Sat, 07 Jul 2012 12:46 CDT
Panorama of the summit crater of Anak Krakatau (2 July 2012)
During our recent expedition to Krakatau volcano, we could no longer see the lava dome active during Feb-May this year. Probably, the magma column had dropped in mid to late May and the dome collapsed. At its place, there were only 2 collapse pits, very hot ground and intense degassing from numerous fumaroles inside and outside of the now large summit crater. Seismic activity when visiting the local volcano observatory was at very low levels, suggesting that Anak Krakatau is at the moment in a phase of repose.
Interestingly, a number (at least four) areas with apparent submarine hydrothermal iron-bearing vents were observed that had not been there last year. In these areas, bubbling could be seen in the water, and where accessible, iron-rich greenish warm mud was found at the sea floor, which oxidized to orange when brought to the surface. The sea water around these areas had an intense yellow stain. Very similar submarine activity is known from around Nea Kameni Island, Santorini.