- Thread starter
- #61
Today’s JMA update (may or may not autotranslate) still shows Sakurajima to be the activity focus around Aira caldera/northern Kagoshima Bay (Kirishima/Shinmoedake, just north of and outside Aira, is still with us but as far as they can tell through weather clouds, it's not doing much more than raising a relatively small plume).
<Layperson speculation>This is really out there, but as mentioned for Shinmoedake in the Volcano Thread, it's not impossible and therefore is concerning.
Aira Caldera feeds magma to Sakurajima, which sits on the south caldera rim (the caldera underlies northern Kagoshima Bay).
Ground levels here sank after the 1914 Taisho eruption, but they have been slowly inflating in recent years until now they are at the same level they were before Sakurajima's 1914 eruption.
That is, roughly the same amount of eruptible magma is now near the surface again, from the same source, as there was just before Sakurajima's VEI 4 in 1914.
However, unlike at the turn of the 20th century AFAIK, Sakurajima has had an open conduit for about seven decades, and through it, has been having more or less constant small eruptions and LOTS of degassing.
That degassing works against Aira's trying to figuratively build up a plinian-style head of steam -- actually oodles of magma-trapped volcanic gases waiting to suddenly exsolve and shatter their confining magma into a soaring plume of ash and tiny glass shards.
But there's plenty of gassy fresh magma available now and so maybe Aira still "wants" another Taisho-sized event.
Maybe it went knocking at the Kirishimayama complex's door. From reading, such as it has been on this very intricate relationship among three volcanoes, I understand that Kirishimayama has its own magmatic plumbing. However, at least a few experts suggest that Aira might have played at least a small role in a few of the complex's eruptions.
So maybe Shinmoedake tried to answer the door when Aira came knocking? This layperson finds it significant that Sakurajima became very quiet for a week or more and then Shinmoedake erupted.
Only the door would not open.
So, on July 6th, something happened somewhere, as indicated by seismograms --
-- and a half-hour later Sakurajima exploded and has been exploding off and on ever since, while Shinmoedake's activity and intensity have dramatically dropped.
Maybe Aira still needs to have a plinian-style eruption and has "decided" that the old site is still the best site?
</layperson speculation>
Please don't take any of that too seriously. I have not seen a single knowledgeable person discussing anything along those lines, and what I think doesn't amount to diddly-squat without academic letters after my name and years of experience under my belt.
Yet it seems logical enough, and if they had such a thing in volcanology, I would be tempted to include "PDS" in all Sakurajima updates right now.
<Layperson speculation>This is really out there, but as mentioned for Shinmoedake in the Volcano Thread, it's not impossible and therefore is concerning.
Aira Caldera feeds magma to Sakurajima, which sits on the south caldera rim (the caldera underlies northern Kagoshima Bay).
Ground levels here sank after the 1914 Taisho eruption, but they have been slowly inflating in recent years until now they are at the same level they were before Sakurajima's 1914 eruption.
That is, roughly the same amount of eruptible magma is now near the surface again, from the same source, as there was just before Sakurajima's VEI 4 in 1914.
However, unlike at the turn of the 20th century AFAIK, Sakurajima has had an open conduit for about seven decades, and through it, has been having more or less constant small eruptions and LOTS of degassing.
That degassing works against Aira's trying to figuratively build up a plinian-style head of steam -- actually oodles of magma-trapped volcanic gases waiting to suddenly exsolve and shatter their confining magma into a soaring plume of ash and tiny glass shards.
But there's plenty of gassy fresh magma available now and so maybe Aira still "wants" another Taisho-sized event.
Maybe it went knocking at the Kirishimayama complex's door. From reading, such as it has been on this very intricate relationship among three volcanoes, I understand that Kirishimayama has its own magmatic plumbing. However, at least a few experts suggest that Aira might have played at least a small role in a few of the complex's eruptions.
So maybe Shinmoedake tried to answer the door when Aira came knocking? This layperson finds it significant that Sakurajima became very quiet for a week or more and then Shinmoedake erupted.
Only the door would not open.
So, on July 6th, something happened somewhere, as indicated by seismograms --
-- and a half-hour later Sakurajima exploded and has been exploding off and on ever since, while Shinmoedake's activity and intensity have dramatically dropped.
Maybe Aira still needs to have a plinian-style eruption and has "decided" that the old site is still the best site?
</layperson speculation>
Please don't take any of that too seriously. I have not seen a single knowledgeable person discussing anything along those lines, and what I think doesn't amount to diddly-squat without academic letters after my name and years of experience under my belt.
Yet it seems logical enough, and if they had such a thing in volcanology, I would be tempted to include "PDS" in all Sakurajima updates right now.