Anak Krakatoa or Anak Krakatau or Anak Krakatao is a volcanic island in the Sunda Strait between Java and Sumatra in Indonesia.

Is it possible to interpret warning signals from volcanoes before eruptions and thus save human lives? Yes, according to a research team that studied data from the volcano island Anak Krakatau.

In December last year, volcanic activity caused a large part of the Indonesian island to collapse into the sea, creating a tidal wave that killed around 430 people.

According to the study, there were several minor signs before the eruption that indicated that something was about to happen.

An international research team led by Thomas Walter of the German Research Centre for Geosciences GFZ in Potsdam has now shown that the volcano produced clear warning signals before its collapse.

There were signs that something was going on already in January 2018, they measured seismic activity on the 320-meter-high volcanic island, at the same time as the seismic activity and the number of smaller volcanic eruptions increased a few months before the disaster.

The team used a large amount of data from varied sources collected by ground-based measurements as well as by drones and satellites. The satellite data, for example, showed increased temperatures and ground movement on the southwestern flank, months before the catastrophe.

Seismic data and low-frequency sound waves from a smaller earthquake two minutes before the sudden collapse of a large part of the volcano had heralded the fatal event.

“We used an exceptionally broad range of methods: From satellite observation to ground-based seismic data, from infrasound to drone data, from temperature measurements to chemical analysis of eruption products,”

“Today’s almost unrestricted access to worldwide data was critical in this. In the days following the tsunami, it allowed us to analyze this event at different locations in different countries at the same time.”

– Thomas Walter of the German Research Centre for Geosciences GFZ in Potsdam

Similar to Anak Krakatau such events could also herald themselves on other volcanic islands in the Atlantic, Pacific or even in the Mediterranean, to which the results of the study could then presumably be transferred.

“We assume that tsunami early warning systems must also take into account events caused by landslides. Those volcanoes that are at risk of slipping should be integrated into the monitoring systems.”

– Thomas Walter

Krakatoa is a caldera volcanic island group (Krakatoa Archipelago) in Indonesia, comprising four islands: two of which, Lang and Verlaten, are remnants of a previous volcanic edifice destroyed in eruptions long before the famous 1883 eruption; another, Rakata, is the remnant of a much larger island destroyed in the 1883 eruption.

The study is now published in the journal Nature Communications.


Thomas R. Walter, Mahmud Haghshenas Haghighi, Felix M. Schneider et al. Complex hazard cascade culminating in the Anak Krakatau sector collapse. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-019-12284-5