The Sound That Circled the Earth

At two minutes past ten, on the morning of the twenty-seventh of August, eighteen eighty-three, a volcanic island between Java and Sumatra made a sound.

It was the loudest sound in recorded history. People heard it nearly five thousand kilometres away. And then... it went around the world.

The island

Krakatoa sat in the Sunda Strait, the narrow sea lane between Java and Sumatra, in what was then the Dutch East Indies. Steamships passed it every day, and telegraph cables linked the nearby port of Batavia, today's Jakarta, to the rest of the world.

On the twentieth of May, eighteen eighty-three, the volcano woke up. Ash rose six kilometres into the sky. A steamer full of sightseers even sailed out to climb it. For three months it rumbled. Then, on the afternoon of Sunday the twenty-sixth of August, it began to tear itself apart.

The longest night

By two o'clock, a black column of ash stood twenty-seven kilometres high. All night, explosions rocked the ships in the strait. As the eruption peaked, the captain of the Norham Castle, forty miles away, wrote in his log:

So violent are the explosions, that the ear-drums of over half my crew have been shattered. My last thoughts are with my dear wife. I am convinced that the Day of Judgement has come.

The sound

At five thirty the next morning came the first of four colossal explosions. At six forty-four, another. And at two minutes past ten...

In Batavia, a hundred and sixty kilometres away, the pressure gauge at the city gasworks jumped by more than two and a half inches of mercury. That works out to around one hundred and seventy-two decibels. At a distance of a hundred and sixty kilometres.

For comparison: a jet engine at take-off is around a hundred and forty. Sound becomes painful at about a hundred and twenty. And because decibels are logarithmic, every ten more means ten times the intensity.

The sound rolled outward across the ocean. In Perth, Australia, more than three thousand kilometres away, people heard what they took for distant gunfire. And on Rodrigues, a tiny island near Mauritius, four thousand eight hundred kilometres away, the chief of police reported the roar of heavy guns, coming from the east. The sound had been travelling for about four hours.

Around the world

Beyond that, no human ear could hear it. But the wave kept going. In the eighteen-eighties, weather stations around the world recorded air pressure with barographs, a pen tracing a line on a slowly turning drum of paper.

Within hours, sudden spikes appeared on barographs in Calcutta, Mauritius, Melbourne and Sydney. Within twelve hours, Saint Petersburg, Vienna, Rome, Paris and Berlin. Within eighteen, New York, Washington and Toronto.

The wave raced to the far side of the planet, met itself near Colombia, and came straight back. In some fifty cities, the spike returned like clockwork, roughly every thirty-four hours. Over five days, barographs recorded it seven times. The sound of Krakatoa had circled the Earth more than three times.

The wave

But the deadliest part was not the sound. More than two thirds of the island collapsed into the sea, and the eruption drove tsunamis more than thirty metres high onto the coasts of Java and Sumatra. Towns like Merak and Anyer were wiped away.

The official count of the dead was thirty-six thousand, four hundred and seventeen. Other estimates are far higher.

The red sky

Ash and gas had been blasted high into the stratosphere. Within weeks, a fine veil wrapped the globe, and the skies changed. People reported green suns, blue moons, and sunsets the colour of blood.

In late November, the evening sky over New York and New England glowed so red that fire engines were called out in Poughkeepsie and New Haven, to fight a fire that wasn't there. One astronomer has argued that the sky in Edvard Munch's The Scream remembers one of those sunsets over Norway. The following summer, northern temperatures dropped.

The news + the child

The news travelled fast too. Undersea telegraph cables carried it to newspapers in Europe and America within days. It was one of the first disasters the whole world followed, almost as it happened.

Krakatoa itself was gone. But in late nineteen twenty-seven, the sea above it began to boil, and a new island broke the surface. They named it Anak Krakatau, the Child of Krakatoa. It is still growing, and still erupting. In December twenty eighteen, part of it slid into the sea, and the tsunami killed more than four hundred people.

One morning, in one corner of the planet, one sound. And every barometer on Earth felt it.

Key facts

• A gauge at the Batavia gasworks, 160 km away, jumped by more than 2.5 inches of mercury: about 172 dB. source ↗
• The boom was heard on Rodrigues, near Mauritius, 4,800 km away, about four hours later. source ↗
• Barographs around the world recorded the pressure wave seven times over five days. source ↗
• The official death toll, mostly from tsunamis over 30 m high, was 36,417. source ↗
• Red sunsets in November 1883 made fire engines turn out in Poughkeepsie and New Haven. source ↗