A booming eruption at Indonesia’s Anak Krakatau volcano lasted more than 24 hours in early September, hurling ash and volcanic gas high enough into the atmosphere to ground flights across Jakarta and disrupt travel for hundreds of thousands of passengers. The eruption marked one of the more forceful outbursts from the young volcano in years, closing airports on two of Indonesia’s most populous islands and coating parts of the capital in ash. Officials say the immediate crisis has passed, but the volcano remains on close watch.
A 24-Hour Eruption Between Java and Sumatra
Anak Krakatau sits in the Sunda Strait, the channel separating Java and Sumatra, and erupts periodically as a matter of routine. What began late on September 4 turned into something far more disruptive: a continuous, explosive eruption lasting more than a day that sent gas and ash surging into the sky, captured in satellite images taken with the Landsat 8 and Suomi NPP spacecraft. Indonesia’s meteorological and geophysical agency, BMKG, reported that ash reached altitudes of roughly 6,000 meters, or about 20,000 feet, to the east of the volcano, and as high as 15,000 meters, or roughly 50,000 feet, to the west, drifting over Sumatra and parts of Banten province on Java. Residents as far as 435 miles away reported hearing the volcano’s booming sounds.
Ash Grounds Jakarta’s Airports
The ash cloud forced the temporary closure of eight airports across Java and Sumatra, including Soekarno-Hatta International, Indonesia’s busiest, and Halim Perdanakusuma, both of which serve greater Jakarta, according to NASA’s Earth Observatory. Transport officials said the disruption affected close to 3,000 flights and left more than 270,000 passengers stranded at the height of the shutdown, a figure that grew past 340,000 once delays and diversions at smaller regional airports were included, according to Al Jazeera. Volcanic ash is especially hazardous to aircraft because the fine glass-like particles can damage jet engines and abrade windshields, so carriers grounded flights rather than risk flying through contaminated airspace. Unlike ordinary dust, volcanic ash is made of pulverized rock and glass that does not burn away in a jet turbine; instead it melts inside the superheated combustion chamber and can re-solidify on turbine blades, choking airflow and, in the worst documented cases, causing engines to lose power entirely mid-flight. That risk is why aviation authorities favor grounding entire fleets over trying to route around a drifting cloud that satellites and radar can struggle to track precisely. Airports in Semarang and Surabaya were held in reserve as alternative landing sites while the main hubs remained closed.
Cloud-Seeding to Wash the Ash Away
With the eruption’s most explosive phase easing by September 6, Indonesia’s disaster mitigation agency, known as BNPB, said it would attempt cloud-seeding to induce rainfall and clear lingering ash from the air over Jakarta and surrounding areas. “If it rains heavily enough, the volcanic ash that has been disrupting our daily lives since yesterday and continuing today will be washed away quickly,” BNPB chief Suharyanto told reporters, according to Al Jazeera’s account of the news conference. Schools across Jakarta shifted to online classes while the ash hazard persisted, and ashfall affected populated areas east of the volcano, including parts of West Java, prompting health warnings about the ash irritating skin, eyes and the respiratory tract.
A Volcano Born From Krakatoa’s Catastrophe
Anak Krakatau, whose name translates to “Child of Krakatau,” emerged from the sea in the 1920s inside the caldera left behind by the catastrophic 1883 eruption of Krakatoa, one of the deadliest volcanic events ever recorded and one whose explosions were reportedly heard thousands of miles away, an account still cited by volcanologists as a benchmark for how far the sound of a major eruption can travel. The young volcano has a history of sudden, dangerous collapses: a 2018 eruption caused part of its crater to slide into the sea, triggering a tsunami that killed more than 400 people along the coasts of Java and Sumatra. That history is why authorities barred ships from approaching within a three-kilometer radius of the volcano during the latest activity and asked vessels transiting the strait to stay alert for navigation hazards, even though officials said this eruption carried no imminent tsunami risk.
Indonesia Has Seen This Kind of Disruption Before
Jakarta’s shutdown fits a pattern aviation regulators around the world have dealt with repeatedly whenever a volcano sends ash into busy air corridors. Indonesia sits on the Pacific “Ring of Fire” and is home to more active volcanoes than almost any other country, so its aviation authorities have built playbooks specifically for ash-related closures, including designated alternate airports and standing coordination with the country’s Volcanic Ash Advisory Center, which tracks plumes and advises airlines on which routes to avoid. The broader lesson is not unique to Indonesia: a major European eruption in 2010 grounded flights across an entire continent for roughly a week after ash drifted into some of the world’s busiest airspace, an episode still referenced by regulators as the clearest example of how a single volcano can ripple through global air travel far beyond the region where it erupts.
Airports Reopen, but the Alert Stays Elevated
By September 8, the continuous explosive phase had subsided and the volcano had settled back into a more typical pattern of intermittent, smaller Strombolian bursts of ash and lava, and the closed airports resumed normal operations. Even so, Indonesian authorities kept Anak Krakatau at the second-highest level on the country’s four-tier alert scale, a status it has held since early July, meaning access remains restricted and monitoring continues around the clock. The episode is a reminder of how quickly a geologically active corner of Southeast Asia can reach across an ocean and disrupt air travel, ashfall and daily life for a metropolitan area of more than 30 million people, even when the volcano itself sits many miles offshore.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
More from Morning Overview
