DANGEROUS CHILD

Anak Krakatau or "child of Krakatau" emerged from the Krakatau volcano, which in 1888 erupted with such force the blast was heard all the way in Perth, said Mika McKinnon, a geophysicist based in Vancouver, Canada.

Further eruptions have continued from the massive crater left behind.

McKinnon said volcanoes are weak, sloppy heaps of loosely bound rocks all slanted downhill and they slip off all the time.

If this happens to be a large portion, then it would displace enough water to trigger a tsunami.

There are no early warnings systems that can detect such landslide-driven tsunami.

Anak Krakatau is so close to shore there would not have been enough time to react and evacuate the population.

"It's hard to identify landslide-triggered tsunami, especially quickly enough to issue useful warnings," said McKinnon.

"A similar event at Anak Krakatau might trigger another one, or it might not. Maybe a month later, or year from now. We will never know," she said.