Sakurajima eruption

[bjdeming]

The weather clouds have kept it obscured all day but it seems that the volcano is still fuming.

JMA's report today via GT:

Kagoshima Regional Meteorological Observatory announcement

＜Warning around the crater (eruption warning level 3, mountain entry restrictions) continues＞

At Sakurajima, the mountain body is in a state of expansion. There is a risk of an eruption accompanied by large volcanic rocks and small pyroclastic flows that will fly over 1 km from the Minami-dake summit crater and Showa crater. Also, be careful of ashfall on the downwind side.

Current volcanic activity

At Sakurajima, the mountain expansion that had been continuing since around 20:00 on the 12th, was temporarily contracted due to eruptions from around 11:30 to 15:30 on the 15th, but has started to expand again.At the Minami-dake summit crater, 12 eruptions and 11 explosions occurred between yesterday (16th) and 15:00 today (17th), and the smoke rose up to 2,700 m above the crater rim. Large volcanic rocks were scattered in a ballistic trajectory and reached as far as the 6th station (about 900 m from the Minami-dake summit crater).No eruptions have been observed at the Showa crater.

The areas around both craters have been covered in clouds since 8 p.m. yesterday, and the status of the smoke is unknown. There is a possibility of further eruptions accompanied by large amounts of ashfall, mainly on Sakurajima Island. Please use the ashfall forecast issued by the Japan Meteorological Agency to determine the areas where ashfall and small volcanic rocks are expected to fall.

Disaster prevention precautions, etc.

Within approximately 2 km of the Minami-dake summit crater and Showa crater, be on the lookout for large volcanic rocks and pyroclastic flows that will be scattered in a ballistic trajectory due to the eruption.

On the downwind side, be careful as not only volcanic ash but also small volcanic rocks will be carried by the wind and fall far away.Be careful as there is a risk of window glass breaking due to large air vibrations caused by the explosion.

Please also be aware that depending on the future ashfall situation, there is a possibility of mudslides occurring during rainfall.

There have been media stories that mdntion loud noises and "air vibrations" but no reports yet of broken windows. People walk around with umbrellas and masks and of course it has played havoc with local air yraffic.

 

[bjdeming]

Hazards at all volcanoes sometimes walk on two legs and feel good, being accustomed to their restless volcano (which is the problem). These tweets by a local academic who lectures about Sakurajima reminded me of that -- and also of how wonderfully it must concentrate the mind to be on an island with that volcano and with no broad highway available for emergency escape (? if there's a road over the lava causeway).

To counteract this at Sakurajima, it's helpful that they do drills and other things every January 12, the Taisho anniversary. There's other public outreach, too. But how to bring the reality of a possible major eruption home before it actually happens...?

(BTW, Tokyo VAAC reports that Sakurajima went off again about an hour ago, but the ash is low, around 7,000 feet.)

 

[bjdeming]

No major changes one way or the other. On the one hand, it's back to vulcanian activity (explosions and brief eruptions); on the other, the frequency and intensity level of this activity are much higher.

This is all per report and ashfall forrcast graphic -- the mountain is still cloud-wrapped on cams.

From todays update (the 19th; it's already the 20th over there), via GT (emphasis added):

...There were 86 eruptions and 44 explosions at the Minami-dake summit crater. The explosion that occurred at 18:54 on the 18th sent smoke rising 3,200 m above the crater rim. Large volcanic rocks, which were scattered in a ballistic trajectory, reached as far as the 5th station (approximately 1,200 m from the Minami-dake summit crater).

No eruptions have been observed at Showa Crater.

Volcanic earthquakes have been occurring at a somewhat high rate. Volcanic tremors have occurred, mainly associated with eruptions...

Level 3 volcanic alert, still. Wonder how human alertness and caution are holding up locally. Increased volcanic activity can really wear you down before things peak (which, hopefully, Sakurajima has already done).

 

[bjdeming]

PS: Also, latest Tokyo VAAC advisory puts the latest eruption at about an hour ago, with ash to 10,000 feet.

 

[bjdeming]

Just a cool visual on (I think) the local situation. Dr. Imura, per X, writes "Drive with caution" -- can't read the sign but a comment mentions ashfall, which isn't evident here at the moment:




Just for reference, all the guides do say that ash makes roads slippery, especially if it's wet; also, it can mess up engines and electronics.

And, of course, especially if this is on the island, other things besides ash can come down when a volcano is erupting, and a particularly voluminous emission can turn day into night really fast.

 

[bjdeming]

Way fewer eruptions reported in today's update, as well as by Tokyo VAAC, and an astonishing jump to five-digit sulfur dioxide emission (TROPOMI satellite picked it up, too). This layperson wonders if the "plug" -- supposing one existed -- has disappeared. Hope so. They say the mountain is still expanding, though.

Via GT:

...Minami-dake summit crater, 19 eruptions occurred from yesterday (20th) to today (21st) at 3pm, 13 of which were explosions. The smoke rose up to 3000m above the crater rim. Large volcanic rocks scattered in a ballistic trajectory reached up to the 5th station (about 1200m from Minami-dake summit crater).

No eruptions have been observed at Showa crater.

In a field survey conducted yesterday, the amount of volcanic gas (sulfur dioxide) emitted was very high at 11200 tons per day (300 tons last time on the 12th)...

C'mon, settle down, Cherry Blossom!

 

[bjdeming]

It's not settling down, with multiple eruptions noted by Tokyo VAAC (most recently about 1-1/2 hours ago). Here's a news story (Japanese) on one. The tilted plume is now a weird-looking thing across the whole bay.

Dr. Imura got an excellent photo of the present cloud's early stages and wrote, per X translation, "According to the Japan Meteorological Agency's "Kagoshima Volcano Eruption Criteria," it may not be classified as an "eruption," but since colored volcanic smoke containing ash is emanating from the crater, volcanologically speaking, it can be said to be erupting."



That is continuous, not vulcanian.

Barring major changes, today's update should be out in six to eight hours.

 

[bjdeming]

Re: the sailing ship, he just added, via X translation, "The "Nippon Maru" has been in Kagoshima (since about three days ago)."

 

[bjdeming]

Zaiho posted video of this morning's eruption, which occurred almost five hours ago now. The volcano is still having low-level ash emission, but at least is now well visible -- the skies have cleared quite a bit.



Sigh.

Here's an interview with a Sakurajima expert from 2014.

PS: Cam D is obviously not in Kagoshima -- judging by angles, that urban area is probably a part of Kirishima, or somewhere near that city on the north bay shore. It has volcanic connections, too, but these are behind us as we look through that cam.



And Aira caldera bubbles away under the water in between the north/northeastern shore and Sakurajima.

Kagoshima -- the Graben of Fire.

 

[bjdeming]

I've been looking up precursors to the VEI 4 Taisho eruption, to see how they compare to current activity, and apparently there wasn't eruptive/explosive activity, as there is today.

As this figure from a 2025 paper by Dr. Iguchi (the expert interviewed at that link in a previous post) shows, there were other precursors: LOTS of earthquakes, changes in tidal levels, wells emptying out:

That's CC BY-NC-ND 4.0, and here's the caption: "Fig. 2. Phenomena related to intrusion of magma to Sakurajima Volcano. (a) Magma plumbing system from Aira Caldera to Sakurajima Volcano. A: Main reservoir below Aira Caldera, K: Pressure source below Kitadake [6], M: Minamidake, Orange rectangle: inferred dyke intrusion leading to a flank eruption. The strike direction of the dyke is not specified. (b) Abnormal phenomena one day before the Taisho eruption. Upper is hourly number of earthquakes and lower is tide change. Some abnormal phenomena are inserted in the figure. (c) Precursory process to the Taisho eruption."​

(Kitadake is the other summit crater and has not been active for quite a while.)

Those phenomena are just what people noticed. Today's monitoring would pick up much more (and it hasn't yet). Apparently plumes didn't appear until just before the blast <layperson speculation> which might mean that Sakurajima's activity now, while worrisome with a recharged magma reservoir present, might actually be a good thing -- letting off steam, so to speak, rather than keeping it penned in to build up to plinian levels. </layperson speculation>

Nervewracking for everyone around it, though.

Dr. Iguchi's downloadable paper at that link is very good but he does not mention the great tragedy of that January day in 1914.

I wrote it out as an epilogue in the Decade Volcano book and might already have mentioned it somewhere at TalkWeather, but here it is again along with a link to information about the most famous local memorial (scroll down).

Basically, the meteorologists/volcanologists screwed up and people died.

Epilogue:

To err is human, but forgiveness takes time when a volcano is involved.

A tragedy — and a forecaster’s nightmare — played out at Sakurajima in 1914. It is worth mentioning in a book about Decade Volcanoes to underscore the reason why experts in many fields work so hard to get things right and try not to take anything for granted.

There are “monuments to distrust of science” here.

I have only found mention of this online in the Japanese Wikipedia, which is the source (Japanese) of quotes below (via Google Translate).

As we’ve seen, Sakurajima was one of the first volcanoes to be monitored with modern techniques. In the early twentieth century, as now, public warnings and other volcano information came from official weather offices.

On January 11, 1914, a small landslide occurred near Sakurajima’s summit and “thin white smoke rose on the mountainside.”

The next day, from 8 to 10 a.m., “a mushroom cloud-like white smoke was seen boiling from the middle of Sakurajima.”

The local weather office reportedly said this cloud was a meteorological phenomenon. Civic leaders on the western side of the volcano believed them, staying put while others fled the scene.

Unfortunately for those who stayed behind, that cloud was actually an early sign of the Taisho eruption.

At about 10 a.m., a new fissure opened up on Sakajurima’s western flank with a big explosion. This was followed about ten minutes later by a similar blast from a twin fissure on the eastern flank. The two vents quickly escalated to Plinian-style levels of activity.

Pumice poured down onto the bay, limiting the movement of rescue ships. Sakurajima’s remaining residents, in the translated words of Japanese Wikimedia contributors, “rushed immediately after the eruption started on January 12 and it became a big mess . . . in Higashi-Sakurajima village, there were a number of people who fell off the coast due to confusion and people who froze to death or drowned in an attempt to swim across to the other side [a 2.5-mile swim across open water. In January].”

There can be no blame for the mistaken interpretation of that white cloud early on the morning of the 12th. The experts made their best call, based on what little they knew.

Science always walks the fence between objectivity and common sense. And scientists are only human, while volcanoes have many ways to surprise us.

The civic leaders weren’t wrong, either, since they followed official information.

Nevertheless, the mayor of Higashi-Sakurajima felt so bad about the loss of life that he wanted to put up a memorial to warn future generations.

He couldn’t manage it, but his successor did, erecting the monument on the tenth anniversary of the eruption’s start.

Even without that, no one will ever forget the 1914-1915 eruption of Sakurajima. Today they conduct evacuation drills on that day, January 12th.

 

[bjdeming]

With good weather, Dr. Imura took some time lapses of Sakurajima's recent vulcanian (yay!) bursts from the roof of his lab building (apparently that's in the Kirishima area somewhere):

 

[bjdeming]

No major changes, other than a return (per Tokyo VAAC advisories) to vulcanian explosions after a lengthy period of low-level continuous ash emission.

Alert is still at Level 3, and per today's update (via GT):

...A field survey conducted yesterday (22nd) found that the amount of volcanic gas (sulfur dioxide) emitted was very high at 4,300 tons per day (11,200 tons on the 20th). Observations using tiltmeters and extensometers installed on the island indicate that the mountain continues to expand...

Expanding while in eruption cycles. Sigh.

 

[bjdeming]

Per Tokyo VAAC advisories, several hours ago Sakurajima had three explosions in fairly close succession, with ash reported from 7,000 to 17,000 feet (nothing that would raise the alert level, but a high frequency).

Per browser translation of this article (Japanese):

Explosive eruption at Sakurajima, smoke rising to over 3,500m [Today and tomorrow ashfall forecast] Ashfall expected up to Kumamoto and Oita prefectures Kagoshima (23rd, 8pm)​

Minami Nippon BroadcastingFriday, May 23, 2025 20:22

That's the island of Kyushu. (When it really gets going, Sakurajima is capable of ashing Tokyo, on the next big island to the north.)

The news story goes on to list the many places on Kyushu expected to receive ashfall.

Also, Dr. Imura just tweeted that Showa crater was steaming. As noted in the updates, Showa has been quiet throughout this recent uptick in activity (and for quite some time before it, too).

? if significant, but it's still a change.

 

[bjdeming]

There are no more advisories up at Tokyo VAAC right now; I kind of wish there were -- a quiet volcano can still be quite active out of sight.

Sakurajima is cloud-wrapped on the cams but that hasn't hindered advisory issuance before.

JMA's ash forecast website shows a cloud (red hash-mark) near the summit.

Per this story (Japanese) from a local TV station early on the 23rd local time (so, on the 22nd in US time zones), some crop damage is reported -- the area is a famous agricultural region -- and people are advised to wear long sleeves despite the warm weather.

Also, an expert is quoted saying that this could go on for a while and also that no one is certain about what will happen next.

In terms of worst-case scenarios, which this hasn't turned into yet and hopefully never will, a volcano's history is merely a guide for experts, not a template they can use for forecasting.

Sakurajima has had other plinian-style episodes besides the one in 1914, including one in the 1700s and one in the 1400s. Those are not as well documented as the twentieth-century Taisho event, which is too bad because a dataset of three is better than one (though still very small and limited).

In 2017, Italian volcanologists used those long-ago cataclysms plus the one in 1914 for a paper; not sure, but I think it's also used by emergency planners for worst-case planning today.

All hypothetical thus far, and may it remain so into the future!

 

[bjdeming]

A peaceful moment!

From the blog:

May 24, 2025, 4:44 p.m., Pacific: Sakurajima is doing something this morning in Japan —



— but it’s at a very low level.

JMA did not issue an update yesterday and there have been no new advisories posted at the Tokyo VAAC website since the 23rd (UTC).

This is good.

Could Sakurajima have had its climactic paroxysm for this cycle?

If so, given the volcano’s history, a lava flow is not inconceivable, but it probably would be small given the small size of those three explosions when compared to plinian-style activity.

We’ll find out more whenever JMA issues its next advisory — it might not be today, since they went at least three days in between updates before this crisis — or whenever Sakurajima gets angry again.

 

[bjdeming]

JMA had gone back to three-day updates and so (from the blog):

May 28, 2025, 5:53 p.m., Pacific: Sakurajima appeared quiet on the cams yesterday and overnight, plus there were no new Tokyo VAAC advisories on this volcano, so I didn’t check the JMA updates, not expecting another until the 29th.

The boffins snuck one in! I don’t know why, specifically, as it references just a few eruptions, as well as no explosions or notable seismicity, and the alert level is unchanged, but suspect it is because the edifice is still expanding.

This layperson understands that to be a sign that more violence — probably not plinian style, given the lack of intense precursors — may be possible in the future. The explosions on the 24th, which ashed central Kyushu, were not the final paroxysm.

Here’s the relevant update text via Google Translate:

16:00, May 28, 2025, Fukuoka Regional Meteorological Observatory and Kagoshima Regional Meteorological Observatory
This is an update on Sakurajima’s activity from May 26 to 15:00 on May 28. There is a risk of an eruption accompanied by large volcanic rocks and small pyroclastic flows scattering more than 1 km from the Minami-dake summit crater and Showa crater.
Volcanic activity status
Eruptive activity continues on Sakurajima.
Very small eruptions have occurred occasionally at the Minami-dake summit crater. No explosions have occurred since the 24th.
No eruptions have been observed at the Showa crater.
Volcanic earthquakes have been few and far between. No volcanic tremors have been observed.
Observations using tiltmeters and extensometers installed on the island indicate that the mountain continues to expand.
Continuous GNSS observations have shown gradual expansion over a long period of time along the baseline that borders the Aira Caldera (inner Kagoshima Bay), indicating deep underground expansion of the Aira Caldera.
At Sakurajima, magma has been accumulating deep underground in the Aira Caldera (inner Kagoshima Bay) for a long period of time, and the amount of volcanic gas (sulfur dioxide) emitted is also generally high, so it is thought that eruptive activity will continue in the future. Please pay attention to future volcanic information…

A quiet volcano can be a dangerous one. Frequent earthquakes were felt before the Taisho 1914 "big one," and those are not present now, per JMA updates. Still, what we don't want to see is flank fissures opening up, as happened in all three of Sakurajima's last plinian-style eruptions, presumably because pressure and magma intrusion combined to form a dike.

Sakurajima did have a dike intrusion ten years ago and nothing untoward happened. But that was before this recent change in behavior, back in the good old soccer game/vulcanian eruption days.

Now, hopefully, magma and pressure will continue to find outlet through Minamidake summit crater.

 

[bjdeming]

Scary-looking weather clouds plus a summit plume of sorts (probably steam) on Cam D!

May 29,12:08 a.m., Pacific: Two VAAC advisories up: Sakurajima erupted about half an hour ago, with ash to, first, 6,000 and then 9,000 feet. That’s not very high.

No JMA updates yet. The volcano is partly visible on cams but the weather is cloudy and raining.

Edit: The current Zaiho Cam D shot is impressive because of weather and also shows that Sakurajima is fuming:

 

[bjdeming]

This local TV article (Japanese -- sorry about the ads) has video of what I saw in the cam. They intersperse cuts of eruptions on other days, but at the end is today's eruption cloud, mixed in with weather.

It looks like a tornado wrapped in rain but there was no rotation and seen from other angles the difference between weather and volcanic cloud was obvious.

Cool video!

Of note, no more VAAC advisories have been posted, no new JMA update is up, and the volcano is just sullenly fuming a bit in twilight on the cam.

PS: Yes, it literally rained ash in Kagoshima:

 

[bjdeming]

Minamidake is still open. There were a couple of explosions on the 30th (ash up to 14,000 feet, per VAAC advisories), followed by a period of low-level continuous ash venting.

All was then quiet until a little over two hours ago when this happened (Tokyo VAAC says ash up to 15,000 feet):



On the live cam, Sakurajima is venting continuous low-level ash again.

This layperson doesn't like it -- it's too much like repeated attempts to kick-start an engine.

One possible bright spot: JMA was ambiguous about the mountain expansion in their May 30 update; also, no uptick in seismicity was noted.

We'll just have to wait and see...