Volcano thread (1 Viewer)

bjdeming

Member
Sustaining Member
Messages
721
Reaction score
469
Location
Corvallis, Oregon
It's amazing to watch, but this is what Sakurajima used to do: one-off vulcanian shots and you were fine as long as you stayed out of the summit exclusion zone.

They knew they were in no danger, and they see hundreds of those pops every year.

That changed over this past weekend, unfortunately.

See how it keeps coming this time?


The volcano has switched to continuous explosive behavior for the last three days and evacuations are underway on the peninsula and, I think, in parts of Kagoshima City.

You can't tell that from the live cam: there's an unusual number of boats in the bay currently (at sunset).



This Decade Volcano is in a complex setting that includes a large submerged caldera, and the quickest way to explain that is with this post/book chapter. Am not beating my own drum here -- it's just the easiest way to describe why this is a particularly dangerous situation, though per the Japan Times at present, authorities aren't expecting a repeat of the 1914 catastrophe.

Time will tell.

PS: Actually, if you are inclined to buy my DV eBook, thank you and a BIG thanks to everyone who has bought it, but if you hold off for a month or so (no later than mid-September, hopefully), you'll get the much more in-depth second edition that I'm working on now.
 
Last edited:

bjdeming

Member
Sustaining Member
Messages
721
Reaction score
469
Location
Corvallis, Oregon
Many thanks to Hunga Tonga, presumably, for the extended twilight glow; sunset was actually at 7:18 pm!

I've been making every allowance for weather and ash in the air, and still see something on Sakurajima's flank that doesn't shift around:

20220726_060508.jpg

This volcano has a nasty history of flank eruptions, but there is absolutely no mention of a concern about that online, AFAIK, and it would show up on monitors beforehand -- deformation, seismicity, etc.

Am thinking that's probably a forest fire started by some of the big lava bombs from the blast on the 24th.
 

bjdeming

Member
Sustaining Member
Messages
721
Reaction score
469
Location
Corvallis, Oregon
No changes noted in today's update, but they're keeping Sakurajima at Level 5.

With all three summit vents now open, I think it all comes down to how pressurized the magma chamber is. That's miles underground, beyond monitoring range.

The good news: It's always better to have an open conduit, especially at explosive volcanoes, so there no plug to build up pressure behind.

Here's what might be a more reliable live stream:

 

bjdeming

Member
Sustaining Member
Messages
721
Reaction score
469
Location
Corvallis, Oregon
Update: They've dropped to Level 3 per the current update.

That's a big relief, although Sakurajima is still in a new mode, as very slight incandescence showed on the cam overnight.

Much better a lava eruption than escalation into something resembling 1914. Hopefully that will be the only result of this round.
 

bjdeming

Member
Sustaining Member
Messages
721
Reaction score
469
Location
Corvallis, Oregon
Here's another live cam:


Sakurajima is not (yet) going back to its previous vulcanian mode, but it hasn't intensified, either (yet).

The alert level is still 3, but on August 5th, JMA wrote:

There is a risk of eruptions accompanied by large volcanic blocks or small pyroclastic flows over 1 km from the Minamidake summit crater and Showa crater.

So it's still wait-and-see, without evacuations at the moment AFAIK.

Edit: Finally found the "A" cam! :)

 
Last edited:

bjdeming

Member
Sustaining Member
Messages
721
Reaction score
469
Location
Corvallis, Oregon
Well, this is spectacular. Still a vulcanian explosion, but much more powerful than those of the "soccer-game" era. Nice lightning, too. No new updates from JMA.

 

bjdeming

Member
Sustaining Member
Messages
721
Reaction score
469
Location
Corvallis, Oregon
Sakurajima is probably working its way up to trouble but, thankfully, slowly (at least for now). There was no change in JMA's weekly bulletin yesterday.

Now, on a much less potentially disastrous level, something's up in American Samoa.

I haven't heard of either of the volcanoes they mention but will dig up what I can about them and put it into a Sunday Morning Volcano blog post tomorrow (unless something develops in the meantime).
 
Last edited:

bjdeming

Member
Sustaining Member
Messages
721
Reaction score
469
Location
Corvallis, Oregon
Update: Actually, the excellent Volcano Hotspot blog already has these and other Samoan fire mountains covered.

Map-3.jpg


Image source USGS; also, USGS page on Tau.

Smithsonian GVP Tau page. Note that they don't have any eruptive history, but the Volcano Hotspot post describes fresh lava -- probably Pleistocene, I guess. GVP and many other volcanology centers look at eruption activity since the last ice age ended. However, today's USGS Samoan update (linked in previous post) does mention an eruption in 1866 (plus one at Vailulu'u in 2003).

Press release about NOAA briefing on Samoan volcanoes soon after the Hunga Tonga blast, with information about Vailulu'u.

"Eel City and the Moat of Death" (Vailulu'u expedition, 2005, NOAA).

A much drier approach (scientific abstracts) to this very complex volcanic region. (Jargon alert)

GVP Vailulu'u page (this one has activity bulletins, namely, details and images from the 2005 expedition)

It looks like they've processed the Hunga Tonga experience into their public advisories. Volcanogenic tsunamis are rare, but here's what they are now telling American Samoans in today's update:

If there is a tsunami from a nearby volcanic eruption, residents of the Manuʻa islands and elsewhere in American Samoa are more likely to experience natural warning signs before receiving an official tsunami warning.

If you are at the coast, heed the natural tsunami warning signs. If you feel a strong or long-duration earthquake, see a sudden rise or fall of the ocean, hear a loud roar from the ocean, or see a large aerial plume from an eruption, a tsunami may follow, and you should immediately move to higher ground.

Here is information on what you can do to protect yourself and your family if you see a tsunami or receive a warning: https://www.weather.gov/safety/tsunami-during.

Note that they also make clear in the update that it's too early to tell which volcanic center the swarm is coming from; too, such swarms often happen and no eruption follows; and even if there is an eruption, it's not at all likely to resemble Tongan eruptions, which are more explosive.

Their next update, barring sudden changes, will be on the 15th. I'll bet quite a few USGS and NWS employees are working hard this weekend -- and a big "thank you" to them all!
 
Last edited:

bjdeming

Member
Sustaining Member
Messages
721
Reaction score
469
Location
Corvallis, Oregon
Found this video, from 2017, I think, of a recent dive at Vailulu'u.

That dome certainly has grown during the 21st century, but it apparently didn't generate enough seismicity to draw attention like they are giving it and Tau today. ?? How much of that is actual change in seismicity and how much fallout from the January Hunga Tonga blast??

Cool sea critters, though!

 

bjdeming

Member
Sustaining Member
Messages
721
Reaction score
469
Location
Corvallis, Oregon
I did some speculating over at the blog this morning that some folks here might find interesting:

‐--------------------------

No changes, per today’s update.

They’re putting in more equipment, and are detecting 30-60 quakes an hour at present.

The quakes seem to be closer to Ta’ū Island than to the volcano sitting over the hotspot, Vailulu’u, which is interesting.

It’s amazing to see how many agencies are cooperating in this effort, including the Alaska Volcano Observatory as well as HVO, local National Weather Service offices as well as the Pacific Tsunami Center, and even Kiwi volcanological observers.

Probably that’s partly because this site is waaaay out there in the blue latitudes, far from the usual monitoring sources, and a joint operation is necessary (and organized amazingly quickly!)

Also, perhaps, <layperson speculation> it’s because this is a special area of interest. I’ve been doing a little reading (very little, since I’m trying to get this DV eBook revision done ASAP) and have developed a few very vague and ?interconnected? ideas.

Take them FWIW (probably not very much):

• It turns out the Samoan islands are adjacent to — but not, I think, connected to — the northern end of the Tonga Trench subduction zone.

Again, these are totally different from Tongan volcanoes, more Hawaiian style than explosive, but it’s a more complex setting than in Hawaii.

• The Tonga subduction trench is connected to the Kermadec subduction trench farther south: indeed, the boffins sometimes call this the Tonga-Kermadec Trench.

• If “Kermadec” sounds familiar, it might be because this is where there have been a few massive quakes in recent years.

• The tectonic picture here is insanely complicated but awesome — as I understand some of the main action, subduction at the Tonga-Kermadec trench is helping to bring Australia northward, where hundreds of millions of years from now, it will collide with Eurasia as a new supercontinent comes together.

• This sort of thing is going on elsewhere, too (Africa –> Eurasia, for instance), but the geologically recent big Kermadec Islands earthquakes might signify some sort of ongoing step in this Pacific Plate tectonic process, and Earth processes are too big to ignore as well as extremely challenging even for PhDs to understand.

• We just saw a surprisingly massive blast north of the Kermadec trench at Hunga Tonga. That has been plausibly explained by typical volcanic processes, and it very well could be unrelated to everything else, but it’s an item of interest.

• Now, north of the Tonga trench and separate from it AFAIK but close by, and near but apparently not over a hotspot, some unusual seismicity has begun
.


Sure. This complicated business is going to draw international interest from a variety of earth science fields, not because it’s any more of an increased risk to local stakeholders than any other active volcanic complex (nor any less), but because the Earth seems to be up to something new in the south Pacific and, I suspect, no one yet knows what it might be. </layperson speculation>

----

Takeaway: They may still be studying it, but the top minds in science are on this, along with people in various agencies who have decades of experience with eruptions and hazard management. They will keep us informed just as soon as they themselves learn anything.

Those are the ones to listen to and follow, not me or any other sidelines babbler. :)
 
Last edited:

Users who are viewing this thread

Top