Indonesia on tsunami alert after new cracks appear on Anak Krakatau volcano

The two cracks appeared after the volcano's height dropped from 338m to 110m following its eruptions on Dec 22, 2018. PHOTO: REUTERS

JAKARTA - New cracks have emerged on Anak Krakatau volcano, prompting Indonesian authorities to urge those in the vicinity to be on the alert in case a collapse sets off yet another tsunami.

Dr Dwikorita Karnawati, head of the Meteorology, Climatology and Geophysics Agency (BMKG), told reporters on Wednesday (Jan 2): "Of course the hope is that it will not be like what happened (on Dec 22), but we ask the public to be vigilant when they are in the 500m zone around the coast."

A section of Anak Krakatau's slope collapsed after it erupted that day, sliding into the ocean and displacing massive amounts of water that sent waves up to 5m high crashing into densely populated areas on Sumatra and Java islands.

Dr Dwikorita said the two cracks appeared after the volcano's height dropped from 338m to 110m following its eruptions.

"From the latest we have seen from the air, the mountain is sloping and smoke is rising from beneath the sea water. And on the body of the mountain, we can see from the surface, there are cracks that continue to emit smoke," she said. "The cracks are certainly deep", unlike normal gaps, she added.

The two cracks - which are close to each other - has sparked some concern for her agency.

"What we are worried about is that if there is another eruption, the cracks might connect and weaken the slope, causing part of the mountain to collapse again," said Dr Dwikorita.

The part of the volcano that could collapse has a volume of about 60 million cubic m - smaller than the 90 million cubic m of slope that slid into the Sunda Strait on Dec 22.

Though new cracks have been spotted, Anak Krakatau's volcanic activity has been decreasing, added Dr Dwikorita.

The area around the volcano is still being monitored closely by the authorities.

BMKG last week installed six seismometers dedicated to monitoring the volcano. And Dr Dwikorita said that wave and rainfall sensors had been installed on Tuesday to look at the impact of eruptions on the height of waves.

Meanwhile, the transport ministry is keeping an eye on volcanic ash so that it can decide when flights should be rerouted.

President Joko Widodo spent the first working day of 2019 in Lampung on Sumatra island. It is one of the areas worst hit by the tsunami that left more than 430 people dead and injured over 14,000.

He has asked the Ministry of Public Works and Public Housing to build new housing in the regency of South Lampung, about 400m away from flattened homes. Two hectares of land have been set aside for this.

About 110 people died in the regency. The high death toll was because many homes were right on the beach.

"We will go into the reconstruction and development phase. There will be no temporary shelter," he told reporters. "Housing will be relocated because this location is vulnerable to tsunamis."

Spatial planning along Indonesia's coasts - especially in areas prone to disaster - should be relooked, he added. This could help mitigate the impact of natural disasters.

And the government hopes to include lessons on disaster management at the elementary and high-school levels.

"Disaster education must start this January, especially for regions where there is a high possibility of big disasters," he said.

Join ST's Telegram channel and get the latest breaking news delivered to you.