The Aral Sea

Here is the famous Steppe, the dry grass-land, the never-ending plain stretching across Eurasia from China to Hungary. Rainfall is too limited for trees to grow. The climate is harsh, with hot summers and cold winters. But this hostile land can make a good living for those who know where to find water. It was once a highway into Europe, used by the many invaders. Genghis Khan came this way. So did invaders of other types: the language, the apples and the horses. There are other steppes in the world. The American prairie is one; the South African veld is another. But none are as large or as famous as the Steppe. It is also known as the Great Steppe, but that distinction is not really needed. A single capital suffices.

The part of the Steppe between the Ural and China is known as the Kazakh Steppe. The historic trade cities of Tashkent and Samarkand are found here. Horses were first domesticated on the Kazakh Steppe, although precisely where and when is disputed: genetic evidence puts it as recent as 2000 BC. The climate here is dry, and the land in places verges on desert. It is kept alive by rivers coming from famous mountains to the south, the Pamir and the Tian Shan. These are among the tallest mountain chains in the world; their rivers provide corridors of water in a hostile land.

The Steppe and the Sea

Steppes of all kinds are found deep in the interior of continents. They are children of continental climates, far from the moderation and moisture from the seas. But water finds its way. Rivers in flat plains can reach dead ends, and form lakes. These lakes can grow to large sizes and attract life. The Kazakh Steppe contains many such lakes, from Lake Balkash in the east to Sarygamish Lake in the west and that ultimate of lakes, the Caspian Sea. A lack of outflow has left them brackish. And among them lies what is perhaps the most famous of the Steppe lakes: the Aral Sea. 400 by 300 km in size, it was once known as the jewel of Asia.

(When is a lake a sea? Size matters, of course. The Aral Sea is 300 km across. But Lake Balkash is 600 km long and did not get the upgrade. Both Aral and Balkash are saline, so that is not the difference. Lake Balkash is narrower, and in most places it is possible to see the opposite shore. The Aral Sea is also four times larger than Lake Balkash in surface area. But if those are the ultimate distinctions between a lake and an in-land sea, why is the Dead Sea a sea? It is only 15 km wide, after all, with a surface area 25 times smaller than Lake Balkash. The Dutch, with their love-hate relation with the sea, managed to turn one of their seas into a lake, twice as wide and twice as large as the Dead Sea, complete with the change of designation.)

(For those interested in trivia, there is one sea without any shore (the Saragasso Sea), and there are 22 seas (and one ocean) entirely devoid of water: look up and see the mares of the Moon.)

But in just the past 50 years, the jewel has lost its sparkle. The Aral Sea went from the third largest lake to a puddle and now to a desert. Only a few slivers survived in the largest ecological catastrophe of the 20th century.

The region

Image from www.worldatlas.com

Geography can be complicated. All this used to be part of the Soviet Union. When the Union collapsed, the area re-emerged as a collection of ‘stans’. The largest of these by far is the nation of Kazakhstan. It is the 9th largest country in the world and has become the buffer between Europe and China. To the south are Turkmenistan, Uzbekistan, Kyrgyzstan and Tajikistan. Together, these five nations share the Kazakh Steppe. The Aral Sea is on the border between Kazakhstan and Uzbekistan. It is also midway between Russia and Iran, and between the Caspian Sea and China.

Source: Plotnikov et al Zool Stud. 2023; 62: e19. 10.6620/ZS.2023.62-19

The Kazakh Steppe is bordered to the south by large mountain chains: the Tian Shan (’Heavenly mountains’) in Kyrgyzstan and China, and the Pamir mountains in Tajikistan. The Kopek-Dag mountains in Iran and the mountains of northern Afghanistan complete the southern boundary. The Kazakh Steppe forms a lowland against these mountains. To the north the land rises again to become the Kazakh Uplands.

(There are no volcanoes in this post. If you want one, the nearest major volcano is Mount Damavand in the Iranian mountains south of the Caspian Sea.)

The lowlands are not a continuous band but are divided into several depressions. The area north of the Caspian Sea is called (of course) the Caspian depression. The Aral Sea is located in the ‘Turan Lowland’ or ‘Aral Sea Basin’ which stretches from close to the Caspian Sea to the Tian Shan mountains. Lake Balkash lies in a separate depression. Tectonically, the Caspian depression and Aral Sea basin are part of the same structure but with an internal watershed.

Source: The Aral Sea: A Story of Devastation and The Aral Basin. Source: Partial Recovery of a Large Lake. Philip Micklin et al., 2020

The local climate is dry. Annual rainfall amounts to only around 100 mm, making the region of the basin a semi-desert. Winters are cold, summers hot, and rain mainly comes from showers in between these seasons. There are only two major rivers in the region: the Persian names are Amu Darya and the Syr Darya. (As you may guess; ‘Darya’ means river; the names are sometimes written as one word.) The names are recent: the Amu Dary was originally known as the Oxus and the Syr Darya as the Jaxartes. These are the two largest rivers in western Asia. The Amu Darya comes from the Pamir mountains, with two sources on the border between Afghanistan and Tajikistan. It flows over 2,500 km in length and is the longest river here. The Syr Darya comes from the Tian Shan mountains, with a source in Kyrgyzstan. Alexander the Great complained about this uncrossable river: it became the border of his conquests. The rivers benefit from the high snow-rich mountains, but the water flow is dependent on the amount of snow and varies from year to year.

Both rivers flow into the Turan lowland and into Aral Sea. No river flows out from this basin: it is the rivers’ final destination. This imbalance is the main reason for the existence of the Aral Sea.

A Sea Oasis

Fishing on the Aral Sea, 1952. Source: https://m.cdn.blog.hu/ri/ritkanlathatotortenelem/image/aral_to/muynak1952_kicsi.jpg

The rivers feed the same large body of water at their terminus, though with different entry points. The original Aral Sea is (or was, around 1960) a brackish-water lake covering an area of 67,499 km2 with a water volume of 985 km3. 75% of this water came from the rivers: they brought around 56 km3 of water per year. The spring and autumn rains into the lake (130 mm per year) added 9 km3. Evaporation of 66 km3 balanced the water level. The high evaporation (in summer) and lack of outflow made the water brackish; the salt levels are about a third of that of sea water. The sea is not particularly deep: typically 10-20 meters only. The name ‘Aral’ refers to the multitude of islands which stuck out from the shallow sea: ‘Aral’ means island.

The Aral Sea, 1960

The Aral Sea contains four separate basins. The main area of the Sea forms a shallow basin. On the western and northern edge are the deeper west basin, a small northwestern Tsebasch basin and the northern basin. The western basin is 60 meters deep. As the region is only around 50 meters above sea level, this puts the bottom here below sea level. The Amu Darya enters from the south into the main basin, and the Syr Darya flows into the northern basin from the east.

The semi-desert around the Aral Sea is inhospitable and sparsely populated. The novelist Andrei Platonov describes it as ‘a land that is pale and salty, as if its tears have dried but its grief has not run its course’; he also calls it ‘the hell of the whole earth’. Obviously, he did not like it! This is the Kara-Kum, the red desert. But the Aral Sea was different. It teemed with life. There was a vibrant fishing industry in towns such as Moynaq, on the southern shore, where some 30,000 people lived, and Aralsk on the north side of the sea. Fishermen would go out for days to collect their catch: sturgeons, trout and beams, among some 20 different species. A 6th of the fish eaten in the Soviet Union came from here. In the 19th century, the Russian navy had a base on the Aral Sea, although they found it difficult to get their ships on location. Maybe that is what really differentiates a sea from a lake: a navy.

Ships on the Aral Sea. Taras Shevchenko, 1948 (source: wikipedia)

Where the rivers flowed into the Aral Sea, fertile deltas build up. These acted as oases in the semi-desert, with lush growth and an abundance of wildlife. Caspian tigers occurred here, living off the wild boar and bactrian deer. This subspecies of the Siberian tiger lived along rivers and lakes, and ranged from China to Turkey, the widest distribution of any of the tiger subspecies. One specimen, not fully grown, was shot in 1949 near the Aral Sea. It was probably among the last sightings of tigers there. Its stuffed remains were for a while on display in a museum in the city of Nukus. Tigers remained present further south along the Amu Darya until the 1960’s. They may even have survived in eastern Turkey until the 1990’s. The Caspian tiger was declared extinct in 2003.

The Aral Sea was an oasis in the Steppe. But it was a fragile one. And the Kara-Kum was waiting.

The vanishing sea

Going – going – gone

The Soviet Union had other priorities than the environment. This started early: already in the 1930’s, Vozrozhdenya island (the largest island in the Aral Sea) was used for secret bioweapon development. This started with open-air experiments, before building a contained facility. The idea was that if containment was broken, only the island would be affected.

Then came the white gold of cotton. The Soviet Union decided that cotton was the future. For a while, Uzbekistan was to produce more cotton than any other country in the world. But cotton is a thirsty plant and the Steppe is dry, not well suited to such a crop. In the 1950’s, plans were made to use water from the two major rivers for this purpose. A canal was build to divert the water of the Amu Darya, with predictable (and predicted) consequences: after 1960, water flow in the Amu Darya suffered. Water from the Syr Darya also ended up in large irrigation lakes. Inflow into the Aral Sea decreased, but evaporation continued and now the water level the Aral Sea was beginning to drop. Because the sea was not deep, small changes in water level quickly lead to large changes in area. The port cities saw the sea withdraw from them.

This had been expected: cotton was seen as more important than fish. But to the locals, it was bad news. Already in the 1950’s, it was known that the Aral Sea would change and at the least become more saline. New fish species were introduced in the mid 1950’s – whether to safeguard against the coming changes or just to diversify the fishery is not clear to me. The introductions even included baltic herring, but that was a change too many. The herring was too prolific, eating all the plankton and then dying from lack of food. Other fish species, such as the black carp, were more successful and in the 1960’s displaced most of the native fauna. Eventually, this preparation would be in vain as the sea’s decline continued unabated.

At first, the falling water level was managed by mooring the ships further from the original shoreline. There were still fish, and catches were fine. The harbour at Aralsk fell dry but the jetty could be made longer. This all changed in 1976. In the mid 1970’s, fresh and brackish water species disappeared. A few years earlier the water had become too saline for the young fish, and now the lack of reproduction reached the mature fish population. A local fisherman recalled how the catch suddenly collapsed in 1976 and 1977. And by 1979, a new problem arose. The fish was taken by transport ship from Aralsk to the factory in Moynaq but the sea had become too shallow and the ships could no longer get across. Five years later, the level in the Aral Sea had dropped 12 meters. Large areas were becoming dry and the fishing industry was dead. By the end of the 1990’s, there were no fish of any kind left in the Large Aral Sea.

The falling levels had another unwanted consequence. People were getting too close to Vozrozhdenya island. In August 1971, a marine biologist from Aralsk was studying the plankton. She suddenly became ill with high fever and a rash, and later bleeding sores. Her young brother too fell ill and so did his school teacher. The marine biologist died. Only now was the disease diagnosed as smallpox – a variant that had been tested at Vozrozhdenya island. The entire town of 40,000 people was cordoned off and everyone was vaccinated. This instant response worked: only a few more people contracted the disease, though two more died of it.

The water levels kept falling and more and more of the sea fell dry. Only now did the Soviet Union report on the situation. Earlier it had been kept secret, in a country were internal disasters, such as airline crashes, were never reported. When perestroika came in the mid-1980’s, this changed. But the new openness did not change the lack of water: in some years the Amu Darya dried up before reaching the Aral Sea. In 1987, the northern part became separated from the main basin. By 1989, the Aral Sea had halved in size, mainly by contraction of the southern and eastern shore. By now the sea had fallen so low that the islands became peninsulas. By 2010, the water level had dropped 30 meters; the Aral Sea had become divided into several separate lakes. The main Aral Sea became reduced to a small central area which in 2014 dried up completely. Only the deeper basins along the western and northern edge still held water.

Source: The Aral Sea: A Story of Devastation and Partial Recovery of a Large Lake. Philip Micklin et al., 2020

The decline is nicely illustrated in this NASA article. In wet years the main basin contains shallow lakes. In dry years, it dries up completely. The rest of the sea consists of several isolated bodies of water, one for each of the other three basins. The western basin has become saltier than the sea and little life is left in it.

The climate in the area changed, not surprisingly. The summer is now hotter but winter frost lasts longer and the growing season has shortened. The dry sea bed has left salt deposits, which are blown by the wind. This is badly affecting the health of the local people, not helped by the pesticides that also ended up in the lake.

Recovery

For a while, a plan was consider to divert water from central Siberia to here, but this was abandoned in the mid 1980’s. In the 1990’s, as the Soviet Union collapsed, new plans were made to save the sea. This coincided with a time of reduced irrigation (due to the economic collapse) which for some years stabilized the water levels – but they started falling again when the economy recovered. In the year 2000, only 2.5 km3 of river water entered the Aral Sea, almost all from the Syr Darya. Although evaporation had also decreased (due to the much smaller surface area of the sea), saving the entire Aral Sea was not possible. Instead, efforts focussed on the northern part, the Small Aral Sea.

In 1992, a dike was build across the outflow channel that connected the higher Small Aral Sea with the remnants of the Large Aral Sea (the main basin). The Syr Darya now fed into the northern part only. This failed dramatically in April 1999 when the Small Aral Sea overtopped the dike during a wind storm, and the dike was swept away. Two people who had been trying to repair the dike were killed in the flood. A larger and better dike was built, called the Kok-Aral dam, which was ready in 2005. It has kept the water level in the Small Aral Sea at 42 meters, which is 10 meters below the 1960 level. In good water years, excess water is fed into the Large Aral Sea.

The Kok-Aral dam

The Small Aral Sea settled at a salinity similar to that of the old sea. Fishes returned, having apparently survived in the Syr Darya or in some cases, were re-introduced. The Aral salmon was lost for good, sadly. Total catches are now 5-10 times lower than those of the old Ara Sea, but it provides a living. Kazakhstan has considered building a second dam within the Small Aral Sea, to raise the water level further in the bay at Aralsk and allow use of its old harbour.

The highly salty western Aral Sea (the Shevchenko Gulf) is now used for brine shrimps. This species was introduced because it could deal with the very high salt content, and brine shrimp eggs are used as fry food in fish farms. The processing company remains located in Moynaq, 200 km away, which means long treks in four wheel drives across the salt plains. The fish processing plant here now imports its fish from Russia in a dubious feat of economic planning. (Aralsk now has its own processing plant.) There is a little tourism. Moynaq is known for its ship cemetery where some of the rusted hulks are left to decay: many of the photographs of dying ships are taken here. But the ships did not get stranded here: they died elsewhere and were taken back.

Moynaq’s ship cemetery

There are no plans for full restoration of the Aral Sea. The recovery will instead remain focussed on the Small Aral Sea which falls fully within Kazahkstan.

The Large Aral Sea and its surroundings have become the newest desert on Earth. It has become known as the Aral-Kum. Instead of recreating the Aral Sea, Uzbekistan has created a development plan for the region, aided by the World Bank. Food production remains its priority, in conflict with the needs of the Aral Sea. An attempt is made to plant saxaul bushed in the dry sea bed, to stabilize the soil, but as yet this is limited to a 500-hectare demonstration site. And since 2022 Afghanistan is building a canal to divert 20% of the Amu Darya, making it even less likely that the Large Aral Sea will ever return.

And there may be problems coming for the Small Aral Sea as well. Flow in the Syr Darya is decreasing, as more and more of its water is used along the course of the river. There is no guarantee that even the Syr Darya will continue to reach the Sea.

Some life has returned to Aralsk on the Small Aral Sea, but elsewhere the signs are not good. The Sea will not dry out completely: at the very least the rains will still fall. But this will only be a hyper-saline remnant.

The flat, dry sea bottom is covered in sea shells, with sparse bushes in the dessicated landscape. Salt is everywhere. Even the camels die from eating the salt-covered vegetation. Young people show stunted growth, caused by the pesticide-laden sand storms. Global warming is now adding to the pressures in the region. Sand dunes are approaching from the south and are covering the old, abandoned towns.

Condemned to repeat

Those who forget the past are condemned to repeat it. It turned out that the Aral Sea had always been an unstable entity. Its water armageddon has happened before.

The water flow in the rivers is very sensitive to climate – even when both rivers feed into the Aral Sea, the amount of water is not guaranteed. Fluctuations in water level of the Aral Sea by a few meters were not uncommon, and much larger variations have occurred. The decades before 1960 were, in hindsight, more stable than usual. When the Aral Sea dried up, old river beds of the Syr Darya appeared on the sea floor, a sign that the water once had been much lower than in 1960. This has in fact happened more than once, even in the fairly recent past.

In the northern part of the Large Aral Sea, ruins of old settlements appeared, some 20 meters below 1960 water levels. There are three, called the Kerderi cluster, dated to around the 14th or 15th century, and having lasted around 200 years. Although there is little left, the remains include two mausolea with ceramics and mosaics: this was a significant settlement, perhaps involved with the silk road. A document from around this time (1417) comments that the Amu Darya flowed into the Caspian Sea and that the Aral Sea had ceased to exist. That overstated things: the presence of settlements suggests water remained, but at a much reduced level. The Amu Darya was said to have returned to the Aral Sea around 1573. By 1700 the Aral Sea is depicted on maps at its current (i.e. 1960) size. The low level would have lasted from around 1200 to 1600.

And this had happened before. Before the 6th century AD, the Amu Darya also ran towards the Caspian Sea and the Aral Sea was much lower. This lasted perhaps 500 years.

The cause was in the high mountains. Both rivers carry sediment from the mountains, and this becomes deposited on the flat plains of the Aral Sea Basin. It silts up the river bed, forcing the river to change course. Especially the Amu Darya is affected by this. Just a small change in its pathway can cause it to miss the Aral Sea entirely and instead flow into the Caspian Sea.

The Aral Sea was always precarious: its level varied dramatically with the course of the Amu Darya. The Syr Darya was more reliable, as shown by the fact that it produced river beds at these times while the Amu Darya did not.

In fact, before around 2000 BC the Amu Darya may not have reached the Aral Sea at all. Without the Amy Darya, the Aral Sea would have been much smaller or dry. This had lasted for many thousands of years. There was only one reliable river (Syr Darya) flowing into the Aral Sea. The Amu Darya was always a much more fickle entity. And the Syr Darya only came some time after the ice age: before that, it went into a different direction.

The ‘modern’ Aral Sea seems to have been a relative recent development. The Aral Sea was perhaps the world’s youngest sea, dating only to the middle holocene.

Before time

The Caspian Sea and the Aral Sea are separated by a watershed which is only a few meters higher than the 1960 water level. Water levels in the Caspian Sea were particularly high at the end of the ice age, high enough to overflow the watershed. At this time a huge body of water connected the two seas. This overflow may be the reason that the fauna of the two seas were quite similar.

And this had not been not an isolated occurrence. During the late pliocene (from some three million years ago), the Aral Sea was mostly an extension to the Caspian Sea although it did dry out at several times when the connection was lost. The ice age was dry, until the melt temporarily re-established the large sea. Once that ended, the Aral Sea had to wait for the rivers to establish themselves.

The Tethistan

We mentioned how the Caspian depression and the Aral Sea Basin form a huge low-lying area. But why is this basin here? To the south are the enormous mountain ranges, in places 7 km tall. To the north is the Siberian plateau, typically 500 meters high (and covered by the Siberian traps, but that is a different story). In between is this low-lying land, close to sea level at Aral and as low as 200 meters below sea level in the Caspian Sea.

Looking at a map of the continent, a series of water-filled depressions show, from the Black Sea to Lake Balkash. It is much shorter and not quite as recognizable as the line of mountains from Spain to Thailand, but it shadows this line. If these mountains are the scar of the Tethys ocean, the line of lakes and seas are the accompanying itch. We are in the shadow of the Tethys.

Once, the Tethys divided the world between north and south. It was home to a progression of continental cast-offs from Gondwana in the south which crossed the sea towards the north. When they arrived, each would dock at far too high a speed (have you ever tried to stop a continent moving at 10cm/year?) and would raise a crumple zone. Hence the mountains – each of the chains which make the line come from a separate collision, all part of the complex closing of the Tethys ocean. The Tian Shan formed from an old suture (from the merging of the Tarim plate of China with Siberia, 300 million years ago), re-activated by stress from India, 40 million years ago. Mountains further west come from other additions to Eurasia. Each of these contributed to the slow demise of the Tethys ocean until it finally ceased to exist 5 million years ago.

Source: wikipedia

In the process, the various collisions divided the Tethys ocean. One part is called the Paratethys: it sat north of Turkey around 30 million years ago. The past existence of the Paratethys was recognized already in the 19th century, as the remains of an ancient Mediterranean stretching from Crimea to the Aral Sea. Nowadays we make it even larger. The Paratethys became isolated from the main Tethys ocean some 15 million years ago and slowly disappeared.

The disappearance left the deep salt deposits of eastern Europe, as far west as the appropriately named Salzburg. The lively salt trade of medieval Europe is based on the inheritance from this dying ocean. But as for its water, the only seaworthy survivors were the Black Sea, the Caspian Sea and the Aral Sea.

Don’t expect oceanic crust here: this was mostly a shallow ocean from submerged continental margins. Only the Black Sea and the southern Caspian Sea contain some true oceanic crust – among the last remnants of the original Tethys Ocean. Elsewhere are a number of separate continental blocks which underly the basins, each with their own origin. What they have in common is the Paratethys.

After the isolation, the Paratethys ocean became brackish. Sea life adapted to this. These adaptations still survive in the Caspian Sea. During the pliocene the Aral Sea became a gulf attached to Caspian Sea, which at times would completely dry out. In the early holocene, its connection to the Caspian was severed and it became reliant on rivers for its waters. But its fauna still dated to that time when it was a Caspian Gulf, and from there to the era of the Paratethys.

Tethys, daughter of Gaia and wife of Oceanus, was the goddess mother of the water nymphs of the lakes and the seas. Asia too was one of her daughters. The Aral Sea, this temperamental child-sea, is her offspring.

The Tethys ocean has left us much of the geology of the modern world. Its rocks and mountains are everywhere. But here is another memory. The Aral Sea is part of a line in the sand saying ‘I was here’. It is tectonic graffiti. Long might it have lasted.

Albert, September 2024

A few references

The Aral Sea Environment, 2010, Editors: Andrey Kostianoy and Aleksey N. Kosarev. Published by Springer

Paleogeographical History of the Aral Sea. Alexander Svitoch. In: The Aral Sea Environment.

The Aral Sea: A Story of Devastation and Partial Recovery of a Large Lake. Philip Micklin et al., 2020 https://link.springer.com/chapter/10.1007/978-3-030-42254-7_4

Past, Present and Future of the Aral Sea -A Review of its Fauna and Flora before and during the Regression Crisis. Igor Plotnikov et al, 2023, Zoological Studies 62, e19

The last Caspian Tiger. Robert Chandler, 2005. https://journals.sagepub.com/doi/pdf/10.1080/03064220512331339571

https://daviscenter.fas.harvard.edu/insights/aralsk-kazakh-town-lived-through-smallpox-epidemic

Banksy

264 thoughts on “The Aral Sea

    • WOW the tremor is very strong, the S2 cam isnt updated yet but when it does we might have a real show 🙂


    • (PAUD; 12-hour live; near Pauahi Crater)

      Tremor is getting stronger on this one, too. Magma is very on the move.

      • S2 updated, it is indeed a fissure further back (more west) from the spot that was making the cascade. How far back isnt really clear though yet but it is enough to not flow east into Napau. Im wondering if it might have just opened a whole new fissure at the west end and joined them all up.

        The lava flow now though seems to be going south from the vents. Depending on exactly where it is, it will either divert east and into Napau near the left side of S2 or it will just go south down the side of the volcano. It is pretty flat but it gets progressively steeper, and is very steep at the Holei pali. So this flow could flow a pretty long way if it is fed for long enough. The last cascade was kept up for nearly 12 hours.

        • I wonder what this will become. Like you said, this could look like a long one, but how long is the bigger question. If it ends within a few days, we’ll, it might just be one of those fissures on East Rift. If it lasts longer (and therefore more lava), it might produce a small shield and maybe even fill the Napau Crater to the point lava overflows to the south. I will be more surprised if this becomes a Maunaulu scenario…

          • I don’t expect that eruptions on this area last for months. The usual locations for longterm eruptions are the Mauna Ulu and the Pu’u O’o area (and satellite craters). Eruptions in Napau area are rather short or medium term events. Days to weeks. The eruption will likely be over before one month has passed.

            1997 the Napau eruption (side event of Pu’u O’o eruption) lasted for 18 days (30th January to 17th February). https://www.soest.hawaii.edu/GG/HCV/ep54.html

    • I wonder if that is an actual vebt this time, the last cascade was a direct downhill but this one is to the left. Also what that glowing spot at the far left is, my assumption is that ut is a fire but it is very bright if true.


  1. PWcam
    There are lava cascades on the SW rim of Napau…

  2. Raso Islet (Ilheu Raso) in the Cape Verde Islands seems to show thermal activity according to NASA Firms today, Sept 19th. See . It is a small volcanic island, noted for the endangered species of the Raso Lark. (45 pairs?)

  3. There are some up close videos of the eruption by Ikaika Marzo, on his facebook.

  4. The Napau eruption has a rate close to Fagradalsfjall’s size: “lava is erupting at roughly 5-15 cubic meters per second”. Maybe it will last as long as last Fagradalsfjall eruption 2023 (around 4 weeks)?
    The eruption has covered two thirds of the Napau crater floor (500,000 square meters or about 125 acres). I believe it’s easy for the eruption to cover the whole crater floor in near future.
    https://www.usgs.gov/volcanoes/kilauea/volcano-updates

    • I wonder if that is an average, the flow rate seemed a lot more in some videos.

    • Ok they are going on an average, most of the eruption has been in the last day by volume, so it might be 2-3x more than that right now.

  5. It looks like there is a lava fountain within Napau at the bottom of the cliff now, while the cascade still continues. It did look like there was a weak vent at the bottom of the cliff next to the cascade in the USGS photos but now it seems the vent is much more substantial

    • Actually, on the HVO photos, there is a strong bluish cloud coming from near the bottom of the cascade, and a cloud like this only really forms over an active vent so it seems there was something there even before.

  6. It looks like a new fissure has opened within Napau while the cascade is now weakly active. I think S2 is actually a bit further south than I thought, it might be on one of the 2011 cones, or 1997. The fissure of 1968 and 1965 is visible in front of the glow, and the earlier fissure in Napau seemed to be exactly in line with that.

    Im sure this will age poorly now I make this statement 🙂 but I think we might have just watched the birth of the successor to Pu’u O’o. SDH is still going down. UWE has flatlined, so Halemaumau seems not a primary source of this eruption, so it is plumbed in directly to the major magma chamber. If each microradian at UWE represents about 1 million m3 of magma input or output, then 40 million m3 has been lost from Halemaumau alone. I found no way to compare tilt at SDH to a volume but it is clear a significant amount of magma has been removed from there too. My guess is about 40-50 million total is a very reasonable amount and a likely underestimate. Obviously, not that much has erupted, so the majority is going into the ERZ storage and filling it at high rate but even still with enough force to erupt too.

    • This photo shows the lava path from the fountain to Napau Crater:

      https://www.bigislandvideonews.com/2024/09/19/kilauea-eruption-update-for-thursday-september-19/

      The lava has covered estimated 80% of the Napau Crater floor: https://www.usgs.gov/media/images/september-19-2024-thermal-map-eruption-kilauea-east-rift-zone

      The present fissure line is in the line of the early Napau fissure eruptions 1968. They were more towards NW than the later side-events in Napau area during Pu’u O’o era.

    • It might be a bit too soon to know if this is the successor to Pu’u’o’o. Normal fissure eruptions in this area have lasted up to 15 days (Oct 1968),

      • Yes that is probably true but in tbe small chance we are still watching this in 2055 I can say I called it within the first week 🙂

        It also should be noted to that, but while October 1968 didnt evolve into a shield directly, it was only a few months before Mauna Ulu. And Pu’u O’o was very close to being on the same line. So is this eruption now actually… I dont think it will take a decade of rifting to evolve into something longer anyway, the 1960s was the ERZ waking up after being mostly inactive for a century before. Where now it is only a couple years gap, barely 6 years after the last eruption ended, and magma has been flowing through it at high to extreme rate for most of the last 40 years pretty continuously otherwise. Its a very well worn path now.
        If the volcano had continued to intrude the SWRZ I think we would have seen something more like the 1960s, which is why I was so sure of it erupting there again after June, but Pele had other plans. At least we got to see a SWRZ eruption, it might be another 50 years to the next one…

        • October 1968 happened after seven years of MERZ activity (starting 1961 with a 21km long fissure eruption from Napau). Now we see the first MERZ eruption since 2018. The Napau Crater is very shallow, it has been filled up with lot lava pre-historically. Maybe there were eruptions that were more voluminous than during 19th and 20th century.

          A question is, when did the Napau Crater form and how deep was it originally? Most craters there are not created by eruptions, but by deep cracks that migrate upwards (like a sinkhole in limestone). https://www.nps.gov/havo/learn/nature/pit-craters.htm
          ?maxwidth=1300&autorotate=false&quality=78&format=webp

          • Not all pit craters are created equal. One formed in 1955 almost on Highway 130, and it was glowing, and old lava melted into stalagtites. Then there’s the Outlook vent, and also the countless ones that formed at Mauna Ulu.

          • That’s the Devil’s Pit model, which probably formed as some sort of collapsed tube, it does not work well with the big pit craters (Keanakakoi, Luamanu, Puhimau, Hiiaka, Pauahi, Alo, Alae, Makaopuhi, and Napau) which have not shown any growth historically despite some of them being younger than 18th century lavas. Probably the 1790 collapse made a few of them by draining down ERZ storages.

            The only thing that’s certain about Napau’s age is that it predates 18th century ERZ eruptions, given that it has a fill of prehistoric lavas, and that it postdates the ~1100-1200 AD shield of Kane Nui O Hamo which would have likely buried Napau entirely, given that it was a Pu’u’o’o scale eruption. Likely Napau is of similar age to the East Makaopuhi crater, both being the largest craters of the ERZ, about one km wide and likely very deep originally. Probably formed in some deep collapse, maybe the one that was associated to the Upper Kulanaokuaiki explosive eruptions shortly after Hawaiians arrival to the island around 1100 AD (collected in the old myth-like Kamapua’a-Pele fight story).

      • I’d exclude a 35 year long Pu’u O’o eruption for near future. 1983 happened after 20 years of very heterogenous eruptions from SWRZ over Halema’uma’u to MERZ. The 18th century showed, that the larger Pu’u O’o area is the dominant actor on MERZ, but it can also do minor events.

        I think it’s probable that next eruption will happen down- or uprift of the present location. Either in the Mauna Ulu or the Pu’u O’o territory. But as monogenetic vents. We also can’t exclude a return of magma to Halema’uma’u as it happened 1967-1968 (251 days, 0.09km³ volume).


  7. (UWE; 2 day; live)
    Seems the tilt has begun uplift again, but may or may not last long.

    • The Pu’u O’o tilt is still confusing for me. The green line goes up, the blue line goes down, but both are flattening:

      ?fileTS=1726842351

      • The tilt number is in degrees, presumably around a circle that has 0 being north. So the blue line is recording tilt coming from the southwest, while the green line is recording from the northeast. Roughly anyway.

        So basically, Pu’u O’o moved east very fast, then back west after the eruption started and the ground stabilized.

    • Tremor is now strengthening on summit and upper-mid East Rift seismographs, especially on the PAUD one…

        • Is this significant tremor (Pu’u O’o station)? How would new magma interact with the old 1983-2018 volcano shield?

          ?fileTS=1726843629

          • Maybe the magma would add to the body for future eruptions, keeping it from being stale, but doesn’t mean it’ll somehow reactivate Pu’u’o’o. Instead, it might just stay, accumulating magma there until the next eruption unfolds…

            Speaking of which, I still think Napau is going to be next site of a new shield, at least similar to that of Maunaulu, just maybe or maybe not with this eruption. Besides, it is in area of shields, although short-lived fissures are more frequent. There might have to be more shorter eruptions in the area to signal the coming formation of something like that. Only time would tell.

          • And looks like the tremor is only temporary. Spoke a little too soon.

          • The map of 18th century that Chad published repeatedly, shows that the centers of lava activity were the Mauna Ulu and Pu’u O’o area like 1961-2018. So these are the main actors on MERZ. Pu’u O’o is the “king”, Mauna Ulu is the “vice king”. Napau is between the dominant actors, but was often more leaning towards Pu’u O’o …. like independent voters in the USA that lean towards a party.

            Maybe we get some kind of monogenetic eruption in the Pu’u O’o area that behaves different to the 1983-2018 Pu’u O’o eruption. The present Napau eruption may be the precursor for something bigger.

          • Maunaulu and Pu’u’ō’ō are indeed the most well known ones, but not really the only shields here. There is also Kānenuiohamo (formed before Makaopuni Crater formed) and “that unknown shield south of current fissures”, and maybe no doubt countless more buried under more recent lavas. I do think that, if this eruption goes into shield forming mode, it’ll either take magma from the Maunaulu magma body or maybe form a new magma body, the latter of which will take a long time.

            Maunaulu and Pu’u’ō’ō are really only “monogenetic” shields (quotations because there is a chance fissures will cut across their summits and/or bury them) and only special because they’re the only ones we’ve ever documented extensively. There could’ve been larger ones that might’ve erupted for vastly longer timescales in the past. Maybe even Kānenuiohamo was larger than Maunaulu, just its lavas are either buried or destroyed. It might be possible it may, like you said, closer to a certain shield because of the bodies, but it could also go on its own area, we just don’t know it yet.

          • The ERZ between Mauna Ulu and Heiheiahulu is a magma storage area. If the supply is high there isnt really anywhere that is more preferred, its just a factor of supply rate vs gravity vs distance from the summit source.

            In the 20th century Halemaumau was high up, over 1 km elevation after 1968. Mauna ulu started at 950 meters elevation, grew about 100 meters, and then twice it failed and diverted to eruptions at the summit or higher up on both rifts. Even then the summit didnt deflate until the SWRZ eruption of 1974, in a way that is the true end of Mauna Ulu. But the key point is that the eruption only stopped because Mauna Ulu got to the same height as Halemaumau, and not because the area it formed was not as important. Pu’u O’o in 2018 reached a vent height of about 870 meters elevation and the summit lake about 150 meters higher but over 20 km distance that is pretty flat.
            There is also the 1975 earthquake that opened the ERZ significantly, over 5 meters in places. And there was also a quake in 1989, 6.1, which didnt do anything immediately but maybe added to the above a bit.

            Now, not only does the above factor still apply, but another earthquake of similar size and displacement occurred, and a major increase possibly even doubling of magma supply rate in the interval. The fact that as soon as Halemaumau got to about 1 km elevation again magma began filling the SWRZ and south caldera storage extremely rapidly, recovering all of the local 2018 drop in a year, and then going to the ERZ and now erupting there only a year after the last eruption in Halemaumau…
            Back in 2018, in the absense of any other data, HVO said it would take 10 years of Pu’u O’o supply to recover, and that was before revised significant increases in the eruption volume. Well, we are looking at an eruption near Pu’u O’o in 2024 not 2028 🙂

            It seems to have stopped now, but that is the first test, will the summit reinflate and reactivate this vent in a few weeks. The fact the magma was mostly going into the middle ERZ storage anyway before this, might skew the results a bit…

    • Only at Halemaumau, SDH is still falling, so there is still magma flowing to the area. But having Halemaumau inflating is an interesting twist.

      This also is pretty similar to the early days of Pu’u O’o… Deflation then inflation, which became consistent and episodic after a while. The fissure is still glowing in the night view, and the Halemaumau tilt has started acting up, so maybe the next phase is about to begin. It might be further up the hill, at the west end of the fissure system, maybe sending a flow down the south flank. Or it erupts in Napau again. I think we might find out in a day or two.

      • POC tiltmeter deformation is consistent with Napau inflation, so maybe that’s where the SWRZ magma is going.

        • I think that is probably correct. The magma hasn’t yet opened pathways further downrift. The tilt meters are sensitive to changes that may have happened a long way off.

          • Yes Pu’u O’o would have been moved way more if a dike went under it, or past it. The GPS are all offline maybe being fixed on the site, but HVO said one of the stations near Makaopuhi moved 50 cm, and all of the stations near the intrusion moved at least 20. I forget which direction.

            I tried to make a map of the eruption, i cluding the intrusion, but having the dike be one unit starting near Mauna Ulu doesnt really work to get an eruption at this location. I think maybe there were two dikes, one that failed and happened in the Alae (Mauna Ulu) fissure swarm, and another that erupted from the magma chamber of Makaopuhi and Napau. The earthquakes stopped a bit east of the edge of Napau, a bit past the easternmost vents, so not to Pu’u O’o.

            If that magma chamber is the source and is still inflating there will probably be more eruptions, maybe suddenly if there is an open path now.


  8. This is Napau Crater and it is covered in a lot of lava.

  9. Report on GVP about Kilauea in January 1983, and the start of Pu’u O’o.

    https://volcano.si.edu/showreport.cfm?doi=10.5479/si.GVP.SEAN198301-332010

    The eruption was bigger than the new one, but that isnt too surprising as it was lower down, Halemaumau was a lot higher, and the amount of deflation was about 3x as much. The sequence was in a lot of ways otherwise very similar. The eruptions in the 1960s, in the same area, were mostly not like this and I dont think any of them started tiny and got stronger later on.

    https://volcano.si.edu/showreport.cfm?doi=10.5479/si.GVP.SEAN198302-332010

    From February 1983, the next significant episode after a gap of mostly nothing. In the gap was constant low level harmonic tremor and persistant incandescence and degassing at some of the fissure, where it erupted again.

    It is noted that reinflation of the summit wasnt major between events, and was usually (always?) exceeded by deflation of the subsequent episode. I think Pu’u O’o was draining the summit until 2007 when supply increased, and the summit vent formed within a year… But early on, the initial reinflaation was very fast up to 1 microrad a day which is what we see right now.

    • The eruption is doing a pause, but it’s uncertain whether it’s the end of the eruption, whether it will continue or whether it’s the end of an episode.

      • In sum the eruption began on September 15th and paused on September 20th. If the eruption is finally over, it was a five days eruption.

        The last volcanic activity on Napau before this eruption was 2011:
        “On March 5, 2011, following rapid summit deflation and increased seismicity, the crater floor of Pu’u ‘O’o collapsed. Within a few hours, it had dropped 380 feet (115 meters). Shortly thereafter, lava broke to the surface between Pu’u ‘O’o and Napau Crater, marking the start of the Kamoamoa fissure eruption, which was active through March 9.”

    • Zach:
      I don’t think that this is the end. I think this is phase 1. The last eruption series had a breakout of a fissure eruption that went from vent #1 to vent #23, before it finally settled down to vent #8. Look for something new to pop-up further eastward along the rift zone.

      • Not further east, the earthquakes stopped pretty much exactly where the east side of Napau is, and Pu’u O’o didnt move consistent with a dike opening under or next to it. I do think a future eruption will be basically in the same place and could extend further east, but a silent reactivation would be within the existing length.

        Theres probably a lot more variables, and not being able to see the GPS is a bit frustrating if necessary to fix them. But the rate Halemaumau is inflating now, 1 microrad a day, it will be back up to pre eruption in about a month. SDH is still showing magma draining from the major chamber to the ERZ though.

  10. Today Krysuvik had an earthquake (M2.9, 5.6km deep) close to Kleifarvatn’s shore. How to tectonic movements there influence the paths of magma? It is the next system east of Fagradalsfjall. Can magma enter there?

  11. There is still incandescence on the fissure above Napau crater, it is weaker than a day ago but it is also bad weather too which might be making it look dimmer than it actually is. There seems to still be some amount of tremor near the eruption too.

    • I have noticed too that there are a lot of yellow depth quakes under Kilaueas summit following the eruption, at about 5-10 km deep. Usually quakes this deep are on the south flank, but this is probably the bottom of the major magma chamber too,

      I guess, maybe this is extra magma rising up because of decompression. That could actually be why the tilt at SDH isnt going down as fast, extra input not slower output. Without the GPS though its not really possible to tell.

      • Maybe the summit first needs to do some kind of inflation, before during next deflation the next intrusion or eruption on MERZ is going to happen.

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