Anak Krakatau

Anak Krakatau is perilously perched on the flank of the 1883 caldera. It is possible that the main threat posed by Anak Krakatau at the present time could be the generation of tsumanis by failure of parts of the SW flank. It is suggested that a small such failure caused the 2m high tsunami experienced on Rakata during the night of 19-20 october 1981, when Krakatau once again started a new eruption sequence (Camus et al., 1987. J. Volc. Geotherm. Res. 33, p.299-316). No collapse scar was noted so the event was presumably entirely submarine. For discussion of the generation of tsunamis by partial flank collapses, the reader is also referred to the sections on Stromboli and Augustine volcanoes. Much of the base of Anak must rest on a sloping layer of loose pyroclastic material from the 1883 eruption. Nevertheless, the SW flank is today supported by the flat bottom of the 1883 depression. Hence, a large-scale collapse seems unlikely.
It should be mentioned that the islands of the Krakatau complex and particularly Anak Krakatau have provided a model system for numerous studies on the reintroduction of plant and animal life into an initially more or less "biologically sterile" environment. These studies will however not be discussed here.
During eruptive phases, tourists are usually supposed to stay at a distance of 3km from the active cone and landings on Anak Krakatau are prohibited. These rules do not however appear to be strictly adhered to. Visitors should be aware of the risks associated with the type of activity commonly observed at the volcano as are illustrated in the photos below.