Sakurajima eruption

[bjdeming]

Nah, it's coming from that area -- I watched it re-form. Haven't seen fumaroles on the cam there before, but it does look like hot air is rising from various scattered points, with subsequent condensation of water vapor.

There's no oomph to it, though the appearance of convection is worrisome (if it wasn't a mistaken glimpse of the plume from the crater on the other side of that rock wall).

They just issued a routine report yesterday! (It's Tuesday there now.)

Well, they have Sakurajima wired in every possible way -- they've even tunneled into it to place instruments. No one is warning of an eruption or other trouble yet. We'll just have to see what happens next -- wish there was a public-facing thermal cam.

 

[bjdeming]

Its intensity seems to pulse up and down slowly and now seems on the wane. It could be some quirk of water circulation inside the mountain, combined perhaps with erosion.

That recent slow-moving Typhoon No. 10 made landfall nearby and the volcano's summit was wrapped in wind-driven clouds on cam for at least a couple of days.

 

[bjdeming]

That area apparently dried out, as the summit flank has been back to its normal appearance on cam from the following day on.

I did not see mention of it in the observatory's update through the 11th.

Sakurajima is having the occasional typical (though, again, more intense) vulcanian blast:



It does look quite apocalyptical on cam just now --

-- but that seems to be storm clouds, and 2 a.m. lighting, as far as I can tell.

 

[bjdeming]

No major changes -- still Level 3 and still doing more intense and ashier explosions than during its "soccer-game" period -- but Zaiho has a nice video of the 12/27 blast that also shows split-level meteorological cloud movements and just some darn pretty backscattering in the background as sunset approaches. (Camera D is a new feed and located somewhere on the north bay shore, perhaps Kirishima; the other three cams are in Kagoshima City.)



Today's update via Google Translate includes that eruption:

16:00, December 27, 2024 Fukuoka Regional Meteorological Observatory and Kagoshima Regional Meteorological Observatory

＜Warning around the crater (volcanic alert level 3, mountain entry restrictions) continues＞
　We would like to inform you of the activity status of Sakurajima from December 23rd to 15:00 on the 27th. There is a risk of an eruption accompanied by large volcanic blocks and small pyroclastic flows scattering more than 1 km from the Minami-dake summit crater and Showa crater.

Volcanic activity status​

　Active volcanic activity continues at Sakurajima.
　
　Two eruptions occurred at Minami-dake summit crater, both of which were explosions. In the explosion that occurred at 07:29 on the 23rd, smoke rose up to 3,400m above the crater rim, and large volcanic rocks scattered in a ballistic trajectory reached the 7th station (about 1,000m from Minami-dake summit crater). In addition, fire reflections were observed at the crater throughout the period at night using a high-sensitivity surveillance camera.
　
　No eruptions or fire reflections have been observed at Showa crater.
　
　Volcanic earthquakes have been few. No volcanic tremors have been observed.
　
　In a field survey conducted on the 24th, the amount of volcanic gas (sulfur dioxide) emitted was high at 2,000 tons per day (3,400 tons on the 17th).
　
　In a field survey conducted on the 25th, no particular changes were observed in the geothermal conditions on the southeast slope of Minami-dake or near Showa crater compared to previous observations. In addition, within Sakurajima, a glow from the Minami-dake summit crater was observed, barely visible to the naked eye.
　
　Continuous GNSS observations have confirmed slight shrinkage on the baseline within Sakurajima since around January 2024, which is thought to be due to mountain shrinkage. In addition, the baseline that sandwiches the Aira Caldera (inner Kagoshima Bay) has shown a gradual expansion indicating a long-term expansion deep underground in the Aira Caldera.
　
　In Sakurajima, magma has been accumulating deep underground in the Aira Caldera (inner Kagoshima Bay) for a long time, and the amount of volcanic gas (sulfur dioxide) emitted is generally high, so it is thought that eruptive activity will continue in the future. Please pay attention to future volcanic information...

Of note, and not to be sensational -- just to put Sakurajima in perspective -- Aira has had a supereruption in the distant past, so it's a supervolcano but nothing along those lines is looming in the near future and likely not during our lifetimes.

It's just doing what all restless calderas do and venting through Sakurajima on the south caldera rim now.

Sakurajima, as mentioned, is the real threat since it goes plinian every now and then, last in 1914.

 

[bjdeming]

Sakurajima flexed its muscles a little, roughly 24 hours ago:



Just a little. They didn't raise the alert level or issue a special statement on just one vulcanian event.

Things get bad when it's in the mood, which last happened in 1914 (PDF download of research paper).

Per JMA updates through the 17th, the volcano has been more explosive in terms of frequency, but not intensity, and instruments still measure shrinkage (while its daddy, Aira Caldera, continues with the long-term slow inflation).

 

[bjdeming]

This is getting to be a habit with Sakurajima but today's three-day update from JMA includes this explosion and the alert level is unchanged:



Just to review: Aira's expansion is where it was before the 1914 big Sakurajima eruption, which has everyone watching closely. What we don't want to see are flank fissures opening a la 1914.

 

[bjdeming]

NHK just did a story noting that Sakurajima has had 50 eruptions so far this year -- more than in all of 2024.

JMA's update reported 9 eruptions between March 31 and April 4, four of them explosive. They left the alert at Level 3.

And then, this today:



Tokyo VAAC reported ash up to 13,000 feet. It wasn't sustained, though, and JMA has not updated their page, at least not yet. Level 3 is still in effect, per that.

Again, the ground above Aira Caldera, on whose rim Sakurajima sits and from which it gets its magma, is at the same level it was just before the 1914 Taisho plinian eruption.

If Sakurajima were to blow now, I don't know if the summit would be the vent or if a set of fissures would open up on the east and west flanks, as in 1914.

At least the people are aware and they do drills and have a robust plan. Hope it's never needed.

 

[bjdeming]

Zaiho hasn't yet posted video of the April 5 blast but here is one on April 2 (when, I'm guessing, a dome blew up).

The larger ballistics, still incandescent, show up nicely in the twilight. This is one reason why there are exclusion zones on active volcanoes.

 

[bjdeming]

(From the blog just now)

Per today’s JMA update, Sakurajima had 12 eruptions, eight of which were explosions. Level 3 alert is maintained.

While this is all still relatively low intensity, it is a change in behavior from those long-gone days of vulcanian blasts now and then.

If those could be compared to a hand slapping a volleyball, this layperson sees it now as a clenching fist, with arm muscles tightening for a blow.

This explosion below, some ten hours ago, will count on the next update. Note that the plume, while impressive, does not have the power yet to completely ignore prevailing winds and rise vertically.

Yet.

 

[bjdeming]

X translation: "Sakurajima today" -- actually yesterday, given the time zones. Still, when it's quiet, it's beautiful.



BTW, that edifice is the result of two volcanoes that formed and then combined, their respective craters both being active for a while, although now it's just North Crater, Minami-dake, that's active.

A third, smaller crater, Showa, opened near Minamidake in the twentieth century and has had some lava flows and other activity but it has been quiet recently.