JAKARTA - The Indonesian authorities raised the threat warning from Bali's Mount Agung volcano to the highest level on Monday (Nov 27) after its eruption intensified.
The country's disaster management agency (BNPB), in a press conference in Jakarta on Monday, warned of the growing risk from lava and mudflows and urged all remaining villagers in the 8km to 10km danger zone to leave.
Thousands have fled from the latest eruptions. BNPB spokesman Dr Sutopo Purwo Nugroho told reporters at the press conference there were 40,000 evacuees now, and expected up to 100,000, which is the estimated population in the danger zone.
The volcano has been belching huge amounts of ash high into the air, forcing Bali's Ngurah Rai airport to close on Monday until Tuesday morning. The airport said in a statement that 445 flights - 196 international and 249 domestic - and 59,000 passengers had been affected.
Bali Governor Made Mangku Pastika said the closure of I Gusti Ngurah Rai International Airport could last longer than 24 hours. "We don't know how long it will be closed for," he told reporters. "Sure, it's been closed for 24 hours until tomorrow, but that doesn't rule out the possibility the (closure) could be extended," Reuters quoted him as saying.
On the neighbouring island of Lombok, the international airport resumed some flights on Monday after it was closed on Sunday due to ash clouds, which are moving now in a more southerly direction. Abrasive ash clouds are a danger to aviation and can badly damage aircraft.
On Monday afternoon, Mr Bagus Wiranata, an information officer at Lombok airport, told The Straits Times that Garuda, Silk Air and Air Asia had decided to cancel flights today to and from Lombok), while Lion Air and Batik Air were still operating.
The nature of the eruptions had now changed, the BNPB has said, with lava now spewing out. Lava is molten rock or magma. On Sunday night, a bright orange glow at the volcano's summit could be seen, signalling that potentially greater eruptions are very imminent, the BNPB said. The agency issued the level four warning alert, which is the highest possible, at 6am on Monday.
Tremors had also greatly increased.
"Eruptions, tremors are continuing until now. Lava is filling up the crater, and will spill over anytime and flow down down the slope," Dr Sutopo told reporters at the press conference on Monday.
But he also said the expected major eruption will not be as large as in 1963 to 1964, the last time the mountain exploded into life in a series of eruptions that killed more than 1,500 people.
"Agung's impending major eruption will not be as big as that in 1963, based on analysis on magma condition, how far ash travels above the crater," he said. "In 1963, ash spewed travelled 20km high, while this time round only 3.5km to 4km (above the crater)."
The volcano, which began to spew lava on Saturday, has continuously ejected ash while the booming sound of intermittent eruptions can be heard as far as 12km away.
Residents have been told to evacuate from the danger zone, which has been expanded to between 8 to 10km from 6 to 7.5km.
Dr Sutopo warned of the risks of hot gases and lahar flows, pointing to the start of the wet season. Lahar flows (sometimes called cold lava) is a type of mudflow or debris flow composed of a slurry of volcanic material and water. Lahar usually flows down along river valleys.
"We have had heavy rain. Eruption material on mountain slope have been swept down, carried by rainwater. This is a secondary threat to residents, in addition to the hot cloud and lava. Some residents have not left danger zones, opting to tend to their livestock," Dr Sutopo told reporters.
All observation stations around Mount Agung have been recording tremendously higher intensity of tremors since Sunday, state news agency Antara reported citing Mr Gede Suantika of the Volcanology and Disaster Mitigation Centre.
"Lava has been flowing out in an inconsistent amount. Sometimes in large amount, sometimes small," he said.
Mount Agung has been rumbling since September, forcing tens of thousands of people to flee to shelters. It began a series of mild eruptions, called phreatic eruptions, last week.
The authorities have been ordered to immediately distribute masks to several villages in affected areas.