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.

Located in Indonesia, one of the most volcanically active countries in the world, Krakatoa gained the attention of the world when it began to rumble in May of 1883. Soon after, ash clouds began rising over the island, at which point, everyone knew the volcano had awoken. Over the next 2 months it would become a tourist attraction for European colonist, locals saw the eruption as a cause for celebration, and scientist from around the world came in droves, all of whom were eager to see what would happen next.

Starting at 6am on August 27, 1883, the first of 4 massive explosions rang out on the northern side of the island causing a landslide and a small tsunami. It’s theorized that the landslide allowed sea water and other atmospheric gases to enter the caldera, react with the magma and adding to the pressure within. A few short hours later, Krakatoa would give its final and loudest roar.

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)

For context, Mount St. Helens released almost exactly 1 km³ of tephra, barely qualifying as a VEI 5. But even though the two are only 1 level apart, if Mount St. Helens was like stubbing your toe, then Krakatoa was like stepping on a landmine. As close as they are on the scale, Krakatoa was an event of such greater magnitude, they really can’t be compared. It’s literally on another level.

The Big Bang

At 10am on August 27, 1883, Krakatoa exploded with the force of over 200 megatons; 4 times more powerful than the Tsar Bomba (the most powerful nuclear weapon ever tested), and over 10,000 times that of the Hiroshima bomb. 45 km³ of tephra was thrown over 50 miles into the air, with pyroclastic flows reaching over 100 mph. The force of the eruption caused nearly 10 square miles of the island to collapse into the sea, displacing an immeasurable amount of water and causing tsunamis with waves reaching over 130 feet high, the effects of which were felt as far away as Hawaii, 7,000 miles away.

But while these numbers may be par for the course when it comes to massive volcanos, it’s in the category of sound where Krakatoa stands alone.

The pressure wave radiated out from Krakatoa at 675 mph and is estimated to have reached 310 decibels, loud enough to be heard 3,000 miles away. Anybody within 10 miles would’ve immediately gone deaf. Sailors 40 miles away had their eardrums ruptured. A weather station 100 miles away measured a sound of 180 decibels, the equivalent to standing next to a rocket launch. 2,000 miles away in Australia, the cracks of the explosions were so loud people thought they were hearing nearby gunshots.

In the late 1800's, before the days of fancy satellites, countries around the world used 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 would measure a spike in pressure every 34 hours over the next 5 days. That means the sound wave from Krakatoa circled the Earth 3.5 times before fading away, leading to it being christened “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.