Krakatau volcano (Indonesia) Nov 2018 eruption: vulcanian activity
During 20-21 Nov, activity changes significantly: explosions became more rich in ash and contained much less and much less brighter lava bombs. As well, the intervals between individual events gradually increased overall, reaching up to about 2 hours by 22 Nov afternoon although phases of more frequent activity still occurred.
The most likely cause is that the magma column continued to drop internally and thus favored the formation of a more robust blockage, which in turn favored the occurrence of strong vulcanian-style explosions with less fresh incandescent material, but many fragments of the plug. This process is possibly helped at depth by water seeping into the walls of the conduit (so-called phreatomagmatic activity) as the interior pressure dropped.
Visible activity almost completely ceased during the night 22-23 Nov and picked up only again in the afternoon of 24 Nov, when we saw it from the volcano observatory on our way back.
The most likely cause is that the magma column continued to drop internally and thus favored the formation of a more robust blockage, which in turn favored the occurrence of strong vulcanian-style explosions with less fresh incandescent material, but many fragments of the plug. This process is possibly helped at depth by water seeping into the walls of the conduit (so-called phreatomagmatic activity) as the interior pressure dropped.
Visible activity almost completely ceased during the night 22-23 Nov and picked up only again in the afternoon of 24 Nov, when we saw it from the volcano observatory on our way back.
Small, ash-rich explosion on the afternoon of 20 Nov. (Photo: Tom Pfeiffer) [info]
(198 Hits)
(198 Hits)
Ash plume from the same explosion a few seconds later. (Photo: Tom Pfeiffer) [info]
(208 Hits)
(208 Hits)
Beginning of a small explosion. Compared to the previous day, only few bombs are incandescent. (Phot... [info]
(170 Hits)
(170 Hits)
Dark bombs falling out of the ash plume. (Photo: Tom Pfeiffer) [info]
(184 Hits)
(184 Hits)
An eruption seem from 800 m distance. (Photo: Tom Pfeiffer) [info]
(151 Hits)
(151 Hits)
A large glowing block about to land on the slope of the cone. (Photo: Tom Pfeiffer) [info]
(166 Hits)
(166 Hits)
Ash-rich explosion with two large bombs leaving the eruption column on parabolic paths. (Photo: Tom ... [info]
(165 Hits)
(165 Hits)
Base of the ash column during the eruption. (Photo: Tom Pfeiffer) [info]
(164 Hits)
(164 Hits)
Small vulcanian explosion seen from Rakata (night 20-21 Nov) (Photo: Tom Pfeiffer) [info]
(220 Hits)
(220 Hits)
A moderately strong explosion early on 21 Nov. (Photo: Tom Pfeiffer) [info]
(262 Hits)
(262 Hits)
A strong explosion in the morning of 21 Nov: the absence of wind today lets the ash plume rise verti... [info]
(231 Hits)
(231 Hits)
Since the early morning of 21 Nov, the frequency and style of eruptions has changed: intervals are s... [info]
(239 Hits)
(239 Hits)
Ash column rising vertically from the crater. (Photo: Tom Pfeiffer) [info]
(223 Hits)
(223 Hits)
Patrick taking a swim while a vulcanian explosion occurs around noon. (Photo: Tom Pfeiffer) [info]
(239 Hits)
(239 Hits)
In the evening, the eruptions are again a bit smaller and more frequent. (Photo: Tom Pfeiffer) [info]
(190 Hits)
(190 Hits)
The eruptions are all very rich in ash and contain much less of glowing material (compared to the da... [info]
(205 Hits)
(205 Hits)
Incandescent jet of ash and small bombs. (Photo: Tom Pfeiffer) [info]
(224 Hits)
(224 Hits)
Dark ash with embedded glowing material is ejected in the blue hour. (Photo: Tom Pfeiffer) [info]
(219 Hits)
(219 Hits)
Small and brighter eruption after nightfall, but with full moon. (Photo: Tom Pfeiffer) [info]
(206 Hits)
(206 Hits)
A moderately strong eruption seen from Anak Krakatau. (Photo: Tom Pfeiffer) [info]
(217 Hits)
(217 Hits)
Small lightnings occur sometimes. (Photo: Tom Pfeiffer) [info]
(225 Hits)
(225 Hits)
Small eruption with the blue night sky. (Photo: Tom Pfeiffer) [info]
(218 Hits)
(218 Hits)
Suddenly, a stronger explosion fills the full format frame pointed towards the upper part of the con... [info]
(353 Hits)
(353 Hits)
A very large bomb has disintegrated into a trail of glowing rock fragments sliding down the slope. (... [info]
(262 Hits)
(262 Hits)
A second powerful eruption occurs about 10 minutes later. (Photo: Tom Pfeiffer) [info]
(284 Hits)
(284 Hits)
Ash plume rising from the eruption in the previous picture. (Photo: Tom Pfeiffer) [info]
(249 Hits)
(249 Hits)
During the rest of the night, mostly smaller eruptions occur. (Photo: Tom Pfeiffer) [info]
(234 Hits)
(234 Hits)
Ash venting at night. (Photo: Tom Pfeiffer) [info]
(222 Hits)
(222 Hits)
A phase of strombolian-type activity lasts about a quarter of an hour. (Photo: Tom Pfeiffer) [info]
(221 Hits)
(221 Hits)
During the night 21-22 Nov, a few moderately large explosions occur. (Photo: Tom Pfeiffer) [info]
(261 Hits)
(261 Hits)
These vulcanian-type eruptions typically produce ash plumes that rise 1-2 km and eject lots of mater... [info]
(244 Hits)
(244 Hits)
Eruption in the morning of 22 Nov. (Photo: Tom Pfeiffer) [info]
(151 Hits)
(151 Hits)
Generally, the activity has changed a lot by 22 Nov. Longer phases of quiet occur, typically followe... [info]
(158 Hits)
(158 Hits)
A stronger vulcanian explosion sends many blocks behind the old crater rim (lower right in image). (... [info]
(165 Hits)
(165 Hits)
Bombs landing on the southeastern flank of Anak Krakatau, whirling up dust. (Photo: Tom Pfeiffer) [info]
(153 Hits)
(153 Hits)
A small eruption in the afternoon. (Photo: Tom Pfeiffer) [info]
(120 Hits)
(120 Hits)
