/tag/chiles?start=0
        https://insarmaps.miami.edu/start/0.7616/-77.7783/10.1381?flyToDatasetCenter=false&startDataset=S1_IW2_120_1182_1187_20170112_20230405_N00630_N00880_W078020_W077810_Del4PSDS&pointLat=0.79186&pointLon=-77.93864&startDate=20220214&endDate=20230405&minScale=-4&maxScale=4

        • Thanks. The links are interesting.

          My take is that a deeper storage under Potrerillos, of probably andesitic or basaltic-andesitic composition, is supplying a shallower storage, possibly dacitic, under the south flank of Chiles. This dacitic storage may have supplied the earlier activity of Cerro Negro and Chiles. The horizontal distance between the shallow source to either of the 2 stratovolcanoes is smaller than the distance between this source to the surface.

          If it erupts, I think it will probably by an effusive-dominated eruption. Construction of a large dacitic dome possibly hundreds of meters tall, dome collapses that produce pyroclastic flows, and short coulees of viscous lava more than a 100 meters thick. Similar to Irrupuntuncu volcano in the Central Andes, and probably similar to the earlier dome construction episodes of Chiles and Cerro Negro.

          An explosive eruption is also a possibility, in the VEI 5 to low end VEI 6 range. But I think is a less likely option.

          • As I’ve researched this volcano for 4 years now, I’ve come to understand that this is a very complex and interesting situation and as you know I expecting a more explosive eruption if CCN delivers on it’s unrest for a variety of reasons.
            First problem is that the geological setup is compressive and the current inflation may not completely represent the size and scope of the intrusion. The intrusion could actually be a substantially larger than the inflation suggests.
            The Second and in my opinion, the biggest problem is that we don’t definitively know how Potrerillos is related to CCN. Has the magma chambers merged? is the magma entering Potrerillos and going into CCN or vice versa? Where exactly is the intrusion taking place? What exactly is going on?
            The magma reservoir is large without a doubt, the inflation area is greater than 100km2 despite local limitations and on top of that, swarms of widely spaced 25+ km deep LPs have took place all over the complex including the NW corner of the Cerro Negro cone. Those LPs were like caused by magma movement at the deeper reservoir(See the monthly reports for Feb- Mar 2020)
            This volcano hasn’t likely erupted in over 100,000 years, plenty of time to evolve it’s magma and gain magma, build pressure, and clog vents.
            This swarm has my fullest attention, during the 2022 crisis, magma shallowed to 3km depth before stopping and now the current swarm is more numerous and more concentrated than ALL the other swarms in a with thousands of earthquakes confined to a single location, it looks like to me that either magma is on the rise once again or large amounts of magmatic gas is entering the hydrothermal system.
            I think there’s a deep felsic reservoir right under CCN that is feeding magma into a shallow chamber at Potrerillos and magma is trying to surface now to the south of Chiles. (Where the most quakes and fastest uplift is happening now.) Since all the volcanoes are plugged up I think the system is trying to make a new vent.

            Ultimately this just my hypothesis based on my research and I can’t confirm my propositions but in any case, we’ve got an interesting situation!

            .

          • I agree, it is an interesting situation. Most likely, the magma chambers of Chiles and Potrerillos are separate but connected. In InSAR, there are two separate inflation signals, which likely means two magma bodies. This is not like Yellowstone, where the whole 70 km caldera comes up like a balloon when it inflates. The earthquakes also suggest different depths. The Chiles body is about ~4-5 km underground. While the Potrerillos body is ~9-10 km underground. Earthquakes likely concentrate on the roof of the storages, along faults, or degassing pathways:

            The Potrerillos body must be supplying Chiles through an oblique conduit, is the most likely explanation I’d say.

            Chiles and Cerro Negro are small enough to have formed in single eruptions. There are many recent volcanoes in the Central Andes that have about that size and shape and are clearly monogenetic. So the Potrerillos-Chiles system probably has very un-frequent eruptions, I think effusive in nature.

          • I never thought of the possibility of Chiles-cerro negro being monogenetic volcanoes, that would answer some questions but in any case there is definitely deeper reservoir under CCN, https://www.sciencedirect.com/science/article/abs/pii/S0895981121001784 (It ain’t yellowstone sized)
            The reason why I am so skeptical of the second deformation signal being a shallow magma reservoir for the chiles cone is because we know that there is a hydrothermal system in that general area, we just don’t know how deep it is.

          • I guess it is the idea that a volcano of such size as to become an actual mountain cant be monogenetic, but that is obviously not true.

            Also that if a volcano stops erupting for 3 months then starts again it counts as a new eruption. I would bet that a lot if syratovolcanoes probably form mostly in one eruption, maybe lasting a couple hundred to a couple thousand years, with gaps of maybe a couple years but inconsequential over all. This might repeat in the same area more than once to make a much bigger combined structure eventually.

          • Not exclusively but for more viscous stratovolcanoes this might be the preferred method. Mafic stratovolcanoes probably form like Pu’u O’o did in the mid 80s, lots of lava fountains. This might apply to some andesitic stratovolcanoes too, like Hekla, where the melt is crystal poor or is not too evolved and flows easily.

            I guess it is maybe worth looking at the melt composition, given that most dome forming stratovolcanoes seem to be felsic but hiding that with mafic crystals in the magma to sway the whole rock to andesitic composition. Actual andesite magma seems to be much more fluid, a lot of basaltic andesites probably have andesite melt with mafic crystals but are free flowing. Crystal free mafic melts are extremely fluid, look at Kilauea and Nyiragongo 🙂

    • Unfortunately, those cameras don’t work in Chrome or Edge; I saw a note to use Firefox.

  17. Even before the last two eruptions I dont remember seeing nearly this many quakes, not until right before it breaks the surface and the intrusion has begun. But that is not the case, not yet anyway.

    The number of relatively big quakes east of the caldera around Kilauea Iki, and going down the SWRZ connector, that is very different to before, even only a couple months ago before the January eruption. Those areas would sometimes show smaller quakes but anything larger was only in the 2018 collapse and usually only right before. Perhaps this means nothing but something feels different this time around. Especially given how suddenly the last eruption ended, and then failed to restart a week later, and pressure has been building rapidly ever since.

  18. I have two favourite such volcanos.

    First is Graham Island. Also known as Ferdinandea Island and Julia Island…which reflects the next problem, which is the new island almost caused a four-war war! It appeared in the Mediterranean in 1831 to the NW of Malta and was immediately was claimed by four nations. Fortunately the island eroded away in six months, so everyone lost interest until the Italians claimed it on 13 November 2000 by means of scuba divers. All quite amusing.

    The second is Rangiroa in French Polynesia. The end state of a volcanic atoll – the volcano is long gone beneath the waves and the atoll is enormous.

    The best bit of Rangiroa is the French vigneron who built a winery on the tropical island. He gets two vintages per year! It’s the sort of old volcano that I really like.

    Vin de Tahiti

  19. Interesting read (as always), thanks! Last year I made a compilation of volcanic islands born since 1720, finding 48 island-building eruptions at 25 different volcanic centers, building a total of 63 islands (some eruptions gave birth to several islands). Of those 63, 45 have disappeared and 18 still exist.

    • Interesting! Islands that formed in eruptions from before 1720 but disappeared afterwards may need to be added to list of the lost. What did you do with islands that merged?

      • If you mean islands that were born as islands but then merged with land (such as Capelinhos for example), I still counted them as islands. If you mean islands that merged together, such as the Nishinoshima 2013 island, I just counted one more island-building eruption and one more island, even if technically there wasn’t one more island in the world after the merging occurred. The extreme case being the 2015 eruption of Hunga Tonga-Hunga Ha’apai, were the new island connected both old islands. So after this island-building eruption there was actually one fewer island in the world!

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