Krakatau volcano news & eruption updates:
Anak Krakatau volcano (Sunda Stait, Indonesia), activity report
Wednesday Dec 05, 2007 15:15 PM |
Explosion at Anak Krakatau's new crater
We just came back from Krakatau (and Kelud) - here's a summary of our observations on Krakatau:
Night-time eruption of the new crater
During VolcanoDiscovery's expedition, thanks to extraordinary good weather, we were able to observe Anak Krakatau's ongoing eruption during 21-26 November: overall, its activity was relatively constant and ranged from strong strombolian to weak vulcanian activity, probably according to various levels of phreatomagmatic and magmatic activity within the conduit.
All activity occurred from the newly formed crater on the upper southern flank just below the old summit crater of Anak Kraktau. On 21 November, this crater had an oval shape and was approximately 50x70 m in diameter. Reports of lava flows earlier in the course of the eruption could not be verified and no deposits from lava flows were visible, only debris from ejected solid blocks and a few deformed fresh bombs.
The most frequent, typical type of acitivty that was present during most of the time consisted in ash venting. Dense, dark brown brown, billowing ash clouds escaped in pulses from the crater, rose typically 100-200 meter and occurred at near-constant intervals of about 2 minutes. At all times, the ash was drifting east due to near constant westerly winds. Only few or no blocks were observed being ejected along with such ash clouds. On 24 November, we observed phases where ash venting became continous over several minutes.
At more irregular intervals, about 10-30 minutes apart, more violent, small vulcanian-type explosions interrupted the ash venting events. The explosions consisted in a sudden spray of mostly solid rocks and few incandescent scoria, followed by more powerful and turbulent ash plumes, which rose up to above 1 km.
Generally, these vulcanian-type explosions tended to occur after slighly longer repose intervals with no or little visible activity in the crater and in most cases, the length of the repose interval was correlated with the force of the explosion. Several exceptionally powerful explosions occurred at intervals of approximately 16-24 hours: the strongest one occurred happened shortly after midnight on 21-22 November, and showered the whole of Anak Krakatau island with incandescent blocks, ignited bush fires and produced a very loud cannon-shot noise that rattled windows on the west coast 40 km away. Other unusually large blasts occurred at around 2am on 21 Nov, at around 9am and 1:20 pm on 23 November.
Activity shifted temporarily towards more strombolian type explosions on the evening of 22 November: until about 1 am on 23 November, most activity then consisted in bright, scoria-rich strombolian explosions with lots of fresh incandescent bombs that produced only relatively little ash compared to the preivious activity. After some of the more powerful strombolian explosions, we observed weak, near-continuous spattering from a vent in the crater.
Increasing activity after 23 Nov:
Early on 23 November, activity returned to more ash-rich, probably phreatomagmatic in origin, activity. Ash production and the average violence of the individual events increased slighlty but visibly over the next two days, while a rythm of single events at near-constant intervals of about 2 minutes was maintained. During 24-25 November, ash plumes typically rose to >1 km above the crater and were well visible from the west coast.
Photos showing the activity and impressions from the expedition can be found at: www.volcanodiscovery.com/volcano-tours/krakatau/photos.html
Thursday, Nov 15, 2007
Anak Krakatau continues its new strombolian activity from the new vent south of the summit crater. The eruptions are producing small ash plumes, ejections of incandescent spatter bombs as well as lava flows, as news reports and data from KRAKMON indicate. Seismicity was at elevated levels. ... read all
Wednesday, May 18, 2005
As the Volcanological Survey of Indonesia reports, seismic activity at Krakatoa has increased during the past days, and the alert level has been risen to 2 (out of 4). ... read all
Thursday, Apr 14, 2005
Krakatoa volcano in the Sunda Strait between the islands of Java and Sumatra is showing an increased seismic activity as the Indonesian Volcanological Survey reports. Whether eruptive activity is already taking place, is not known at the moment due to bad obvservation conditions, but it is likely that there is or will be activity in the very near future.--- read all