48 comments on “The Sacred Mountain – G. AGUNG, Bali (ID) + ACTIVITY UPDATES + Webcams

  1. Also, the alert level for Ambae volcano (Vanuatu) was raised today from Level 3 to Level 4 (“moderate eruption”) out of 5.

    http://www.vmgd.gov.vu/vmgd/index.php/geohazards/volcano/alert-bulletin

    Aoba, or Ambae, is a massive basaltic shield volcano. A broad pyroclastic cone containing three crater lakes is located at the summit of the Hawaiian-style shield volcano within the youngest of at least two nested calderas. Last significant eruption 2005/06. Lahar danger because eruptions often occur through a large crater lake. May also produce flank eruptions Impressive images at GVP:

    http://volcano.si.edu/volcano.cfm?vn=257030

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  2. From the Indonesian volcano observatory http://www.vsi.esdm.go.id/index.php/gunungapi/aktivitas-gunungapi/1710 via giggle:
    After the status increase to Level III (Alert) on September 18, 2017 at 21.00 WITA, the seismicity of G. Agung continues to show a very significant and unprecedented increase in the history of seismic data recording at Gunung Agung. The volcanic earthquake (VA) that indicates the process of rocks cracking inside the body of the volcano caused by the magma pressure from depth to the surface began to be recorded increasing in number consistently since August 10, 2017 and continues to increase in number after the status increase to Level III (Standby) with amplitude ranges from 4 to 10 mm. Shallow Volcanic Earthquakes (VB) also recorded consistently increased in number since August 24, 2017 with the amplitude of volcanic seismic range between 3-10mm.
    Analysis of the pattern of seismic energy change for this period of Gunung Agung volcano indicates that the increase of seismic amplitude that occurs continues to experience higher acceleration and tends to lead to a line of asymptote (eruption).
    Cross-correlation analysis on ambient-seismic-noise indicates a decrease in the rock velocity structure in the body of Mount Agung. This indicates the destruction zone in the body of the Great Volcano more and more due to magma migration to the surface. If the destruction zone is getting more and more closer to the surface then it is not impossible eruption / eruption can happen soon.

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  3. and under “Instrumental”:
    Post status upgrading to Level III (Siaga) on September 18, 2017 at 21.00 WITA, until 21 September 2017 at 06.00 WITA, recorded 113 times shallow Volcanic earthquake with amplitude 2 – 6 mm and 5 – 14 seconds earthquake. 1947 times In Volcanic earthquake with amplitude 2 – 9 mm, S-P 1 – 3.5 seconds and duration of earthquake 7 – 36 seconds. 85 times a local tectonic earthquake with an amplitude of 5 – 8 mm, a S-P 4.5 – second and an earthquake of 29 – 78 seconds. 1 time earthquake Feels with amplitude 8 mm and long earthquake 66 seconds. 2 times Long tectonic earthquake with amplitude 2 – 9 mm, unreadable S-P and long quake 62 – 147 seconds. The earthquakes were felt increasingly perceived by residents as well as in the Great Volcano Observation Post

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  4. correction: according to John Seach it was oxidation of iron: On 28th May 2006 the colour of Lake Voui had changed from blue to blood red due to oxidation of iron. The change was possible related to a change in the ratio of sulphur dioxide and hydrogen sulphide emitted by vents in the lake

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  5. Thanks Bruce!
    https://www.bnpb.go.id/home/detail/3468/Pergerakan-Magma-Gunung-Agung-Meningkat,-57.418-Jiwa-Mengungsi

    The update of today says that still increasing seismicity indicates magma rising to the surface. Gunung Agung is currently entering a critical phase. [It remains to be seen] if there is enough power for a big push and if it will be able to break down the lava plugs in an eruption.

    The number of refugees until Tuesday morning (26/9/2017) is 57,428 people, i.e. almost all who live in the danger zone.

    Until now Mount Agung has not erupted.

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    • An eruption is looking increasingly likely. The fumaroles observed the other day indicate magma is relatively close to the surface already. Though (like Redoubt years ago, remember?) it could still be years before an eruption occurs. However, maybe there is another parameter we should be looking at in these pre-eruptive phases and that is the vertical length of the magma column. As I understand it, If the column is long its point of neutral buoyancy will be higher, making eruption more likely. Thus the talk of “deep” volcanic earthquakes makes me tend to think an eruption is more likely than not.. though without knowing just how deep these tremors are, it is a pretty moot point.

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      • Adding to this train of thought, when they say that the volcano is now in a critical phase it implies to me that they think the magma column is buoyant enough to reach the surface and the only thing stopping it now is the containing pressure of the country rock inhibiting dyke propagation.

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  6. My thoughts were, how deep might a relatively solid lava plug reach? Certainly not far below the a.s.l. line, as further down it will be broken by tectonic movements. So, how will the pressure from below push out a 3000 m rock column? Magma does not usually take the same path again through solidified rock, but rather makes its way by exploiting cracks and faults at the edge of solid bodies. How will that play out in a volcanic cone, create a new crater, flank eruption?

    OTOH it will be dependent on what exactly the pipe is filled with. If it is mostly pyroclastic materials – ash, lava bombs, fragments of crater wall – the plug might not be as solid, and lava will melt its way through it more easily. It would be helpful to have an idea what exactly the pathway is made of. Obviously, pre-1963 observations don’t exist, so it’s a matter of speculation.

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    • from the paper:
      “In contrast to the limited number of lava dikes, pyroclastic veins are abundant in the conduit zone. It is likely that isolated tremor events reflect formation of cracks in the country rocks, along which volatiles and volcanic ash intruded, before magma ascended along only one vein.”

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  7. btw. this link to Fojin’s paper doesn’t seem to be paywalled: https://www.researchgate.net/publication/279225389_A_5000-year_record_of_multiple_highly_explosive_mafic_eruptions_from_Gunung_Agung_Bali_Indonesia_implications_for_eruption_frequency_and_volcanic_hazards

    from this, we can assume that 75% of the eruptions are smaller than the 1963 eruption and generally involve more mafic magmas than the andesite erupted recently. It will be interesting to see if the next eruption returns to this pattern or repeats the more evolved style of 1963. Either way it doesn’t seem to get much worse than 1963 so if everyone stays outside the exclusion zone it should be a relatively “safe” eruption. Fingers crossed. Volcanoes are fickle. Keep a safe distance, etc.

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