To the left – a satellite image from December 17 before the activity
To the right – a satellite image from December 30 – note the large bay in the middle of the left (west) edge. From a certain perspective it probably remarkable that there is anything left above the surface (or below) of the volcano at all.
For bold biologists – there MAY be an opportunity now similar to the situation in the 1930s. It seems likely that Anak Krakatau – if it survives – is largely devoid of plants and animals so recolonization can be observed. Drones should be considered – they are cheap, expendable and do not leave footprints or litter.
Among the challenges – how much danger is there that some or most of the remaining volume will be the basis for another explosion. If any subsequent explosion is less than let’s say VEI=2.5, except for the remaining island possibly disappearing, there might well be no consequences for nearby coastlines. It is not clear, so as to speak, whether the new bay has brought significant amounts of seawater and magma into contact. If not, does a continued west-east fracture present a danger – or in the future would the two ‘halves’ of the island simply crumble peacefully into the sea. Anak Krakatau has been expanding since at least the 1920s – perhaps even right after the 1883 eruption. Note that ash clouds reached 40,000 feet January 2nd so it is worth keeping a close eye on the Sunda Strait. The consensus currently seems to be that the current volcano started from the [submerged] floor of the caldera scooped out in 1883. Of concern would be how stable Cucu Krakatau (Anak = child; Cucu = grandchild) might be if it rises on the remnants of Anak Krakatau.
During the December event ash emissions reached 60,000 ft. The tsunamis struck Tanjung Lesung Beach, Sumur Beach, Teluk Lada Beach, Panimbang Beach, and Carita Beach. I would imagine more locations will be added. The eruption had a volcanic explosivity index (VEI) of 4. So far, the estimates are that the volcano’s height above sea-level went from 338 to 110 meters. The volume of rock displaced is estimated at 150-180 million cubic meters. Currently, the numbers reported are 431 people killed; 7200 injured; 48,000 displaced; 1,600 houses heavily damaged; and over 400 marine vessels damaged. No report yet of any damage to a major ship. It is reasonable to expect all those numbers to increase. There has been no estimate of economic damage so far.
Note that, on average only one eruption per year worldwide has a magnitude of VEI=4 or greater.
Also note that the eruption of August 27, 1883 was far more powerful: more than 18 BILLION cubic meters of ash to a height of 80 km and a tsunami as high as 30 meters along the west coast of Banten and south coast of Lampung. The tsunami struck almost 300 villages and killed over 36,000 people. A reasonable guess of the population for Indonesia in 1880 would be 40 million. That means six times as many potential human targets today. The Krakatau complex has a long history of activity – 2017, 2007-12, 2001, 2000, 1999, 1997, 1996, 1994-95, 1992-93, 1988, 1981, 1980, 1979, 1978, 1975, 1972-73, 1969?, 1965?, 1959-63, 1958-59, 1955, 1953, 1952, 1950, 1949, 1946-47, 1946, 1945, 1944, 1943, 1942, 1941, 1938-40, 1937, 1936, 1935, 1932-34, 1931-32, 1927-30, 1883, 1680-81, 1550, 1350, 1150, 1050, 950, 850, 416, 250.