On August 27, 1883, the volcanic island of Krakatoa erupted, producing the loudest sound ever recorded by humans. The explosion was heard over 3,000 miles away, rupturing eardrums 40 miles from the site and shattering windows in distant towns.
The sound, estimated at 310 dB, was far louder than any modern jet engine, with the force of 200 megatons of TNT.
This is so astonishingly loud, that it’s inching up against the limits of what we mean by “sound.”
Nautilus has a fascinating description of the absolutely enormous sound produced by the eruption.
“When you hum a note or speak a word, you’re wiggling air molecules back and forth dozens or hundreds of times per second, causing the air pressure to be low in some places and high in other places. The louder the sound, the more intense these wiggles, and the larger the fluctuations in air pressure. But there’s a limit to how loud a sound can get.
At some point, the fluctuations in air pressure are so large that the low pressure regions hit zero pressure—a vacuum—and you can’t get any lower than that. This limit happens to be about 194 decibels for a sound in Earth’s atmosphere. Any louder, and the sound is no longer just passing through the air, it’s actually pushing the air along with it, creating a pressurized burst of moving air known as a shock wave.
Closer to Krakatoa, the sound was well over this limit, producing a blast of high pressure air so powerful that it ruptured the eardrums of sailors 40 miles away. As this sound travelled thousands of miles, reaching Australia and the Indian Ocean, the wiggles in pressure started to die down, sounding more like a distant gunshot. Over 3,000 miles into its journey, the wave of pressure grew too quiet for human ears to hear, but it continued to sweep onward, reverberating for days across the globe. The atmosphere was ringing like a bell, imperceptible to us but detectable by our instruments.”
The eruption triggered massive tsunamis, some over 100 feet high, and killed around 36,000 people. Ash clouds from the eruption blanketed the Earth, creating vivid sunsets and dropping global temperatures by 1.2°C in a phenomenon known as a “volcanic winter.” These changes in the atmosphere lasted for years, affecting weather worldwide.
Krakatoa’s eruption became a global event, reported quickly via telegraph. Its aftermath influenced the study of volcanology, atmospheric science, and sound waves, as the explosion’s sonic waves circled the globe seven times. This extraordinary eruption remains a powerful reminder of nature’s destructive force and lasting impact.
It’s wild to think about the sound traveling so far, and becoming like a weapon as it traveled from the site of the eruption.
The explosion was heard 3,110 kilometres (1,930 mi) away in Perth, Western Australia, and Rodrigues near Mauritius, 4,800 kilometres (3,000 mi) away
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