The 1883 eruption of Krakatoa, a volcanic island situated in the Sunda Strait of Indonesia, stands as one of Earth’s most powerful volcanic events. On August 27, 1883, its climactic explosion obliterated over 70% of the island, reshaping the local geography. This cataclysmic event, classified with a Volcanic Explosivity Index (VEI) of 6, unleashed immense forces that had widespread and lasting effects across the globe.
The Deafening Roar
The sound generated by Krakatoa’s main explosion has been widely recognized as the loudest ever recorded in human history. At a distance of 100 miles (160 km) from the volcano, the sound was estimated to be around 180 decibels (dB), though some calculations suggest 172 dB. A jet engine at close range typically produces about 150 dB, and the human pain threshold is approximately 130 dB. This means the eruption’s sound near the source was far beyond what humans can comfortably endure.
The sheer intensity of the blast had immediate and severe physical consequences for those nearby. Sailors on ships about 40 miles (64 km) from Krakatoa experienced ruptured eardrums due to the immense pressure wave. In Batavia (modern-day Jakarta), approximately 100 miles (160 km) away, the air waves were strong enough to shatter windows and crack walls. Anyone within 10 miles (16 km) of the eruption would have likely suffered permanent deafness. The sound pressure was so extreme that it transcended normal acoustic vibration, transforming into a shock wave exceeding 194 dB, which is considered the theoretical maximum for sound in Earth’s atmosphere.
Journey of the Sound Waves
The sound of the Krakatoa eruption traveled an extraordinary distance, reaching across continents and oceans. Reports confirm the sound was heard over 3,000 miles (4,800 km) away. In Perth, Western Australia, about 1,930 miles (3,110 km) away, residents clearly heard the explosion. The blast was perceived on Rodrigues Island in the Indian Ocean, nearly 3,000 miles (4,800 km) distant, where it was mistaken for cannon fire from a nearby ship.
The sound waves propagated globally, circling the Earth multiple times. Atmospheric conditions allowed these powerful waves to travel such vast distances, with the sound reaching faraway locations approximately four hours after the eruption due to the speed of sound.
Scientific Measurement and Aftermath of Sound
The global passage of the Krakatoa sound was scientifically documented. Barographs, instruments recording atmospheric pressure, registered significant fluctuations as the sound waves traversed the planet. These pressure waves were detectable for days, with some instruments recording their passage up to seven times, indicating the waves circled the globe multiple times. This systematic recording provided concrete evidence of the eruption’s immense atmospheric impact.
The pressure changes were so forceful that they caused physical effects distinct from the direct volcanic explosion. The eruption generated infrasound, which consists of very low-frequency waves inaudible to humans but capable of causing physical sensations or vibrations. These air pressure changes contributed to the destruction of buildings and structures in areas far beyond the immediate blast zone.