"The combination caused a sudden tsunami that hit the coast," Nugroho said, but added that Indonesia's geological agency was working to ascertain exactly how it happened. Indonesian authorities initially claimed the wave was not a tsunami, but instead a tidal surge and urged the public not to panic. Although relatively rare, submarine volcanic eruptions can cause tsunamis due to the sudden displacement of water or slope failure, according to the International Tsunami Information Centre. According to Indonesia's geological agency, Anak Krakatoa had been showing signs of heightened activity for days, spewing plumes of ash thousands of metres into the air. Most recently in the city of Palu on Sulawesi island a quake and tsunami killed thousands of people.

Source: The Nation Bangkok December 23, 2018 06:00 UTC