Two pillars sit at the end of the world. To the ancients, the entrance to the Mediterranean Sea was the end of the known (civilized) world. Mythology tells us that Hercules smashed the mountains to create an opening, flanked by two pillars. We don’t quite know which mountain was the southern pillar, but the northern one remains famous: the Rock of Gibraltar, still overlooking the ancient opening. It has a story to tell.
It looks out at the sea that keeps humanity apart. The very name means ‘Sea that divides the land’. The Mediterranean Sea forms a deep division between Southern Europe and North Africa. It wasn’t always: once this was a region with a common culture, tied together by the sea farers and their trading, in a Mediterranean melting pot of peoples and cultures. The sea has islands, volcanoes, high mountains and major rivers (well – two, to be precise, the Rhone and the Nile.) The deepest point is more than 5 km below the surface. And it has deep history. It binds west to east, north to south, and gave us the names of the The West and The East. It is so much more than a division. This sea has everything.
The most common name used by people living along it was ‘The Great Sea’ or just ‘The Sea’ as it is called in the bible. The Romans called it ‘The Internal Sea’, an appropriate expression as their empire covered the entire coast, north and south. Before that, in the heyday of ancient Middle Eastern cultures, this was the Western Sea (also known as the Syrian Sea). At a time when colours were used to designate directions, it was known as the ‘White Sea’ where white stood for west. (Black was north and red was south, explaining the names of the Black Sea and the Red Sea.)
The Mediterranean Sea is 4000 km long, equivalent to the entire breadth of the USA. One may wonder why it isn’t considered an ocean! The width varies from 2000 km north of Libya to 14 km at the Strait of Gibraltar. Some parts have their own names. There are 14 seas included in the Mediterranean Sea, such as the Aegean Sea. (The Sea of Marmara is sometimes included as number 15.) The number of islands is uncounted, but is at least 6000. The coast line and sea are shared among 24 countries and autonomous regions (including Palestine and Northern Cyprus), a long cry from the days of the Roman Empire. More than 150 million people live along its coasts. The world comes together around the sea that keeps them apart.
But amazingly, this enormity has only three narrow entrances. One of these has already been mentioned: the Strait of Gibraltar. The Dardanelles is even narrower, at 1.2 kilometers. And the third one is the narrowest of all and had to be dug by hand: the Suez canal. This sea of division is itself rather isolated. In consequence, it has very limited tides. The limited inflow from rivers adds to the difficulty this sea has. The Mediterranean Sea loses water to evaporation across the entire surface, amounting to around 0.5 meter per year. This is replenished through precipitation, river inflow, and flow through the Straits of Gibraltar in the far west. It takes a while before this circulation reaches the easternmost part where evaporation is highest. Because of this delay, the water level in the east is lower than in the west. Salinity at the surface is also a bit higher in the east. Replenishing the entire sea with Atlantic water would take a century.
Structure
The Mediterranean Sea is a complex jumble of ridges, plateaus and basins. There are continental shelfs along the coasts, in most places relatively narrow but larger along Tunisia and in the Adriatic and the Aegean seas. The plateaus are mainly found between Italy and Libya. Sicily and Malta share such a plateau, as do Corsica and Sardinia. There is a large, deep basin in the west, stretching from Gibraltar to west of Corsica. A second deep basin extends from east of Malta to Lebanon but it is broken up by many ridges and partly filled in by sediment from the Nile. A deep trough bends around Greece and Crete towards Turkey. Another trough runs within the Aegean Sea, an extension of the Turkey North Anatolian fault.
The structure gives rise to two main parts, the western and the eastern part, separated by a shallower rise connecting Italy to Africa. Thus, the Mediterranean Sea is a double sea, separated by a ridge. Compared to the simplicity of the Black Sea, this is a broken sea.
Volcanoes
Source: https://blog.navily.com/en/blog/the-mediterranean-volcanoes/
There are well-known volcanoes along and within the Mediterranean Sea. Italy has Etna, Vesuvius (where Pliny the Elder started the science of volcanology), but also Vulcano (whoever thought of that name?) and Stromboli. Greece has Santorini. But there are more. The ones we know well are just the ones that get their head above water.
An interactive map of the submarine activity can be found at https://maritime-forum.ec.europa.eu/contents/map-week-submarine-volcanoes_en. The hotbed of under-water volcanic activity is in the Tyrrhenian sea, between Italy, Sicily and Sardinia. The sea bed here is littered with domes, cones and mounts. There is a second field southwest of Sicily. A third field lies south of Spain but this is no longer active.
The Tyrrhenian Sea is home to Vulcano and Stromboli, both close to the coast of Sicily. There are many more below the water. Some, like Palinuro, nearly reach the surface. Palinuro contains some 15 separate cones. It may have formed short-lived islands during eruptions and would have been above water during the ice age. A tephra layer found in Italy has been attributed to an eruption of Palinuro 10,000 years ago. Marsili lies deeper but is larger: this volcano is considered larger than Etna. The mount is younger than Palinuro but it is not known whether it remains active.
Volcanic activity in the Tyrrhenian Sea appears to have migrated south over time. It is currently focussed mainly on the islands some 50 km of the north coast of Sicily. This group known as the Aeolian islands (including Stromboli and Vulcano) forms a small island arc: all seven are volcanic but only two are active.
The second volcanic field lies between Sicily and Tunisia. It is known as the Campi Flegrei del Mar di Sicilia (a descriptive name if ever there was one) and contains one larger permanent island, Pantelleria, and a smaller one, Linosa. Both are volcanic. (Lampedusa, nearby but close to Africa, is not volcanic.)
Pantelleria’s most recent eruption was in 1891. The event started in May/June 1890 with earthquake activity and uplift. After taking a year out, this was followed in October 1891 by much stronger seismic activity lasting 10 days, before an eruption started off the northwest coast. The eruption barely broke the water surface but it resulted in a phenomenon called ‘lava balloons’: meter-long, floating lava bombs. The eruption lasted for a week; the large size of the ‘lava balloons’ suggests that eruption rates were high. The eruption site was finally found ten years ago, as a young cone, 90 meter tall and reaching to 250 meters below the surface. The cone is located within a large volcanic field with many other cones, part of the Pantelleria rift.
Closer to Sicily are several other submerged volcanoes. The most curious of these is the so-called Nameless Bank (possibly the most google-proof name of any volcano!). There is also the small Terrible Bank and the much larger Adventure Bank. All three Banks are volcanically active. The last one is is also known as Empledocus, and is a large volcano with multiple eruption centres of which Ferdinandea is the most active. This vent has broken the surface several times since Roman history. The last time was in 1831 when it caused a major political row. In fact, this row still echoes on in the naming: Ferdinandea is also known as the Graham Volcanic Field. In 1831, an eruption here formed a new island. It is mentioned in a post on a mysterious island. The 1831 eruption appears to have been much larger than realized at the time. It led to the Sun taking on strange and unusual colours in various, distant locations. The island was quickly claimed by Sicily, France, Spain and England, and thereby acquired four different names. It was all in vain as the island disappeared again within 6 months. It still remains 7 meters below sea level – enough to create a shipping hazard. (It also very briefly re-appeared in 1863.) To avoid any recurrence of the territorial un-integrity, Italy has pre-emptively claimed the ephemeral island by dropping a water-proof flag and marble plaque. Neither survived long.
There is an another volcanic island arc in far east of the Mediterranean Sea, located in the Aegean Sea. This arc is much better known as it includes famous Santorini.
There is a bit of a pattern: the volcanoes avoid the deep western and eastern basins. They are active in the shallow regions of Aegean Sea and the Sicily Straits, and in the small Tyrrhenian basin. Each of the three region has a different causes of the volcanism, but these are clearly the geologically active areas.
Faults
Geology is a science looking for faults. And the Mediterranean Sea is full of faults. The map of the various fault lines looks psychedelic even in black and white.
The pattern of faults shows how complex the region is. Amazingly, apart from the westernmost region, Africa is free of faults. But the sea and the land to the north (Europe) are full of them. In simplified maps, there is often a single plate boundary drawn between Africa and Europe, bisecting the Mediterranean. The real situation is far more complex.
In the west, a fault surrounds much of the western basin, running through southeastern Spain and North Africa towards Sicily where it peters out. A second fault runs through the Atlas mountains also to Sicily, but passing south of the island and bends north into Italy and the Adriatic Sea.
In the east, several fault lines run along either coast, and there are fault lines in Turkey. Finally, the Mediterranean basin terminates at the Dead Sea fault.
Children of the Tethys
In the beginning was the Tethys.
(This is not entirely true, there was actually quite a lot that went on before it. But much of the structure of Europe and south Asia was caused by the dance of the plates of the Tethys ocean.)
There were several Tethys oceans, as far as oceanic plates are concerned. The ocean first began to form where China is now, like a slow Allemand at the start of the baroque dance movements. At the time, the continents were merged into a super continent, but this began to rupture in the east. It started as a large bay and grew to become an ocean. The southern part of the supercontinent moved away to become Gondwana while the ocean grew between it and the north. The Tethys ocean expanded westward. (Strictly speaking this was the Paleotethys, the ocean before what we normally call the Tethys ocean.) It finally reached the newly formed Atlantic ocean. But now it was becoming squeezed again as the south was on the move back. Oceans do not last forever: ocean crust eventually subducts, and the ocean plate moves towards its oblivion at the subduction zone. In the case of the Tethys ocean, the subduction zones were all at its northern margins, and the subduction pulled Gondwana back in. The world sped up in the Courante, the next phase of dance.
The Courante did not go smoothly. Rifting within the Gondwana continent would send parts of it north, to collide with Asia (and later Europe). The rift would create new ocean floor behind the continental fragment. So, the Paleothetys was superseded by the Tethys and later by the Neotethys. They all suffered the same fate, while in the process Asia and Europe acquired new land to the south while Gondwana became smaller.
Much of southern Asia and southern Europe are accreted parts – the remnants of the original Tethys ocean lie here. The Himalayas and the Alps show where some of the fragments docked. Each time an ocean was lost; and each time it reformed and was lost again.
After 70 million years ago, the Tethys began to close for good. An era drew to its close as the slow dance of the Sarabande played in the seas. But the ocean survived in the west, albeit with a fragmented oceanic plate. This became the proto-Mediterranean Sea. 20 million years ago it lost its connection with the east, overridden by the northward movement of Arabia. This left the proto-Mediterranean isolated and without a through-flow. Perhaps this situation will not last forever: the newly formed Red Sea, another re-incarnation of the Tethys ocean, may eventually reconnect to the Mediterranean and open it up to the Indian Ocean. However, so far has the Red Sea has fallen short.
The psychedelic tectonic map of the Mediterranean is a relic from its complicated history. Different parts have evolved differently. Continental fragments have jumped across, in a variety of places. In the west, the Balearic basin is surrounded by thrust faults. Further east, there are several subduction zones, starting with the Ionian Sea which is subducting towards Sicily. This is probably the cause of the volcanism in the Tyrrhenian Sea. Subduction around the Aegean Sea explains the volcanism there. The volcanism south of Sicily has yet another cause. This occurs on submerged continental crust (the ridge dissecting the Mediterranean). A graben or rift which runs parallel to the African coast indicates extension is on-going: the volcanism occurs on the thinned crust. Perhaps there will be future rifting, a young ocean crust will re-form and the eastern and western Mediterranean will reconnect.
In the far east of the Mediterranean, there is growing instability from the Turkish plate. It is moving fast towards the west, caused by Arabia moving north. The stress here is a consequence of the closure of the east-west oceanic connection in our post-Tethys word. The North Anatolian transform fault, accommodating this movement, is currently extending into the Aegean Sea, and moving towards the Greek main land.
This is the final dance, the Gigue, where everything quickens before coming together.
The Mediterranean Sea is a conflicted zone. North and south, east and west (black and red, blue and white) meet here, in a dance that has been going for hundreds of millions of years. Is this the end, the final movement? Africa continues to move north, albeit at snail’s pace of less than 1 cm per year. Eventually this should close the Mediterranean Sea and bring to a close the era of the Tethys: ‘Ruhe Sanfte; Sanfte Ruh’.
Plate movements relative to Europe. Source: Miramontes et al., 2023, Oceanography of the Mediterranean Sea, Chapter 2
But it may not. The Tethys has managed to avoid this fate before. It does so by rifting at its southern edge, creating a new ocean crust. Will this happen again? The only sign of any rifting is south of Sicily and it is very minor. Could it grow? Perhaps more likely, could the Red Sea finally get its act together and grow west, into the Mediterranean?
Crisis in the Med
Conflicts bring crises. The Mediterranean Sea has seen many wars around its shores. Even the Pax Romana did not bring lasting peace. But its biggest crisis did not come from humanity. It came from the Earth itself.
There is a fragility in the Mediterranean Sea. The lack of through-flow causes dangers. It has happened elsewhere in the Tethys, when parts of it became isolated and stagnant, but nowhere as serious as in the Mediterranean Sea.
The Strait of Gibraltar is crucial to the survival of the Mediterranean Sea. The water that flows through from the Atlantic Ocean keeps the sea alive: without it, the water level would begin to drop. There is also some inflow through the Bosporus and Dardanelles, channeling the water supply of the major rivers entering the Black Sea: the Danube, the Dniepr, the Don.
The flows go both ways. The inflow from the rivers and the Black Sea amounts to around 11,000 m3/s, the large majority from the Black Sea. The inflow from the Atlantic Ocean through the Strait of Gibraltar is around 600,000 m3/s. There is also an outflow through the Strait of Gibraltar which is nearly as much. The net inflow balances the evaporation rate which averages to 40,000 m3/s. But salt does not evaporate, and therefore the outflow must be a bit saltier than the inflow so that the Mediterranean Sea does not get any saltier.
The Mediterranean Sea is indeed saltier than the Atlantic ocean, and a lot saltier than the Black Sea. Saltier water is heavier. The inflowing water is lighter and therefore flows at the surface. On return, the saltier water flows along the bottom, through both the Strait of Gibraltar and the Bosporus. The inflow and outflow can happen simultaneously, one above and one below. It is give and take. But more water flows in than out, to compensate for the evaporation in especially the eastern Mediterranean Sea.
The Strait of Gibraltar contains a barrier around 25 km west of the narrowest part of the Strait, where the depth is as little as 100 meters. This is called the Camarinal Sill. Elsewhere it is deeper. There is a channel that is up to 300 meters deep and ends in the Gibraltar Trough, a 600-meter deep feature that connects to the Gibraltar or Alboran Basin, reaching 960 meters. The inflow and outflow pass through this channel.
Isolation
Image source Duggen et al. 2003, Nature, 422, 602
The crisis started in Spain. Around 7 million years ago, the region began to experience uplift. At this time, the Mediterranean Sea was connected to the Atlantic Ocean via two corridors, one north of the current Strait and one south. The southern one (the Rifian corridor) ran along the current Atlas mountain; it was the deeper of the two at some 700 meters. The northern channel (the Betic corridor) ran from south of Seville to Valencia. The Strait of Gibraltar did not yet exist: between the two channels was land. Whether there was also a direct connection to the Black Sea (or the Paratethys, at that time) is not known.
The uplift coincided with volcanic activity stretching across 500 km from southeast Spain to North Africa. This was not caused by a mantle plume: the volcanism was triggered by upwelling from the asthenosphere, the layer between crust and mantle. The precise cause is still under discussion. One suggestion is that the subduction of the old Tethys oceanic crust was rolling back westward, and that the upwelling filled in the hole. As the new material was much warmer than the cold oceanic lithosphere it replaced, the land was pushed up.
The evidence for the uplift can still be seen in fossil reefs in the region along the two channels, which are several hundred meters above sea level. As the land rose, the two channels narrowed. The Betic corridor may have closed as early as 6.3 million years ago. The Rifian corridor ceased to exist by 6 million years ago. A surprising consequence of this came 6.1 million years ago, when camels briefly appeared in Spain. Exactly how and when they crossed the remaining water barrier is not clear.
Water went in and out through the channels. But as the channels became shallower the return flow became impeded. Salt went in but not as much was able to come out. The Mediterranean Sea became saltier.
There had been signs of trouble for some time. Between 6.3 and 5.97 million years ago, plankton became gradually less diverse. This was probably caused by increasing salt levels. It is possible this can been traced back even to 7 million years ago. The outflow has gradually become more restricted.
Water can dissolve a limited amount of salt, before the salt begins to come out of solution. The crisis point was reached 5.97 million years ago, when suddenly, across the entire Mediterranean Sea, deposits of salts and gypsum began to appear. It seems likely there was a worsening of the situation at this time, perhaps with the outflow being further reduced. This would continue for the next 380,000 years. The gypsum and salt layers were not deposited at a constant rate. It was cyclical, with slowly increasing salt levels followed by a return to lower levels, and again a slow increase. There are 16 of these cycles visible in the deposits.
The saltiness (salinity) stabilized further during this time. It reached as high as 15% but did not go further, at least at this time. Gypsum formed, but halite, which forms under higher salinity, did not. There was still some regulation of salt levels, with the deposited salt and lost water being continuously replaced by the inflow from the Atlantic ocean.
There is a bit of a conundrum here. The stabilization of the Mediterranean Sea, albeit at a higher salinity, shows that it still continued to receive water from the Atlantic Ocean, and there must even have been some outflow of excess salt. But both channels had already closed, as far as we know. Models show there must have been a remaining shallow channel several kilometers wide, otherwise the salinity would have gone much higher. Which channel was this? (And would this not have kept out the camels? Perhaps the volcanic eruptions briefly closed the channel at times, with camels taking advantage of the opportunity. Speculation.)
It has been suggested that the inflow at this time came from the Paratethys or Black Sea. However, this could have replenished the water but not the salt as the Paratethys was only brackish. There must have been an unrecognized connection to the Atlantic Ocean.
The solution may be the obvious one. With the two main channels closed, the Gibraltar channel may already have existed and provided the missing link. It is really the only realistic candidate that we know about!
Gypsum was deposited mainly where the water was less than 200 meters deep. This suggests that the water was stratified, as is common in hyper-saline water bodies. At lower depth, the oxygen levels may have been depleted. The Mediterranean Sea was not a happy buddy.
Desiccation
This troublesome phase ended 5.59 million years ago, but not for the better. The second phase of the crisis began. At this time the remaining connection to the Atlantic Ocean was lost, whether this was at Gibraltar or elsewhere. Whether it was blocked completely or just severely restricted is a moot point: any inflow was no longer sufficient to keep up with evaporation. This may have happened intermittently before, but so far it had always re-established itself. Not so this time.
Little new ocean water came into the Mediterranean Sea. Rivers still brought in fresh water and rain would fall, but this could not keep up with the evaporation. Sea level began to drop at some 50cm per year. (Incidentally, this is similar to the rate as seen in the Aral Sea.) Within 1000 years, the sea would have been down by a staggering 500 meters, the surface level of the modern Dead Sea. All around the basin, the coast line receded. Rivers eroded deep canyons into the newly dry land. Any chance of a salt-water flow back towards the Atlantic ocean was gone: water does not voluntarily flow up-hill.
The precise cause of the blockage is not known. Worldwide, the cooling towards the coming ice ages had begun. As glaciers grew and declined, sea level fluctuated by as much as 50 meters. Part of the blockage may just have been from this. But the fact that it lasted so long suggests that there had also been a more lasting change in the remaining channel. One possibility is that the salt deposition was having an effect. It is similar to having an ice-age glacier lying on the land: the weight would have depressed the surface below, and thereby lifted up regions further out. Perhaps this isostatic uplift was the ultimate cause. Or perhaps an inconvenient volcano was to blame!
As the sea became saltier, new gypsum layers were deposited. Previous layers were now above water and became affected by erosion. Slopes became unstable and there would have been many landslides. These deposits are called the Resedimented Lower Gypsum (RLG) and they can provide a chaotic picture. The picture below shows such a deposit, found on Sicily. Earthquakes and tectonic activity became widespread at this time.
Source: Roveri et al., 2008, Marine Geology, 352, 25
And it did not stop there. The desiccation continued for 50,000 years. How far sea levels fell is not known. Some argue it did not fall much below 500 meters. Others find it could have fallen by as much as 1.5 or even 2 kilometers. In that case, only the deepest basins remained – everywhere else the sea became dry. Moses would have had no problem escaping from Egypt, although the journey across the salt-covered desert would not have been pleasant, or survivable. A recent paper argues for both, claiming that eastern Mediterranean went down by 2 km but the western basin only by 800 meters – the Sicilian barrier divides these basins, so they can evolve separately, depending on what inflow they could still get.
Two different views of the Mediterranean during the worst epoch of the crisis. Source: Krijgsman et al. 2018, Marine Geology, 403, 238
This was the heart of the Messinian Salinity Crisis. It is called that, by the way, after the geological epoch, which is named after the city on Sicily where Messinian salt and gypsum deposits are found – whether that means that the salt is named after the epoch or the epoch after the salt is an open question. The name was assigned to the epoch long before the Mediterranean crisis became known.
Halite began to be deposited, eventually reaching a staggering thickness of 2 kilometer in places. Halite forms in water with salinity of at least 35%: this extreme saltiness lasted for some 50,000 years. After that the Mediterranean Sea was unrecognizable. An arid phase followed with little rain: there no longer was a large body of water to provide a source of rain! The temperatures in the exposed regions would have been high. For every 120 meters of elevation, temperatures change by about 1C. At 500 meter depth, where the shoreline may have been for a while, it would have been 5C hotter than before. We can see all around us what just 1.5C of warming does. 5 degrees would have turned the place into an inhospitable desert. And the sea level even may have been as much 1 kilometer lower than this, tripling the heat. The surrounding regions would have been affected by the drought, the sand storms and the blowing salt. Times were not good.
This type of event has happened elsewhere. In fact we are ourselves have caused just such an event, though at a very much smaller scale, in another relic of the Tethys: the Aral Sea. But the Messinian crisis was off the scale. Over 400,000 years, over a million cubic kilometers of salt, 5% of all the salt dissolved in the world oceans, was deposited on the sea floor of the Mediterranean.
Lago Mare
The third phase of the crisis began when a ray of hope appeared 5.55 million years ago. The salt level of the remaining water reduced to below 35% – halite formation ceased. Fossil remains of fresh-water fauna have been found, suggesting the presence of lakes on the dry sea floor. Clearly, a new source of water had appeared. The most likely origin is the part of the Tethys ocean that covered the area around the Caspian Sea, the Paratethys. It may have started to overflow into the dry Mediterranean basin. This is the time of the ‘Lago Mare’, the lake-sea. The evidence is not fully consistent. Other studies find evidence for marine fish, which could only have come from an Atlantic overflow.
Overall, the indications are that conditions moderated. The climate became more humid. The water level stabilized, may even have gone up a bit, or may have fluctuated wildly – all have been suggested.
The Mediterranean Sea had gone through a deep crisis. But the worst seemed to be over. There were stirrings of life again. The three phases were like Bach’s famous Chaconne, the most emotional of his dances.
The mystery channel
There are major questions about the era of the Lago-Mare. How low did sea level go? (It may have been different for different basins.) What was the role of the Paratethys? And most of all, where was that mysterious channel to the Atlantic Ocean?
The depiction above is from Krijgsman et al 2018, Marine Geology, 403, 238. They have looked in detail at the various channels from the Atlantic Ocean. The Gibraltar region was a complicated one, with a variety of possible pathways for the water. But they find that most of those had closed long before the events. In the depiction, green indicates when the channel became dry land. Black means no data – erosion may have wiped out the layers of that age. The indications are that all channels had gone by 6.5 million years ago, with the possible exception of the north Rifian channel where no data has been found. After 5.3 million years ago, the modern Gibraltar channel is established. Before that, there is a lack of data on it. There is a good case that the mystery was indeed hiding in the open: Gibraltar.
The sea floor in the region shows an incision which runs for 300 km or more to the east, with a downward incline. It begins 20 km west of Tanger, well into the Atlantic ocean. The incision is filled with as much as 300 meter of sediment but remains identifiable. In the Strait, it splits into two branches, leaving the Camarinal Sill in between. The incision is around 2 km wide in the north arm and 4 km in the south arm. That is pretty much the size needed for the inflow during the early phase of the Messinian Salinity Crisis, and deep enough to provide for some outflow. Thus, it seems plausible that this is the original channel that remained active between 5.97 and 5.59 million years ago.
If so, the likely cause of the second phase of the Messinian Salinity Crisis is that the Strait of Gibraltar became blocked, and the third phase was help by a partial re-opening – perhaps just a bit of an overflow.
The Zanclean flood
The end of the crisis was spectacular. It happened 5.33 million years ago when the barrier at Gibraltar broke down and the time of the Lago Mare came to an abrupt end. It is called the Zanclean flood, after the geological epoch of that name. It is also the official starting gun for the Pliocene.
Geologically speaking, the change was instantaneous. There is no transition layer. Plankton re-established itself: the Mediterranean was a normal sea again with normal salinity. But in the deeper basins such as the Tyrrhenian, the recovery took much longer, perhaps 50,000 years. Even though the upper levels were normal, the deeper levels remained very salty, dense, and slow to mix with the healthier upper levels. This may have taken 50,000 years.
There is no mystery about the location of the new channel. The Strait of Gibraltar existed after this time, and it is the only candidate. But how fast was it? And what caused it?
One model is that of a sudden collapse of the Gibraltar barrier. If that were to happen with sea level in the Mediterranean basin 500-1000 meters lower, the event would have been catastrophic. The cascade would have quickly deepened its channel, allowing extreme flow rates. The whole sea would have re-filled within two years, with water level rising at 1 meter per day. This is called the Zanclean flood. This would fit with the 390-km long channel scoured into the Gibraltar Strait all the way to the Alboran basin, and to the 960-meter depth of this basin. This is the image that made the crisis so popular. Noah had nothing on this. A kilometer-tall waterfall with a flow rate of many times that of the Amazon river, who could resist?
But there are other models. One model suggest that there had been earlier inflows, and that the Mediterranean basin had already mostly re-filled, but step-wise. Another one suggest water levels were only a few hundred meters below that of the Atlantic ocean, requiring a far less dramatic flood.
The major uncertainty is in what the Mediterranean Sea looked like between 5.55 and 5.33 million years ago. Was it dessicated, with water limited to deep basing and lakes fed by individual rivers? Was it nearly full, with water only a few hundred meters below base level? Or was it fluctuating between these two, as some have suggested? The second option does not require a catastrophic flood event. We don’t know. The picture of the Zanclean flood is irresistible, too good not to be true.
The solution may be hiding around Sicily. In the second model, the Mediterranean is a connected basin, an ocean with islands. But in the first model, with water levels 1 kilometer below (or more), the sea is divided into separate basins, where the area around Sicily provides a barrier which separates the two halves of the sea. The western half would fill first in the flood, and then overflow into the deep eastern basin. That overflow should have left scars. Indeed, a deep, chaotic layer of sediment has been found here, but it is not accurately dated. So the Zanclean flood remains a mystery – or should that be a myth? Is it too good to be true?
Even in the mildest model, this was a spectacular mega-flood. Think 10 to 100 Amazon Rivers thundering through a corridor a few kilometers wide and cascading down 500 meters, lasting for years. The initial flow rate may have been as high as 0.1 km3 per second, flowing at speeds of 100 km/hr. Once the barrier broke down, erosion would have a field day.
What caused the reflooding? The cause is clearly in the Atlantic ocean. The global sea level may have risen higher than before, as the climate warmed a bit, leading to an overtopping of the Gibraltar block. Or the land may have become lower, either due to a tectonic adjustment or due to erosion. In either case, it would have been a long time in the making. The pressure of a sea that is a kilometer higher on one side of a barrier than on the other side is immense. If the land barrier weakened, for instance from a large earthquake or landslide, it could have failed catastrophically. A slow overtopping might have done something similar, causing a large waterfall on the far side which slowly eroded its way back – until the land could no longer withstand the water. Hercules saved our world.
After the end
In the beginning was the Tethys. Our world has been shaped by the Tethys ocean. It is an ocean that lasted for hundreds of millions of years, disappearing only recently. The Tethys has left signs of its past existence everywhere, from the basins of the Black Sea and Caspian Sea to the long mountain chains stretching from Spain to Myanmar. The Tethys ocean reformed parts of it many times. The Mediterranean Sea is one of those reformations. Perhaps it is not the last one: if the Red Sea eventually were to form an ocean it would have a claim to be the latest incarnation of the Tethys.
The extreme events that the Mediterranean Sea experienced 5.5 million years ago may have occurred elsewhere during the closing of the Tethys. Africa is by far the largest fragment that closed the Tethys, but did smaller fragments do similar things on a smaller scale? And continents have collided before, leaving us their ancient mountains chains. Did similar events to the desiccation of the Mediterranean Sea occur at those times? Plate tectonics can be a frightening dance. Humanity is not foremost in its mind.
Still, the earliest hominids were around when these events played out. Did they see the desiccated sea? Was Hercules one of them? We know not, but it is an interesting thought. Out of Africa – into the abyss.
The Rock of Gibraltar is still there. It is made from limestone that is far older than the Mediterranean Sea, but it is looking at a seascape that dates to the heady days of the Messinian Salinity Crisis. Here is the gateway that saved an ocean. It saved our divided world.
Albert, 25 December 2024
A more recent flood is described in Jokulhlaup in the English Channel
A bit of Mediterranean history can be found in And the sea was no more: the story of the Tethys marbles
From All of Us to All of You: Happy Christmas!
Optical Illusions
For Christmas entertainment, here are some images
Which colours do the balls have? Believe it or not, they are all the same colour.
A Christmas star: rays of light are seen emanating from the centre. But are they real?
Look at the image. How many dark dots can you see at the same time?
Tired of the endless winter Im stuck in …
Happy New Year Jesper! Since Decembre 21st the days are becoming longer again.
NASA gives us a nice overview of the ongoing Kilauea eruption using infrared imaging:
The accompanying article can be found here:
https://earthobservatory.nasa.gov/images/153767/a-fiery-display-at-kilauea
On the previous page, someone posted:
Looks like this place has a graben with eruptions along both of its bounding faults, the more serious activity (calderas, central volcanoes, etc.) mainly on the eastern one, significant population centers close by, and no rule of law. 🙁
Happy New Year VC!
Now up to 37 tremors of M4.3 or more in a week, with another 9 since yesterday. The place is just about continuously shaking.
In Iceland a M4 or M5 is fairly serious news, Ethiopia has had three dozen of them in a single week!
It would be pretty big news there, too. Most of the time the area is probably pretty silent at least reports are few and far between. Given this is a plate boundary it is probably silent until something breaks, both with earthquakes and eruptions. Fentale and neighbors might only go evety few centuries but then they all go in short order. The 1820s was ladt time so pretty neat 200 years it seems.
Kone was a productive caldera complex but might only be basaltic now given the recent basalts erupted in the calderas so presumably there is no rhyolite magma, so even a big eruption should be pretty harmless unless downwind. Fentale is an active central volcano though, it still looks mostly effusive but opening a vent is rarely quiet in such systems, so might still be a VEI 4 or even a 5 if there is a lot of magma involved, followed by lava effusion maybe a lot like Cordon Caulle in 2011.
And further southwest Boset-Bericha has young looking and extensive lava flows of both basalt and rhyolite on the same long fissure, probably over 1 km3 of both and erupted seemingly very fast (volume a rough guess probably a wide overestimate, but still) , and I wouldnt be surprised if it erupted 200 years ago too but no info.
The big lakes are all right in the middle, not all the calderas are lakes but I wonder if the calderas actually kind of form offset crom their deep source and towards the center of the major rift graben, maybe even with more than one deep source feeder. It always seemed like a VEI 8 caldera would either need one very powerful magma source (Yellowstone) otherwise it is basically multiple merged volcanoes. Toba is big enough to be 3 or 4 stratovolcanoes and seems to have at least 2 resurgent domes.
Corbetti is maybe on the small end to be considered a supervolcano but it is still a massive caldera and sits more central than most of the other volcanoes on the rift near it. It also might be a fully qualified supervolcano if it is the same as the Awasa caldera which is a VEI 8. Shala might also be close to that too, but not any of the others, and they seem to sit more on the sides.
Sucks there isnt a whole lot of information about this area in English. Even more when our species probably has been in this part of the world since the very beginning, some of these volcanoes might have affected our evolution more than most.
HVO moved the live cam so the fountains are visible now.
https://www.youtube.com/live/w0KulR_3wQk?si=eaK7MckSiivdaxj9
Seems there was a lot of overpressure in the summit to still erupt like this with the tiltmeter dropping so much.
Also nice view of slabby a’a flows near one of the webcams right now.
And still image
https://i.imgur.com/ptrBkUP.jpeg
These flows being a’a coukd mean the eruption rate us pretty high, not like on day 1 but more than steady state. Its likely there will be a pause again in the next few days, and maybe a longer gap of a few days to a week after this to recover. Im not sure if a longer gap would increase or decrease the likely intensity of eruptive episodes after.
The fountains are getting bigger, even visible above the rock in the foreground on the KW cam.
I wonder if, as the pressure is relieved by eruption, that nucleation of volatiles gets more intense and so causes bigger fountains before it stops. Either that or the eruption only stopped at all because of being drowned by the lava lake, it looks like a cone has formed around the vent so might be protecting it now and allowing the vent to mature and really grow.
V1 cam catches the lava fountains well:
The lava fountain seems to grow, maybe we get a nice lava fountain like during the early Pu’u O’o years?
Here we see one of the highest Pu’u O’o lava fountains 1984: https://www.usgs.gov/media/images/lava-fountain-450-m-1475-ft-high-pu-u-dark-plume-includes
?itok=fJ4cc_Im
The summit won’t probably be able to do this height, but maybe a 100-200m high lava fountain until the level of the Caldera rim would already be an extraordinary event in the summit area.
September 1984 was probably the month with the tallest lava fountains of Pu’u O’o: “the highest (460 m) fountains yet observed in the 1983-84 eruption” https://volcano.si.edu/volcano.cfm?vn=332010#bgvn_198409
The tallest fountain from Pu’u O’o was in June 1986, in episode 47 which was the last high fountain from Pu’u O’o. The fountain was sustained at 225 meters, but had peak measured height of 550 meters where it had a more explosive style near the end. Its actually unclear where that height starts too, it is probably calculated from the approximate base of Pu’u O’o which would still put this only just short of the 1959 record and possibly more reliable. But it might be measured from the vent, in which case the height is more like 700 meters above the surroundings. Its maybe no wonder the next episode saw the conduit fail and collapse…
This picture is from May 1986 episode 46, showing the same massive fountains, although this one wasnt measured.
How was Pu’u O’o able to create the high fountains 1984-1986? I imagine that they were the highest lava fountains in modern Hawaiian history. I’d suppose that very high lava fountains both need high liquid (magma) and gas pressure.
The Caldera Floor har risen to 940m by the growing lava field/lake:
How high are the current lava fountains?
Lava fountains over 100 meters at Kilauea are from vents that stay open and become mature. That is either by being long lived (1959, 1969, 1983-86) or by being low down abd forced open (1955, 1960). 1977 had a fountain to 300 meters too which might be an exception but only short lived. 1955, 1977 and 2018 fissure 17 were all evolved magma too so probably had higher volatile content to help.
But its basically because there is one vent, with lots of pressure. Fissure eruptions rarely do tall fountains until most of the vents close. If the vent stays open but the volcano builds pressure then what would have been a fissure eruptions is instead erupted from one hole and with huge pressure.
Kilauea Iki had “a maximum fountain height of 380 m”. That’s an impressive height for the summit. And Kilauea Iki’s “crater floor”, where the eruption began, has and altitude above the Kaluapele caldera. Kilauea Iki was one of the highest altitudes for a Kilauea eruption to happen … and with high lava fountain during first episode.
Kilauea iki had a maximum height of just under 600 meters.
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTWsTiJF_t1e_Y2L1Tlz_8aTVsEJD3161Ol4V67TOQnH-ISuh7mVYG6ZuA&s=10
The lava of that eruption was more primitive and unmixed, Kilauea didnt seem to have a huge and homogeneous magma system yet back in 1959, or the eruption shortly after at Kapoho probably would have been at least as big as in 2018. So its maybe less likely that we get 500+ meter tall fountains than it was in the mid 20th century but then its also still only barely over a week of this eruption yet, and the present fountains do seem very big for the lava output… 🙂
Also to note, Kilauea Iki vent was 1050 meters elevation, and Mauna Ulu before it became a shield was somewhere about 950 meters. Pu’u O’o in 1986 had build the vent up to close to 900 meters too. Not the vent is 940, so it is no more elevated than the others. If anything this spot might be stable the longest, filling in 100 meters of the caldera or even much more, its not filling as a full lava lake now, but as a perched pond overflowing, like a shield, so probably will build to 1 km elevation much faster than trying to lift the whole crater floor up to that point. To be honest if shield building starts the same as Mauna Ulu or Pu’u O’o, or Fagradalsfjall, its not impossible the vent ends up high enough to overflow southwest without filling the rest of the caldera, might only take 5 years or so even.
If this vent stays open abd can evolve into the same episodic repeating fountains then yes I would expect it to start getting big. Actually in theory the summit should be even better, most of the volatiles will still be there, CO2 is lost before ERZ eruptions but summit eruptions probably still have that to use.
Its also maybe dependant on if the vent can stay above the lake. The highest fountains at Pu’u O’o were when it filled in the early spatter cone crater near the end of 1984, without a lava pond over the vent fountains got huge but long lava flows also stopped and turned into wide a’a flows near the cone, a bit like at Etna but not quite as big.
It’s amazing how topography affects eruption dynamics. If 2018 had been 500 meters south–along the line of the 1955 eruption–Kapoho would still be in existence. If Kilauea Iki had erupted instead in Halemaumau, it would have resembled 1952 or 1967 and Halamaumau would be a memory. In the case of this eruption, the fact that a spatter cone or shield is being built allows the vent to remain (slightly) above the level of the lake.
If in 2018 the eruption had move a few kilometers downrift, it might have been difficult to evacuate Kapoho in time. HVO was probably on the case and might have been able to give early warning. But it worried me at the time.
Mauna Iki (SWRZ) erupted 0.04 km³ lava 1919-1920. With the current eruption rate, the volume of the present lava field/lake will soon get close to this number. Then the lava lake can become able to feed a Mauna Iki eruption again.
1919 it happened this way:
“In late November 1919, the long-lived Halema‘uma‘u lava lake stood at a high level, and in fact frequently overflowed onto the main caldera floor. Suddenly, on November 28, it drained away completely without earthquakes, leaving an empty pit almost 200 meters (660 feet) deep.
Over the next couple of weeks, lava returned and filled Halema‘uma‘u almost to the rim again. On December 15, an eruption on the caldera floor just southwest of Halema‘uma‘u produced a small lava flow. More significantly, surface cracks opened in a southwesterly direction outside the caldera to a distance of 10 kilometers (6 miles) down the rift zone.”
https://www.usgs.gov/news/volcano-watch-1919-1920-mauna-iki-eruption-kilauea-volcano
Volume of lava in Halemaumau is about 6 Mauna Ikis, 1920s was not as active as today just HVO was new and that was the first Kilauea flank eruption in 50 years. I do agree though that as the vent gets higher the chance that magma flows down the shallow crack Mauna Iki formed on will get higher, and all high fountain vents historically eventually failed by this exact method. It also happened at least once back in the early 19th century too.
I wonder if it will form a lava tube and make it all the way to the ocean, too. The Kau side if Kilauea is pretty steep and has less of a coastal plain where flows got stuck in the Pu’u O’o days. But then it does look like only 2 SWRZ eruptions in 500+ years have reached the ocean so maybe not good odds…
Yes. Maybe the years 1790 to 1840 have indeed more in common with our stage of Kilauea’s activity than 1919-1920. I’m just reading this https://pubs.usgs.gov/pp/1806/pdf/pp1806_chap2.pdf
The early eruptions had a high rate with >0.3 cubic kilometers per year 1823-1825. During this time both SWRZ (1823) and ERZ (1840) did eruptions with a much higher rate than any of the 20th century. 1840 the whole ERZ erupted from Alae to the lower ERZ. They “say with confidence that the 1840 eruption exceeds by a considerable factor the discharge rate of other Kïlauea eruptions.”
So it’s possible that the recent fast filling of Halema’uma’u and Kaluapele collapse craters will lead to fast and voluminous eruptions on SWRZ and ERZ that exceed the vitality of 20th century eruptions. But we can’t know what will happen when, how and first.
Etna only did Fumarole activity over Christmas
https://www.vulkan-etna-update.de/etna_update.html
But the Messinan Salinity Crisis by name also reminds to the risks for Messina quakes: 1908 around 80,000 people were killed by a severe earthquake in the Strait of Messina. It is an area with high risk for earthquakes and the worst “killer” threat for Sicily. The 1908 earthquake caused a 12 meter high tsunami.
A volcafastic 2025 to everyone!
Thank you! Same to you!
Hello all,
I think we must look at Fentale in Ethiopia.
A very large magma is going, rhyolic explosive eruption is possible
https://x.com/StormchaserNYC/status/1874168606726250741
Large ground deformation, uplift of 36 cm a week and 4 cm a day
https://x.com/juegongxinhai/status/1874412350713041214
For me we will have a mini flood basalt eruption like Laki in Iceland or even an explosive VEI 6 eruption because there are too much strong earthquake with over 40 M4+ earthquake a week. I have never seen this in my life. Before the krakatau 1883 and the Tambora ofn1815 eruption, there was a lot of energetic swarm.
It’s quitte worrying.
Oh snap!
Looks like there is a dike for sure but its maybe complicated in shape, interesting. Seems there is a spot north of Fentale that is deformed pretty shallow, might get a basalt eruption there. The other spot is right on the north side of the caldera and looks more rounded not a butterfly pattern of a dike so that might be where there is rhyolite.
Addis Ababa is fine, maybe some ash, biggest eruption maybe a VEI 5 lower end, the calderas arent super explosive except maybe when they are created. But rhyolite lava eruptions are rare and so are eruptions in this area too so its going to be interesting for sure. 2 intrusions in a few months and this much deformation, Fentale is 3rd on my 2025 eruptions list, right behind Kilauea and Sundhnjukur in that order, so its really #2 🙂
Evidence for Active Rhyolitic dike Intrusion in the Northern Main Ethiopian Rift from the 2015 Fentale Seismic Swarm
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GC008550
1.We report the first directly detected dike intrusion to occur in the Main Ethiopian Rift (MER)
2.The dike-induced deformation decayed exponentially (τ= 83 days) consistent with a relatively high viscosity peralkaline rhyolite magma
3.Magmatism in the northern MER is currently tectonically controlled in contrast to caldera-wide deformation in the Central MER
How explosive/effusive is the (possible) eruption going to be? Is it going to be a “mini flood basalt” event, a Plinian eruption or a mixed “lava and ash” eruption?
In case of a Plinian eruption, should we expect that NE winds push an Ash Cloud towards the west? There is the capital of Ethiopia not far away …
Probably an effusive rhyolite eruption, maybe explosive start of VEI 4. Basalt might erupt too if the dike is shallow enough beyond the area around the caldera, might be like at Sundhnjukur not as big most likely, but possibly longer.
Im not sure the viscosity is indicative of rhyolite. Kilauea had evidence of high viscosity magma in 2018 but it never erupted anything of the sort or likely has any significant volume of any magma that isnt basalt. Olivine crystal cumulate that is found under the ERZ and surely also in divergent boundaries would be a viscous fluid too, like wet sand is viscous even though water on its own isnt.
The rhyolite of Fentale seems not too viscous and pretty non explosive really, its not even really clear it has done an ignimbrite like some of its neighbors, might well be a gentle giant. Kone wasnt, it has many ignimbrite calderas and much bigger than Fentale, but its activity since the last ignimbrite up to now has been exclusively mafic so it is likely no longer silicic at all at least not right now.
Corbetti is maybe quite different, and it is too close to populated areas for any eruption of any sort to be harmless but still seems to be mostly effusive just much bigger in scale so still dangerous. It has massive effusive cones made if rhyolite and obsidian, like a kind of rhyolite shield volcano, although also a lot of tephra and one pyroclastic cone of Holocene age. Its a kind of irony that VEI 8 capable volcanoes are probably also some of the least explosive volcanoes, they need to be stable to accumulate so much magma. Just at some point it seems ok until it isnt…
Rhyolite is said to be less explosive than Dacite. If it degasses before an eruption, it may do some thick bright lava flows. Would it contain obsidian?
New Year Aurora
Space Weather Message Code: ALTK08
Serial Number: 49
Issue Time: 2025 Jan 01 1747 UTC
ALERT: Geomagnetic K-index of 8, 9-
Threshold Reached: 2025 Jan 01 1741 UTC
Synoptic Period: 1500-1800 UTC
Active Warning: Yes
NOAA Scale: G4 – Severe
====
Just caught a view myself but faded for now as Bz component of incoming magnetic field no longer so conducive but might change back at any time.
https://aurorawatch.lancs.ac.uk/
I saw the aurora out my bedroom window a bit last night close to midnight local time, 9.5 hours ago.
Fountain at Kilauea is going nuts.
The eruption currently does twin cones … like Svartsengi recently and Fagradalsfjall 2021 often:
https://www.usgs.gov/observatories/hvo/news/photo-and-video-chronology-december-31-2024-kilauea-summit-eruption
The lava doesnt look as bright or hot now, I remember seeing a picture of similar looking fountains from Kilauea Iki and it was when the vent was drowned but still able to erupt. It didnt do so for that long though, so I wonder if maybe lava is starting to flood the vent now too.
The lava lake rose to 943m, but sank by 3m later. Some lava appears to be draining back although the lava fountains continue:
The laser points to the middle of the crater where the lake from 2022 that I saw was. That part now is getting buried completely but I think it built up as a kind of pond that then failed. Unless HVO have saud otherwise the lava at the vents is probably higher than the range finder shows, maybe closer to 945 meters. If it was draining the lava would be flowing towards the fountains which it isnt.
It is fast filling, if it continues like this. The more the lava lake rises, the more area it needs to cover to rise again for 1 meter.
I’m finally catching up on my reading and that was an excellent article. About a month ago I had read an article about the flood-theory regarding the formation of the Grand Canyon and I have to agree that the mental image of that amount of water tearing across the prehistoric landscape is rather awe-inspiring and would be one of my first periods to visit and observe in any hypothetical TARDIS I might one day steal.
PS I am sorry for being so lax in pinning new-article synopses to the VC page on Facebook. The last two months have been a bit of a washout for reasons.
I wish everyone a happy 2025 or at the very least a lovely Wednesday.
Thank you. Happy New Year to you as well.
I read in one of Ron Blakey’s books that the Colorado Plateau and the coast in the south-west of the Unted States once, either during the early or middle Cretaceaus or in the Jurassic – have to check the precise time again – might have looked like the Namib.
Which means for me that one day deep in the future when subduction starts in the southern parts of the Atlantic the Namib might be pushed up like the Colorado Plateau and the Okavango and other rivers might create canyons esp. if there happens to be an ice age at some point. The American West is a picture book of what has been happening and will happen to Earth’ dancing plates and crusts. It has everything including terranes. Plus a long volcanic history.
The other side, the south-east of America+Eurasia (former Laurentia) in China has some stories to tell as well. The Colorado Plateau with the Grand Staircase and the Grand Canyon have 250 million years of earth’ history piled up in one place. And water plaid a role many times.
Impressive.
Just my eyes…Pele coming out of the side of the mountain?
Made an overlay of the interferogram of Fentale, as well as a quick map of the lava of its last eruption and those at nearby Kone and Bosat, which at least the former is dated to the same time. Rift is thin green line.
https://i.imgur.com/jHOfXqk.jpeg
To be honest, there is zero evidence of explosive activity at Fentale from its last eruption, and likewise at Kone. Bosat has some but its not large scale and its also unclear if it actually erupted in the early 19th century like the others. But the lava flows are pretty big, lava from Kone covered about 40 km2 in basalt over probably at least 3 eruptions, and Bosat made a sheet flow 9 km long and covering 13 km2 probably within hours if recent fissure eruptions like this are a clue. Fentale might have had a sizable basalt fissure eruption last time too, but lake Beseka has evidently risen and covered some of the flow. But flow ridges on a’a flows like this imply high eruption rate and thickness of the flow.
So perhaps some will be disappointed that this will probably be just another effusive volcano but that should also mean it is safer to actually take videos of it too should something happen. So far only Fentale has rifted and to the north not southwest, but its been only a few months yet. I doubt the events of past years before 2024 were proper rifting, not like this anyway.
It was mentioned on VD that the volcano closest to the area with most tremors is Dofen. Dofen is without a recorded eruption history, has erupted though at some point in the Holocene. It has a height of 1.151 metres.
Another volcano without a known history, height 1.745 in 1991 and before, is Bulkang Pinatubo.
About Dofen and volcanoes close to Dofen:
https://www.mountain-forecast.com/peaks/Dofen
Yes its up at the other end of the rift, theres a black lava flow and a cone on its north side but it otherwise looks pretty old which probably says something with how well lava is preserved for a long time in a desert.
The overlay shows that the southern end of recent deformation goes under Fentale, and I dont know if the picture would have cut off before Dofan if it was the parent volcano. Its not unlikely both are involved but I know which one I would bet on erupting.
Very strong (6.1) and rather deep (83 km) earthquake reported at South Sandwich Trench (SST).
An interesting area to watch might be Clearlake Volcanic Field, classified as High Risk by the USGS, last eruption 11.000 years ago, Geysers and Hydrothermal Plans, so s.th. like Campi Flegrei I guess. Latest quake near Santa Rosa, Sonoma County, Magnitude 4.7, Depth 1.1 km, 14 km south of the field:
There have been close to 1,200 shocks in the current sequence according to USGS. Even for the normally active Geyser thermal zone near Cobb, this level of activity is quite rare. Of note, this is the same area that experienced a similar sized shock immediately after the recent M7.0 HTJ shock a couple weeks ago (which as noted could have remotely triggered the Cobb quake)…and it would not surprise if this intense swarm has been amplified by the after effect’s?
Ugh. HTJ should be MTJ (Mendocino Triple Junction).
Home Reef volcano (Tonga) continues to expand its island. It reminds me to the expansion of the “reborn” Anak Krakatau after the collapse eruption 2018.
https://www.volcanodiscovery.com/de/homereef/news/261297/Home-Reef-volcano-Tonga-Islands-lava-continues-to-build-new-lava-delta.html
It already began to erupt in December: “the NE part of the island grew by at least 1,000 square meters between 7 and 12 December. The new lava had covered approximately 75,000 square meters by 15 December,” https://volcano.si.edu/volcano.cfm?vn=243080
The volcano behaves like Fernandinea: Sometimes an island, sometimes no island. A volcanic mystery island. I would exclude a HTHH event, but a VEI3 like 1984 can happen. Major rock type is Dacite … like Pinatubo and St. Helens, but in this case more friendly.
Just noticed a very high uptick in the number of EQ’s in Fantale Volcano. After years of no significant EQ’s they started in september/october of 2024, since the 27th of December they intensified. According to various postings, they expect an eruption. Any thoughts from the expert here what to expect?
There have been 2 swarms separated by nearly 2 months of quiet, each a basaltic dike intrusion, the second much larger. It’s the Krafla Fires, Manda Hararo, and ongoing Sundhnukur Fires all over again. But it’s likely to be mostly intrusive compared to Iceland cause the Ethiopian Rift is mostly intrusive when it comes to basalt. Expect more dikes in the coming months/years, if one connects with the surface close to the caldera then rhyolite will probably enter the conduit and come up, I wouldn’t expect anything too big if this happens, I doubt over VEI4, and more likely to be a low-intensity VEI3 with most of the volume going into a rhyolite flow. A normal basaltic eruption may also eventually happen along the rift.
This is apparently the 4th or 5th intrusion since 1981. I don’t really buy the idea that it’s rhyolite which means that it’s going to need to be high volume and gassy to erupt, likelihood is it will sojourn in the crust until it solidifies.
… and Iceland wants to do some pyromania again in late January: https://www.ruv.is/frettir/innlent/2025-01-02-likur-a-eldgosi-i-lok-januar-aukast-432131
“Likur” = Likelihood, “eldgosi” = eruption, “aukast” = increase
The longer the eruptions go, the more Icelandic we can understand.
Ha, I don’t even use the translate on vafri.is/quake anymore, got so used to it
Speaking of which, Ljosufjoll is at it again but with a couple of shallower ones, deep quakes are quite widespread though
Usually I can understand some single words (with help of skandinavian language knowledge) in Icelandic sentences, but not the whole meaning. The grammar and the “between” words like of / by / to / … make it difficult. Icelandic uses casus, where Norwegian or Swedish avoid it.
https://www.youtube.com/watch?v=a_zKjMrBHKo
Wow! the precipitation it looks flakey and looks just like snow is this wet snow on halemaumau summit? I think I have seen night frost on some of John Tarsons photos ( Epic Lava Owner ) grassy fields covered with white in a cold winter morning, but it coud have been night dew, it can get pretty chilly at halemaumau being a cool highland rainforest, and remebers reading rumours of wet snow in the 1970 s there during a chilly winter night
I’ve got a question for the caf:
What can cause a subduction zone to retreat?
This is mostly in the context of Italy/Apennines, but also the Sandwich/Scotia arc posted above has piqued my interest as it has retreated eastward.
Answers much appreciated.
Ocean floor moves away from the spreading centre, and begins to subduct when it gets too cold and dense, typically after 100-200 million years. If the ocean floor were to stop moving, then as it ages, the place where subduction happens will move backwards. More generally, if the rate of spreading of the floor is less than the rate of aging, than the subduction front will move backwards.
I am not so overly satified with the answer (pretty much an enigma to me as well) as the subducting plate is the South-American Plate, therefore a continental plate, maybe a bit similar to the New Hebrides and the Solomon Islands where the Australian Plate subducts. How dare they? It’s pretty confusing.
Sorry for that, hope you don’t mind. Enigma to me.
East of the crescent South-American Plate.
I think it is wrong in this piece (“The age of the subducting oceanic crust ranges from 27 million years old in the south to 80 million years old to the north. The East Scotia Ridge spreading centre cuts through the Scotia Plate from the northern part of the island arc, to the south forming the minor tectonic plate, the South Sandwich Plate.”)
https://www.volcanocafe.org/south-sandwich-islands-volcanic-arc-in-a-polar-climate/
and right in this piece:
https://www.volcanocafe.org/deception-island-the-phoenix-rises/
that might make you happier again.
You call it complicated. Every single paper I’ve seen about it uses the words complicated or complex. That’s what it is. Islas complicadas.
It was a generic question, with a generic answer how ‘roll-back’ of a subducting plate works. Every individual case has complexities. Only oceanic crust can subduct. The South American plate is like the Australian plate, it contains both continental and oceanic crust. The subduction you mention is of its oceanic crust.
Well. I’ve read up on this. There is something that led me and possibly many of us in the wrong direction. And that is the designation for the plates.
Basically all submarine parts (except very shallow ones) should have oceanic crust, otherwise they wouldn’t be where they are. They should be denser that the buoyant continantal crust that we see subaerial.
Then basically all the crust east and west of the MAR and west and east of the continental shelves should be new, “new” meaning up to about 100-120 million years old. It should have been formed at the spreading ridge like described here:
“Tectonic plates are created at mid-ocean ridges. As the plates age and move over the weaker asthenosphere below, they thicken and subside. Yet there are few high-resolution images of this process.”
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020GC009174
So, it leads to a certain confusion that they are called American/African/South American/Antartic etc. Plates. Basically they should either have their own names or be called like South-American Plate B=Oceanic Part.
This being said I would like to don to Andrew who asked the interesting question a comparable example:
Ryukyu Islands:
These are located on a small elongated Plate, the Okinawa Plate. East of it there is a convergent boundary with the Philippine Sea Plate (corresponding to South American “Sea”? Plate, with subduction creating the island arc, west we find the Okinawa Trough, a classical back-arc basin (corresonding to the sea west of the South Sandwich Islands), separated from the Yangtse Plate by a divergent boundary (spreading ridge), the Yangtse Plate corresponding to the Scotia Plate.
Hope that is so far correct. Next I will try to find out if every single island arc in the world demonstrates the roll-back phenomenon or not.
The answer might be yes, as the island arc forms together with the back-arc basin after a stagnation of subduction.
This is very pretty indeed, enjoy:
https://www.researchgate.net/figure/sland-arc-and-back-arc-basin-evolution-A-Subduction-of-slab-beneath-continent-without_fig1_253456332
Saved this. Too good to be true.
So, subduction is not like good sex with both parties being consensual 😉
The lady, often continental margin, is mostly unruly which leads to stagnation. You don’t need to post this although it’s harmless.
So basically the parts under the Atlantic Ocean outside the shelves should be called Atlantic Plate. If they weren’t oceanic they would never start a subduction process, but create mostly orogenies.
They will start to subduct though and might have started already in older parts with very old crust, hard to see as this would be submarine. In case we see anything subareal it would be La Palma. Lots of sediments around the Canaries.
They will subduct because the spreading will go on while the Pacific Ocean is becoming smaller. If both became smaller Earth would shrink.
As Planet Earth doesn’t shrink those oceans will stay in a balance. The Indian Ocean is subducting in Indonesia although this is debatable as this part could also be counted to the realm of the Pacific Ocean. Sumatra though can be counted as Indian Ocean realm.
To not make Héctor too annoyed – although Héctor is rarely annoyed – I should mention that there can as well be a mantle plume under the Canaries, and that Gran Canaria is about 10 million years older than La Palma. Tenerife is a little older than La Palma.
The ultimate proof for a mantle plume would be the birth of a new island west of La Palma though. I guess we here won’t see this, but maybe others if man is still alive.
Considering how negligently the media were talking about an escalation of that war in the east of Europe I am not so sure. Maybe they should all watch imaginations of the meteor impact 66 Ma.
The smaller vent at Kilauea stopped about 50 min ago, the episode might be coming to an end soon.
It collapsed in on itself.
Bit of seismic tomography over at Phys.org today.
Yellowstone’s volcanic activity is shifting to the northeast, geologists find (2 Jan)
Magmatic fluids and melts may lie beneath dormant German volcanoes (2 Jan)
Ok Yellowstone by now is becoming a cliche, but the graphic is nice. And the idea of a volcano erupting in Germany is interesting to say the least.
Interesting. One would expect Yellowstone’s focus to be creeping north-east as the US plate drifts over the hot spot. The historical trail matches. Thanks for the links!
Another Phys.org item answers the question of what volcano produced the ash of the unknown 1831 volcano:
https://phys.org/news/2025-01-year-volcanic-mystery.html#google_vignette
At least 30 homes have collapsed now and some of the locals are taking precautions. On a side note, local Ethiopian scientists are saying this likely tectonic activity. I have no idea where they are getting that from since this clearly is a dyke. Usually I’d be jumping up and down screaming for an eruption but if the local government is going to be so incompetent as to not even acknowledge what is clearly significant volcanic unrest, then it’s probably best for the magma to stay beneath the surface.
https://www.volcanodiscovery.com/fantale/news/261396/Fantale-volcano-update-Over-30-homes-reported-to-have-collapsed.html
Just reading that a dam might be concerned in the future (not yet):
” recurring earthquakes in Awash Fentale and Dulecha districts have caused widespread property damage, particularly in Segento Kebele of Dulecha district, where the Kessem Sugar Factory and Kessem Dam, with a capacity of holding 500 million cubic liters, are located. The area most affected by the earthquakes is Segento Kebele in Dulecha district, where the damage is extensive,” she stated. “The second most affected area is Awash Fentale district, where houses are collapsing day by day.”
https://allafrica.com/stories/202501020190.html
They are saying the Dofen volcano has erupted. The next to the north of Fentale. Denaliwatch may have been right to look at this volcano:
https://x.com/volcaholic1/status/1875137887160672670
I suppose the start of an alkali basalt fissure eruption?
Or rhyolite, I’m seeing a lot of domes, though the youngest lava is definitely basalt.
It looked like a mud volcano eruption. Something like the above-average hydrothermal explosive eruptions sometimes in Yellowstone, but on a mud volcano. Probably steam driven “passive volcanism”.
It’s putting out rocks so I’d go for a phreatic eruption at least
Hydrothermal explosions in Yellowstone throw out rocks like canon bombs. A Phreatic eruption (f.e. a Maar eruption) would contain cold ash made of crushed old rock (either old volcanic or sedimentary rock). A hydrothermal explosion is mainly clean white steam, while a phreatic explosion is more grey and dirty. But it can be difficult in some cases to distinguish.
A mud volcano – like those in Iran or Azerbaidzhan – erupts mud. As long as they erupt their typical mud, I’d judge them as the mud-version of hydrothermal explosions. If they erupt crushed rock as tephra, it’s phreatic.
The credit must go to Volcanodiscovery. They mentioned it first. I am only a precise reader. But thx to mentioning it, Héctor.
Looks like a mud geyser, not a lava vent. But pretty likely to involve magma at some point at either Dofen or Fentale or anywhere inbetween if this is any indication. There is a lot of water here, there might be risk of maar formation, although maybe not too.
Quotation from VD today:
Dofen (Ethiopia): A new vent producing a powerful jet of gas, rocks and mud has been observed at Dofen volcano in Dulecha district a short time ago. This is the area closest to the ongoing seismic swarm in Ethiopia’s Afar region, which we suspect to be caused by the intrusion of magma.
The embedded video below although not clear enough to see much details shows what might be phreatic or hydrothermal explosive activity, when ground water is heated by fluids from magma underneath and flashes to steam, escaping in this case from an open ground crack. It is not entirely clear if a vent had existed at the site before or if it opened recently.
There are no further details available immediately, but this clearly is a sign of escalation of the crisis and strongly hints that a volcanic eruption could be in the making.
https://www.volcanodiscovery.com/volcanoes/today.html
Basically, who became aware of the area first is Chacanger who also got it from Volcanodicovery, then Bruce of Newcastle and my humble self came in (page 1, comments) taking it seriously.
There was an explosive mud volcano eruption. Either tectonic movements or geothermal change has led to this reaction.
Last year of GPS deformation at Kilauea, with intrusions marked out. The first was at the end of January on the SWRZ, so was the second in early June and it erupted. The next 3 were in July, August and September, on the ERZ and the last one erupted. I noticed now that unlike the furst half of the year, there was barely any magma accunulation at the summit as it all went east. But each intrusion did break out at about the same point which I marked with a yellow line. that line was crossed a month ago with no 4th event.
Now, the current eruption occurred after another round of magma accumulation at the summit. The ERZ intrusions occurred in places with similar surface elevation to the floor of Halemaumau. So despite being a summit eruption, the summit is probably significantly overpressured. The first two episodes might be because the vent got submerged, where now it is a little different and the vent is more protected, and the fountains will continue as they are now for perhaps another week or more. Or, more exitingly, as the pressure drops volatile nucleation increases and fountain height does too. Until pressure at the summit gets high enough to push magma east, these fountaining episodes will continue, maybe until the vent gets to over 1000 meters elevation which could take months or even years.
Thanks for the synopsis Chad!
If it behaves like in 1800-1840, we may get some above-average SWRZ and ERZ eruptions during next 10-20 years. The very voluminous February intrusion in SWRZ is still there. If lava/magma from the summit intrudes there, we may get a big eruption like 1823. Also the summer intrusions in middle ERZ are still there. 1840 the very voluminous (with high rate!) eruption along the whole ERZ began without significant seismic signs, but was preceded by intrusions the years before.
The fast filling caldera means instability. We can expect surprises.
Current supply rate is about 0.2 km3/year, and the magma system is full. The area of the 2018 caldera is about 4 km2 area (rough guess) and 100 meters deep today, so could be filled by 0.4-0.5 km3. So the 2018 caldera could be filled to overflowing into the main caldera in 2-3 years although I doubt it will get that far in reality without escaping somewhere else.
0.2 km³/year is still higher than the eruption rate of Pu’u O’o with 0.11-0.18. This process can once lead to eruptions with higher rates than Pu’u O’o:
“Two early eruptions from the southwest rift zone
(1823) and east rift zone (1840) also had rates that
were much higher than those measured in any modern
eruption. Both eruptions were accompanied by rapid and
temporary draining of Kïlauea’s summit lava lake”
https://pubs.usgs.gov/pp/1806/pdf/pp1806_chap2.pdf
The location of the current position is where exactly the “volcanic SWRZ” starts. 2023 Hector explained SWRZ:
https://www.volcanocafe.org/kilaueas-triple-swrz/
“Eruptions from the northern strand of the SWRZ are fed from Halema’uma’u.”
The current eruption happens, where the eruptions are fed from, and it happens on the fissure line towards SWRZ (with Mauna Iki).
Its actually not in that rift, only close to it, but there was no involvement. The dike never went outside the caldera, but rather along the caldera fault or just stopped where the fissures did at the surface.
If I had to pick, now there is more info than 6 months ago I would expect the majority of eruptions outside the caldera to be on the ERZ probably near Napau like in September. But the SWRZ is closer to the summit, so while this summit eruption is going on and doesnt go east, a SWRZ eruption is reasonably likely. But really even HVO recently said that BOTH rift zones are presently in an active state and have increased eruption potential, getting them both is really rare, so right now is probably one of the most unpredictable times in Kilaueas recent history to predict its future behavior.
The early 19th century shows, that after the collapse 1790 the caldera filled quickly, and when the caldera was filled until the upper limit, the rift zones started to “explode” with SWRZ 1823 and ERZ 1840. Since 2020 we’ve observed the process of caldera filling. After 1790 the same process happened in the dark without valid observation.
The eruption cycles of Kilauea are probably not equal long. While from 1790 to 1823/1840 there were 33/50 years of “caldera filling”, we no have had only four years. It is possible that our witnessed period of “caldera filling” runs more quickly and ends more quickly than the one after 1790.
Chapter 2 in https://pubs.usgs.gov/pp/1806/ explains well the 1790-1840 period.
1823-1825 Kilauea had an eruption rate of 0.32 cubic kilometers per year. Pu’u O’o only had 0.11-0.18. The eruption rate decreased from 1825 to 1840, but 1840 it was shut down to very low level (at the same time Mauna Loa began to erupt more). Both the process of fast caldera filling and reaching the top limit of caldera limit caused the uncommon eruptions both on SWRZ and ERZ 1800-1840.
The last sentence should have been: “Both the process of fast caldera filling and reaching the upper limit of caldera filling caused the uncommon eruptions both on SWRZ and ERZ 1800-1840.”
Yohannes Haile-Selassie (grew up without parents btw) has been working in the Middle Awash area since he became a Paleoanthropologist,
https://en.wikipedia.org/wiki/Yohannes_Haile-Selassie
He found the quite a few specimen of early human ancestors there and further north, in an area called Woranso-Mille paleontological site, like this cranium (3.8 Ma):
https://news.umich.edu/a-3-8-million-year-old-fossil-from-ethiopias-afar-region-reveals-the-face-of-lucys-ancestor/
We get an idea what drove them away, at least part of them: Earth suddenly opening up, steam ghosts coming out of the mountains and finally throwing fire at them plus killing some with rocks.
They didn’t know what it was.
No family relation to Emperor Haile-Selassie (Emperor of Ethiopia from 1930 to 1974, the older ones of us still remember his name), Master and Ph.D. in Berkeley.
The Bone Hunter:
https://www.freshwatercleveland.com/street-level/CMNHHominids033121.aspx
Also interesting: John Gurche, Paleoartist, found by reading about Y Haile-Selassie
https://gurche.com/
Has achieved some impressive faces with emotions and a certain intelligence.
New article is up!
https://www.volcanocafe.org/domino-effect-in-the-great-rift-valley-dofen-erupts/