Anak Krakatau erupted for more than 24 hours in early September, sending volcanic ash as high as 50,000 feet into the atmosphere, according to ScienceDaily. The ash cloud shut eight airports and disrupted nearly 3,000 flights. Air quality was affected as far away as Jakarta, more than 150 kilometres from the volcano.
Why ash grounds aircraft
Volcanic ash is made of tiny rock and glass particles. Inside a jet engine, those particles melt in the heat and stick to turbine blades, which can cause an engine to stall. That is why aviation authorities close airspace rather than take the risk of flying through a plume. Forecasting where the ash will travel depends on wind, temperature and how high the column rises, and satellite instruments track the cloud in close to real time.
A name with a history
Anak Krakatau means "child of Krakatau." The cone grew inside the caldera left by the catastrophic 1883 eruption of Krakatau, which killed more than 36,000 people, most of them in tsunamis that swept the coasts of Java and Sumatra. The volcano has been restless ever since it emerged from the water in the 1920s. In December 2018, the collapse of part of the cone triggered a tsunami that killed more than 400 people along the same coastlines.
Monitoring a crowded strait
Indonesia's Center for Volcanology and Geological Hazard Mitigation runs a network of seismometers, cameras and tiltmeters around the peak, and it issues exclusion zones that shift with activity. The Sunda Strait is one of the busiest waterways in the region, so an eruption affects more than aviation. Ferries, fishing boats and cargo traffic all have to adjust when the hazard level rises.
Scientists who study the volcano say the pattern of short, explosive bursts is likely to continue. Each event sends a new plume into flight paths, which means airlines and airports in the region will keep building ash contingency plans into their schedules.