In the first days of September, in the villages near the Sunda Strait, people came out of their houses with brooms. They swept grey dust from their floors and cleaned the blackened walls of a nearby mosque. Reuters photographers found them doing this work while the volcano was still erupting. At night, the lava from Anak Krakatau turned the sky red.
The volcano began to erupt on the Saturday and threw up a fountain of lava. According to Indonesia’s geology agency, people in several parts of the country heard loud booms and felt the ground shake. At half past one on Sunday morning, after ash was found in the air around the airport, Soekarno-Hatta International Airport stopped all flights. The transport ministry said a test had shown that volcanic ash was spreading over the airport area, so the closure continued until half past nine that morning. The ministry counted 209 flights affected and more than 22,000 passengers. Flights to and from Singapore had the biggest problems, and routes to Doha, Sydney and Kuala Lumpur were also disrupted. Local airport staff counted at least sixteen domestic flights to Bali that were cancelled.
The airport did not stay open for long. On Monday morning the transport minister said that seven Indonesian airports were still closed because of the ash, and two of them serve Jakarta. Ash had covered the capital and several areas around it since the eruption started late on Friday, and the airports were closed for safety reasons.
In this part of the world, that word “safety” has a history. On the night of 24 June 1982, a British Airways Boeing 747 called City of Edinburgh was flying from Kuala Lumpur towards Perth when it flew into ash from Mount Galunggung, about 110 miles south east of Jakarta. The weather radar was made to find water, and the ash cloud was dry, so the screen showed clear skies. Smoke came into the cabin and smelled of sulphur, and passengers who could see the engines saw them shining a strange bright blue. Then all four engines stopped. The crew worked out that they could glide for twenty three minutes from 37,000 feet, and Captain Eric Moody told the passengers that the plane had a small problem, that all four engines had stopped, and that the crew were doing their best to start them again. Many passengers wrote notes to their families. At 13,500 feet the engines started again, one after another. The windscreen was now like frosted glass, so the crew landed at Halim Perdanakusuma almost completely on instruments.
The investigation later explained why. The ash took oxygen away from the engines, damaged the windscreen and blocked the machinery, and inside the engines it melted and stuck to the metal. Jet engines work at 1,200 to 2,000 degrees Celsius, which is hot enough to melt ash. Every volcano produces ash with a different chemical mix, so each ash melts at a different temperature, and researchers have heated samples in a laboratory to build a model that predicts when this will happen.
Airports usually close instead of sending planes around the cloud, because nobody knows exactly where the cloud is. Very small particles fall much more slowly and travel much further than larger ones, and scientists cannot easily know what sizes the volcano has produced.
Europe learned how expensive this uncertainty is. On 14 April 2010, water from the Eyjafjallajökull glacier met hot magma in Iceland. The explosion sent very fine ash into the jet stream, it spread quickly over Europe, and air traffic stopped for days. On the Thursday, between 5,000 and 6,000 of Europe’s 28,000 daily flights were cancelled, and at Heathrow’s Terminal 4 every check in desk was closed. Passengers who could not travel were given camp beds at Frankfurt, and in Copenhagen fewer guests came to Queen Margrethe’s seventieth birthday. Jerry O’Callaghan, fifty, from Cork, was coming home from a holiday in America when his flight was cancelled. He said the airlines should have better equipment, because it was only a load of ash.
The volcano above Jakarta has a far more violent past. When Krakatoa exploded on 26 and 27 August 1883, more than seventy per cent of the island was destroyed. The third explosion is still the loudest sound in history, heard 3,110 kilometres away in Perth, and at least 36,417 people died in the eruption and the waves that followed. The new cone first appeared in 1927 and stayed above the sea from 11 August 1930, growing seven to nine metres a year. On 22 December 2018 its south western side slid into the sea, two minutes after a small earthquake, and the tsunami killed 430 people.
In 2010, an Icelandic geophysicist named Einar Kjartansson was asked how long the trouble would last. He said the ash would keep coming for days or weeks, but whether it ruined anyone’s travel was a question of weather: “It depends how the wind carries the ash.”