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Mount Agung volcano


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5 minutes ago, Windspeed said:

Seismic activity appears to have increased dramatically over night at Agung.

https://magma.vsi.esdm.go.id/live/seismogram/
b2ffd13a116872d8e97612f86d21ab88.jpg

Someone made a mention of there being more non-harmonic tremors detected...Does that mean anything, or does the current prediction still say "It may erupt, it may not...More likely to erupt than not"? Lol

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3 hours ago, Maestrobjwa said:
Someone made a mention of there being more non-harmonic tremors detected...Does that mean anything, or does the current prediction still say "It may erupt, it may not...More likely to erupt than not"? Lol

 

Non-harmonic tremors are related to the pressurized gases within the magma or conduit, be it water vapor, carbon dioxide, chlorine, fluorine, etc.. These gases are dissolved at depth, however, as magma nears the surface and background pressures decrease, gas bubbles will coalesce in the dyke or conduit. This creates pressure on the surrounding rock and overburden. If we are seeing non-harmonic tremors increasing, we can speculate that the coalescence of these gases are occurring and that the magma is volatile. But this process is not well-understood and the occurrence of non-harmonic tremors do not mean an eruption will occur, it is just more evidence that magmatic processes are occurring within and underneath the volcano. The threat of eruption remains high. But these gases could go on coalescing and the magma could slowly depressurize with time. It is certainly interesting to know there are non-harmonic tremors occurring however and that the magma is probably in a highly gaseous state and any inital eruption(s) probably won't be of the gentle dome variety.

 

LPs and harmonic tremors are probably more what you are looking for that chances of eruption are rapidly increasing, but it's not a perfect indicator. See this great article by Dr. Erik Klemetti:

 

https://www.wired.com/2015/08/whats-quakes-volcano-erupts/amp/

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First drone images from the Thursday, Oct. 19th mission. The article is in Indonesian, but here are the important points. 400 aerial images will be used for 3D modeling to map deformation of Agung's edifice as magma continues to intrude. They also note new solfatara fissure on the southeast crater floor. I assume they are referring to a sulphur crack with sulphuric gases and compounds on the surface around it. Seismic activity also remains very high averaging around 1000 events per day the past few days. All signs still point to an increased threat of an eruption but uncertainty remains for when that may occur. A good lesson in patience for the public and the unpredictable nature of volcanoes. This could go on for weeks to months.

http://amp.kompas.com/regional/read/2017/10/19/20271871/terbangkan-drone-bnpb-sebut-rekahan-gunung-agung-semakin-luasb702621b67d04ffe7b14b72399cfc5f2.jpg3113ff75b64e250ecd3de83fac4526cd.jpg

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Nice to see GPS and seismic instrumentation from the USGS being put to work to help improve accuracy of seismic activity with Mount Agung:

On October 18, 2017, the G. Agung Emergency Response Team conducted the Installation of seismic stations at CEGI GPS Station and integrated with USGS GPS equipment. Signal Radio is first transmitted to Repeater Station in G. Abang and from Repeater G. Abang forwarded to Pos PGA Agung in Rendang Village. This installation is done to get seismic and GPS networks much better than before, so that G. Agung is in seismic polygon which is very useful for accurate determination of types of earthquakes, hypocenter and other seismic analysis related to G. Agung's still very high activity.


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Hopefully it’s boom goes the dynamite sooner than later.
Hopefully the initial eruption is not much more than a large belch and the volcano begins a less explosive lava dome / flows cone building stage similar to Mount St. Helens' 2004-2008 activity.

 

Bali is heavily populated and is extremely dependent on tourism and agriculture. Being one of the more sought after holiday destinations in Indonesia, much of the growth in population is due to the tourism industry's growth there over the past 30 years. A large scale eruption like 1962 would be an economic disaster and inevidably a humanitarian crisis. We've had enough of those for one year (Lesser Antilles, Puerto Rico, Yemen, Syria, etc.). But I digress... Anything is possible. Best case, no eruption or small eruption and a nice spectacle for the natives. Worst case, the entire island is covered in ash. Actually, worst case would be bad for more than Bali. But that's a far lower probability than no eruption at all.

 

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Overall mean seismicity has dropped significantly over the past three days to around 200-300 events/day versus the 700-1000 events/day over the past few weeks. That is still well above background levels however. PVMBG notes inflation of 6 cm of the upper edifice and is still occurring. Rock fracturing has just decreased, which can't necessarily be interpreted as a sign of decreased threat; to say they are not sure of interaction with overburden and rock fracturing. The fissure in the crater has also expanded.

https://coconuts.co/bali/news/balis-mount-agung-volcano-still-highest-alert-level-eruption-despite-decline-seismic-activity/amp/
 

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The alert status of Mount Agung has been downgraded to level 3 Alert Standby from highest level 4 Danger. The restricted area has also been decreased from 12 to 6 km from the summit crater. As such, some Balinese are returning home. This does not mean that an eruption will not occur, it just means due to a significant decrease in seismic activity and degassing, the threat of an eruption large enough to impact those locations may be decreasing. Good news but the situation is still fluid and the alert level could just as easily be upgraded if seismic activity ramps back up or signs of actual eruptive acitivity begin.

https://coconuts.co/bali/news/thousands-evacuated-balinese-slowly-make-way-back-home-alert-level-mount-agung-downgraded/

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  • 3 weeks later...

Wow...So after weeks of declining seismic activity...finaly some action!! (I never knew volcanos could be so unpredictable!) So you said the "old plug"...is that basically the "seal" from the previous 1963 eruption?

6 hours ago, Windspeed said:

Mount Agung appears to be producing phreatic eruptions with light ash emissions. A volcanic tremor is also evident on seismometers. The old plug may finally be breaking down on the crater floor.

 

 

 

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Wow...So after weeks of declining seismic activity...finaly some action!! (I never knew volcanos could be so unpredictable!) So you said the "old plug"...is that basically the "seal" from the previous 1963 eruption?

 

Yes, I'm referring to the old igneous rock layers / plug / seal left over from the previous eruption(s). Yesterday's event appears to have been phreatic in nature.

 

Ground water gets superheated in the volcano and vents as steam from fumaroles at the surface. As new magma rises in the edifice or conduit, the upper region of the volcano heats up. We have seen that over the past month with a nearly constant steam plume. Sometimes the water near the surface of the crater in the old rock layers will flash to steam rapidly, causing violent pressurization and leading to explosions. Old rocks get blasted out and even pulverized to ash. These are phreatic eruptions.

 

Phreatic eruptions generally do not include ash from a new magma source but can precede new lava. They do not mean a larger eruption is going to occur however. Such activity needs to be closely monitored though as continued phreatic activity can also further fracture, weaken and destabilize the upper conduit, preceding or even leading to an actual eruption if new lava.

 

Volcanologists will need to sample the new ash emissions to see if there are signs of cuspate revealing bursting bubbles that represent new magma.

 

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Incandescent light is being emitted at Agung's summit on the visible night camera reflecting off the ash column. This is a sign of very hot material is being ejected inside the summit crater, and as such, Agung may be erupting fresh lava. A low seismic signal is evident and a 4700 meter ash plume is currently drifting SSW per VONA Aviation warning.

Here is a still:
fabf219d6c36c61e8d3a5e95a49085cd.jpg

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3 hours ago, Windspeed said:

Incandescent light is being emitted at Agung's summit on the visible night camera reflecting off the ash column. This is a sign of very hot material is being ejected inside the summit crater, and as such, Agung may be erupting fresh lava. A low seismic signal is evident and a 4700 meter ash plume is currently drifting SSW per VONA Aviation warning.

Here is a still:
fabf219d6c36c61e8d3a5e95a49085cd.jpg

Lava flowing

 

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1 hour ago, Windspeed said:

Yes, no doubt the eruption has become magmatic. Color imagery there clearly shows a red glow emitting from the summit crater:

Whoooaaaa buddy....Might be inching ever closer to showtime! And Dr. Krippner posted this article a couple days ago....Mt. Agung seems to be following the pattern for volcanos that haven't erupted in decades!

https://www.earthmagazine.org/node/21527

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On 9/26/2017 at 2:29 AM, raindancewx said:

I saw a quote from some of the older people near Agung, who survived the 1963 eruption, they said essentially they think it will erupt, but not for a few months. Will be interesting to see when/if it does. It's interesting looking at the AMO values in 1963, big crash almost immediately after Agung erupted in March, but it may be a coincidence.

It has been a while for a 5 or greater eruption in the tropics (23S to 23N), last one was Pinatubo in 1991. Wikipedia has five eruptions that were VEI 5 or higher in the tropics from 1900-1999. 

The VEI scale page on Wikipedia implies the sixes are once to twice a century, fives are once every 12 years, with the fours every 18 months. Only one five since 1991 though, and it wasn't in the tropics.

Suspect the old people in the article will end up being correct. Would be interesting to see what is similar and what is not from their perspective to the 1963 eruption.

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