Anak Krakatau, a volcanic island in Indonesia's Sunda Strait between Java and Sumatra, erupted early Sunday, forcing the cancellation of all flights at Jakarta's Soekarno-Hatta International Airport and disrupting operations at other domestic airports as ash drifted across western parts of the country.

Indonesia sits on the Pacific Ring of Fire and is home to more than 100 active volcanoes, making eruptions a recurring test of the country's disaster monitoring and aviation systems.

According to Indonesia's Geological Agency, the volcano had shown signs of activity since Friday before erupting for 30 seconds at 3:53 a.m. Sunday and again for 16 seconds about three hours later. Closed-circuit camera footage captured lava flares from the volcano.

No casualties were reported and no evacuation order was issued. The nearest settlement lies more than 16 kilometers (10 miles) away, but authorities warned residents and visitors to stay at least 3 kilometers (2 miles) from the active crater.

Volcanic ash spread across parts of Jakarta and Lampung province, at the southern tip of Sumatra, according to Indonesia's Center for Volcanology and Geological Hazard Mitigation.

AirNav Indonesia closed airspace around Soekarno-Hatta and Halim Perdanakusuma airports in Jakarta, along with six other airports, including Radin Inten II Airport in Lampung, due to volcanic ash. Volcanic ash poses a particular hazard to aviation because abrasive particles can damage aircraft engines, windshields and fuel systems, which is why ash advisories routinely trigger large-scale airspace closures even when eruptions occur far from runways.

By Sunday evening, the closure of eight airports had affected 170,000 passengers through 1,558 canceled flights, including 963 at Soekarno-Hatta alone. All eight airports were ordered to remain closed until 8:59 a.m. Monday.

"It's of course an inconvenience," said Diego Urdiales, a Spanish tourist who had been scheduled to fly home to Madrid. "I was supposed to get input from the airline … but so far no news."

"It's a natural disaster, it's a force majeure, so, what can we do?" said Michele Gouw, an Indonesian passenger. "We just have to accept it and wait for the airline and airport directions."

Indonesia's Directorate General of Civil Aviation said it was closely monitoring the eruption's impact on air travel and coordinating with airlines, airport operators, air navigation services and the meteorology agency.

"Safety remains our top priority in every operational decision," Lukman F. Laisa, the Ministry of Transportation's director general of civil aviation, said in a statement.

Laisa warned that flight schedules could face cascading disruptions affecting aircraft rotations, fleet availability and terminal capacity as airlines work to restore operations.

The eruption also disrupted services at Bali's I Gusti Ngurah Rai International Airport and at Medan.

Using satellite imagery, Indonesia's volcanology agency and the Darwin Volcanic Ash Advisory Centre identified two ash clouds. One plume rose to 20,000 feet (6,100 meters) and drifted northeast over Jakarta, Banten, West Java and nearby waters. A second cloud reached 50,000 feet (15,200 meters) and spread over parts of Banten, Lampung and Bengkulu provinces, the southern Sunda Strait and sections of the Indian Ocean west of Sumatra.

Lana Saria, head of Indonesia's Geological Agency, said activity at Anak Krakatau has intensified since July, with Sunday's eruption the strongest during that period. The repeated eruptions indicate a continued supply of magma and volcanic gases beneath the volcano, she said, though officials cannot predict whether a larger eruption will occur.

"We continue to evaluate the volcano's development based on all monitoring data, not solely on the number of eruptions or the height of the ash column," Saria said in a video briefing.

She identified the main hazards as volcanic ash, high concentrations of gas, and the ejection of hot rocks and other material around the crater area.

The eruption's impact extended beyond air travel. On Sunday, the government authorized schools in areas affected by volcanic ash to temporarily shift to online learning at home. The measure is intended to reduce students' exposure to ashfall and allow local authorities to adjust classroom activities based on conditions on the ground. Volcanic ash can irritate lungs and eyes, and health authorities commonly advise affected residents to wear masks.

Anak Krakatau, which means "child of Krakatau," is the offspring of the famous Krakatau, whose monumental 1883 eruption triggered a period of global cooling. The 1883 event, one of the most destructive volcanic eruptions in recorded history, killed tens of thousands of people and was heard thousands of kilometers away.

An eruption of Anak Krakatau in 2018 caused a tsunami that killed at least 430 people in Sumatra and Java. Researchers believe volcanic activity triggered an underwater landslide, causing a large chunk of the volcano's southwest slope to collapse and displace a large volume of water. Scientists said Anak Krakatau island was only about a quarter of its original size after that eruption.

Source: Fortune