Indonesia's Krakatau volcano shrinks by two-thirds after collapse triggered killer waves last week

(Top) Anak Krakatau, before the Dec 22 eruption. The relatively flat background is Sertung island. (Above) After the Dec 22 eruption, Anak Krakatau (pink line) is lower than Sertung island (red line). Yellow arrow is the height of Sertung island.

JAKARTA - Anak Krakatau has lost about two-thirds of its height and three-quarters of its mass since the Dec 22 eruption that spawned a deadly tsunami, leaving more than 400 people killed and thousands injured, Indonesia's national geological agency told a media briefing on Saturday (Dec 29).

The agency was able to carry out visual checks near the erupting volcano after the bad weather subsided on Friday. The volcano lies in the Sunda Strait separating Java and Sumatra islands.

Based on photographs taken of Anak Krakatau, researchers confirmed that the huge landslides took place at Anak Krakatau following the Dec 22 and subsequent eruptions, resulting in a sharp decline in its height from 338 m to 110m, said Mr Antonius Ratdomopurbo, the agency's secretary.

"There is now a small potential for Anak Krakatau to trigger another tsunami," Mr Antonius added.

A section of the volcano's slope collapsed after the Dec 22 eruption and slid into the ocean, which displaced massive amounts of water, generating giant waves up to 5m high that then inundated the nearby coastlines of Java and Sumatra.

The Anak Krakatau volcano now has an estimated mass of about 50 million cubic m, or about 20 to 25 per cent of its original size, Mr Antonius said.

He added that the agency would continue to monitor the volcano's activities in the coming days before reviewing its current alert status.

On Thursday, the danger alert for Anak Krakatau was raised to three, the second highest on the four-level scale. A no-go zone around it has been expanded from 2km to 5km.

The volcano, whose name means "child of Krakatau", has been rumbling on and off since July but has been particularly active since the weekend.

The volcano has increased its activities in the past few days, spewing high columns of ash of up to 3,000m that fell on nearby cities even as aid workers and rescuers struggle to reach communities reeling from the devastation wreaked by last Saturday's killer waves.

At least 426 people have been killed, over 7,000 others injured and another 23 still missing in the third major natural disaster to hit Indonesia this year.

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