Krakatoa: The Loudest Sound Ever Recorded
Now, Krakatoa is far from the loudest, biggest, deadliest, or most world altering explosion to ever happen, even in the brief period of human existence. But in the time that humanity has been able to measure and record such explosions, Krakatoa has never been equaled.
Situated in Indonesia, a nation notorious for its volcanic activity, Krakatoa first caught the world's attention in May of 1883 as rumblings echoed from deep within the island. Soon after, towering ash clouds began to rise, signaling that the volcano had stirred from its slumber. Over the following two months, the eruption became a spectacle. For European colonists, it was an attraction; for locals, a reason to celebrate; and for scientists worldwide, a rare opportunity to witness a force of nature in action.
On the morning of August 27, 1883, the island erupted in a series of four tremendous explosions, beginning at 6am on the northern side of Krakatoa. The first blast triggered a landslide and a minor tsunami. It’s believed that this landslide allowed sea water and atmospheric gases to mix with the magma, intensifying the pressure inside the caldera. Just hours later, its final, most deafening explosion would become the moment when Krakatoa would stand alone.
Volcanic Explosivity Index
To understand just how massive Krakatoa’s eruption was, we need to understand the Volcanic Explosivity Index (VEI). In layman’s term, it’s basically the volcano version of the Richter scale.
On a scale form 0-8, it measures the amount of debris a volcano hurls into the air in cubic kilometers (km³), with each level increasing by a factor of 10.
VEI 0 = When a volcano releases lava without actually exploding
VEI 1 = 0.0001 km³
VEI 2 = 0.001 km³
VEI 3 = 0.01 km³
VEI 4 = 0.1 km³
VEI 5 = 1 km³ <— Mount St. Helens (May 18, 1980)
VEI 6 = 10 km³ <— Krakatoa (August 27, 1883)
VEI 7 = 100 km³ <— Mt. Tambora (April 10, 1815)
VEI 8 = 1,000 km³ <— Supervolcano (Toba, 75,000 years ago; Yellowstone)
To put it into perspective, Mount St. Helens erupted with almost exactly 1 km³ of tephra, barely qualifying it as a VEI 5. While the two eruptions are only a level apart on the scale, the difference in their scale is staggering. If Mount St. Helens was like a car backfiring, then Krakatoa was like an entire city block exploding. Despite their similar classification, the sheer scale of Krakatoa dwarfs that of St. Helens, making the comparison almost meaningless—it was in an entirely different category.
The Big Bang
On the morning of August 27, 1883, the eruption of Krakatoa unleashed a cataclysmic force exceeding 200 megatons—four times the power of the Tsar Bomba, the most potent nuclear weapon ever tested, and more than 10,000 times the force of the Hiroshima bomb. Over 45 km³ of tephra were hurled 50 miles into the sky, while pyroclastic flows surged at speeds exceeding 100 mph. The eruption's violent force caused nearly 10 square miles of the island to collapse into the sea, displacing an enormous amount of water. This triggered massive tsunamis with waves soaring over 130 feet, their impact reaching as far as Hawaii—7,000 miles away—spreading devastation across vast distances.
While such figures are typical for massive volcanic eruptions, it is Krakatoa’s sheer sonic power that truly sets it apart.
The explosion generated a pressure wave that spread outward at 675 mph, with an estimated sound level reaching a staggering 310 decibels—loud enough to be heard over 3,000 miles away. Anyone within 10 miles of the eruption would have been instantly rendered deaf, while sailors 40 miles from the blast suffered ruptured eardrums. A weather station located 100 miles away recorded a sound level of 180 decibels, comparable to standing beside a rocket launch. As far as 2,000 miles away in Australia, the reverberations were so intense that people mistook the booming cracks for distant gunfire.
In the late 1800's, before the days of fancy satellites, countries around the world relied on barometers to measure air pressure and predict weather. However, since sound can cause changes in air pressure, the Krakatoa eruption was logged all over the world, even after it dropped below the level of human hearing. Weather stations in Australia, Berlin, Paris, and even New York recorded pressure spikes every 34 hours over the next 5 days. This meant that the shockwave from Krakatoa had circled the Earth 3.5 times before it eventually dissipated, earning it the name “The Great Air Wave.”
When all was said and done, less than 30% of the island remained. Krakatoa truly went out with the biggest bang ever.
