8 comments on “Flank Collapse at Anak Krakatau, Dec. 22, 2018

  1. Thank you agimarc, great summary of the events!

    Øystein posted a wonderful comparison today: one of his and a new one by James Reynold taken from the same direction. He says:
    “Image-comparison of Anak-Krakatau before and after collapse, showing the major changes to the volcanic Island. First photo captured 5th August and second photo taken by @EarthUncutTV today [11/01/2019] 1/3. Hadn’t it been for the Island of Sebesi in the background (North) and Lang Isl. to the right (East) it would have been difficult to recognise it’s the same place. The changes at Anak-Krakatau are major as this comparison shows. 2/3 It is also interesting to note, that the prominent yellow/brown water discoloration visible now after the collapse, were also present on SW coast, altough weaker, pre-collapse in August! 3/3”

    Volcanologist Fumihiko Ikegami (@fikgm) explains the colouring: “Highly acidic hotspring water is likely upwelling at the vent (white colored). The water has obtained lots of irons from rocks at its undergroud passage. When the water and seawater get mixed, it gets less acidic and the irons begin precipitating as iron hydrooxides (in orange)”.

    So, was the discoloration in August already a sign of the possible new vent/conduit that migh have weakened the cone up to the collapse? At least it’s a sign of hydrothermal emissions in that place, I suppose such cracks can then lead to phreatic or phreatomagmatic explosions.

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    • Well I’ll be. The secondary vent started showing in August and nobody caught it. The notch ends up being where the steaming is coming from in August. Impressive. What a system. Cheers –

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      • The side vent is clearly visible on this overflight today, in the beginning of the video. It seems to be just a hydrothermal vent so far, but may still have caused the main phreatic explosion.

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  2. Momotombo: There seems to be quite heavy steam emissions from this fumarole near the geothermal plant. The left image is from 05:20 LT last night. It had started 7 minutes earlier but then this cam got stuck. On the right, the plume can be seen rising behind the slope, this at 09:48 LT. Just so we don’t forget that Momotombo “is an active volcano” as the Japanese say in their level one hazard warning 😉

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  3. Interesting, “these maps (from Thornton and Rosengren, 1988) show AnakKrakatau the last time it hosted a crater lake, in 1931-52. The crater lake was filled in by lava flows and tephra in 1960-63.” (S. Carn) This looks almost the same as now:

    The paper where this comes from may be interesting to read too, even though it’s named “Zoological expeditions to the Krakatau Islands, 1984 and 1985, …” it has a lot about eruptions and the geological history:

    https://royalsocietypublishing.org/doi/pdf/10.1098/rstb.1988.0126

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  4. Pingback: Guest Reblog: The Anak Krakatau Flank Collapse – Flight To Wonder

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