Krakatoa: The Loudest Sound in History - Eruptions, Tsunamis & Anak Krakatau

Krakatoa (or Krakatau in Indonesian) is more than just a volcano; it is a name synonymous with destruction on a planetary scale. Located in the Sunda Strait between the massive islands of Java and Sumatra, this volcanic island system is famous for its 1883 eruption—one of the deadliest and most violent volcanic events in recorded human history.

The 1883 eruption didn’t just obliterate the island; it produced the loudest sound ever heard by modern humans, triggered tsunamis that killed tens of thousands, and altered the global climate for years. Today, the legacy of that disaster lives on in Anak Krakatau (“Child of Krakatoa”), a new, highly active volcano that rose from the drowned caldera of its “parent” and continues to pose a deadly threat to the region.

Geological Setting: The Fire in the Strait

The Sunda Arc

Krakatoa sits atop a subduction zone where the Indo-Australian Plate moves northward and slides beneath the Eurasian Plate. This tectonic collision creates the Sunda Arc, a chain of active volcanoes responsible for some of the most powerful eruptions on Earth, including Tambora (1815) and Toba (74,000 years ago).

A History of Destruction

Before 1883, Krakatoa wasn’t a single peak but a group of three linked volcanic cones on a single island: Rakata, Danan, and Perboewatan. Historical records suggest a massive ancient eruption occurred around 416 AD (or 535 AD), leading to a caldera collapse that separated Sumatra and Java. The 19th-century island was essentially a “lid” on a boiling pressure cooker of silica-rich magma waiting to blow.

The 1883 Cataclysm: The Day the World Exploded

The eruption of 1883 wasn’t a sudden event but a terrifying crescendo that lasted for months.

The Awakening (May–June 1883)

Activity began on May 20, 1883, with the Perboewatan cone roaring back to life. Ash clouds rose 6 km into the skies, and explosions could be heard in Batavia (modern-day Jakarta), 160 km away. Activity fluctuated for months, drawing sightseers who chartered boats to watch the “fireworks,” unaware they were witnessing the fuse burning down on a megaton bomb.

The Climax (August 26–27, 1883)

On August 26, the activity intensified significantly. By 2:00 PM, a black cloud of ash covered the region, turning day into night.

The climax arrived the next morning, August 27, in a series of four gargantuan explosions:

1. 5:30 AM: A massive explosion at the Perboewatan vent.
2. 6:44 AM: A second explosion at the Danan vent.
3. 10:02 AM: The “Great Explosion.” This was the big one.
4. 10:41 AM: A final blast disrupting the remaining slopes of Rakata.

The Loudest Sound in History

The 10:02 AM explosion is widely considered the loudest sound ever recorded in modern history.

• It was heard clearly in Alice Springs, Australia (3,600 km away) and on the island of Rodrigues near Mauritius (4,800 km away).
• People 500 km away thought it was cannon fire from a nearby ship.
• Barometers all over the world went crazy. The shockwave (a pressure wave in the atmosphere) circled the globe seven times. It was still detectable by instruments five days later.
• Anyone within 16 km would have gone instantly deaf. The sound energy was estimated at roughly 310 decibels—far beyond the threshold of human pain and fatal acoustic trauma.

The Killer Tsunamis

While the explosion was terrifying, the water was the true killer. The collapse of the island into the empty magma chamber displaced cubic kilometers of seawater, generating tsunamis up to 42 meters (135 feet) high.

• The waves devastated the coastal towns of Java and Sumatra, including Anjer and Merak.
• The steamships Berouw was carried 3 km inland and deposited in a jungle valley.
• 36,417 people were officially recorded as dead, though modern estimates suggest the toll could have been over 120,000. Most died from the tsunamis, not the eruption itself.

Pyroclastic Flows on Water

One of the most terrifying phenomena observed was pyroclastic flows (avalanches of hot gas and ash) traveling over the surface of the ocean for up to 40 km. A cushion of steam generated by the hot ash boiling the seawater allowed these deadly currents to “hover” across the Sunda Strait, burning victims in Sumatra who thought they were safe across the water.

Global Aftermath: A World Changed

The eruption ejected approximately 25 cubic kilometers of rock, ash, and pumice. The finer particles reached the stratosphere and spread around the planet.

The Year of No Sun

The volcanic dust and sulfur dioxide aerosols acted like a global solar shield, reflecting sunlight. Global average temperatures dropped by about 1.2°C (2.2°F). Weather patterns were disrupted worldwide for five years.

Spectacular Sunsets and Art

The atmospheric dust scattered sunlight, creating incredibly vivid, fiery red and orange sunsets for years.

• Fire trucks were called out in New York and London because people thought the sky was on fire.
• Edvard Munch’s “The Scream”: Many art historians believe the blood-red sky depicted in Munch’s famous painting was inspired by the vivid twilight skies he witnessed in Norway after the Krakatoa eruption.

Anak Krakatau: The Child is Born

After the 1883 eruption, Krakatoa was gone. Only a fragment of Rakata Island remained. The sea swallowed the rest. But the volcano was not dead.

In 1927, submarine eruptions breached the surface. A new island formed, disappeared, and formed again. By 1930, it established itself permanently and was named Anak Krakatau (“Child of Krakatoa”).

A Fast-Growing Giant

For nearly a century, Anak Krakatau has been one of the fastest-growing volcanoes on earth, growing at an average rate of 5 meters (16 feet) per year. It built a classic cone shape, emitting frequent Strombolian bursts of lava and ash, becoming a popular (if dangerous) tourist attraction.

The 2018 Collapse and Tsunami

On December 22, 2018, history repeated itself on a smaller scale. A massive section of Anak Krakatau’s southwest flank—destabilized by decades of rapid growth—collapsed into the sea.

• The landslide triggered a silent tsunami that struck the coasts of Java and Sumatra at night, without the warning of an earthquake.
• 437 people died and thousands were injured.
• The volcano lost two-thirds of its height overnight, dropping from 338 meters to just 110 meters. The once-mighty cone was reduced to a flat stump just above the waterline.

Current Status

Since the 2018 collapse, Anak Krakatau has been rebuilding itself rapidly. It has already regained significant height (now around 155 meters) and remains highly active. A circular crater lake formed and was subsequently filled by new lava flows. The “Child” is growing up again, and scientists monitor it closely for stability.

Tourism and Safety

Visiting Krakatoa is an adventure, but it comes with risks.

• Safety Zones: The Indonesian government frequently establishes a “No-Go Zone” extending 2 to 5 km from the crater. Landing on Anak Krakatau itself is currently strictly forbidden due to the risk of sudden explosions and landslides.
• Boat Tours: Tourists can take day trips from Carita Beach or Anyer (West Java) or from Kalianda (Lampung). These tours usually involve a boat ride to the islands of Rakata or Sertung (remnants of the 1883 rim), which offer safe viewpoints and opportunities for snorkeling over untouched coral reefs growing on lava flows.
• The Experience: Seeing the smoking vent of Anak Krakatau surrounded by the ghostly remnants of its parent is a humbling reminder of nature’s power.

Life Finds a Way: The Rakata Experiment

Krakatoa is the world’s greatest study in island biogeography.

• Sterilization: The 1883 eruption killed everything on the remaining islands. It was a biological blank slate.
• Arrivals: Scientists monitored the return of life. First came the spiders (ballooning on the wind), then ferns (spores), then monitor lizards (swimming), and finally birds and fig trees.
• The Lesson: It proved that life is incredibly resilient and mobile. Today, the remnant islands are covered in dense tropical rainforest again, deafening with the sound of cicadas.

Atmospheric Physics: The Bishop’s Ring

The eruption created new science.

• Bishop’s Ring: A halo around the sun observed after the eruption was named after Sereno Bishop, who first described it. It helped scientists discover and understand the stratosphere and the jet streams, which carried the ash around the world faster than anyone thought possible.

Pop Culture Icon

“Krakatoa” has transcended geology to become a cultural meme for “big explosion.”

• Movies: From Krakatoa, East of Java (which notoriously got the geography wrong—it’s west of Java) to mentions in SpongeBob, the name evokes instant recognition.
• Literature: It features in the children’s classic The Twenty-One Balloons, cementing its place in the imagination of generations.

Coral Resilience

Under the sea, another recovery happened.

• Lava Reefs: The lava flows from Anak Krakatau that entered the sea provided a hard substrate.
• Growth: Marine biologists are amazed at how fast table corals and soft corals have colonized these fresh lava rocks. The underwater slopes are now vibrant reefs, teeming with fish, oblivious to the fact that their foundation is an active volcano.

Conclusion

Krakatoa serves as the ultimate case study in volcanic hazard. From the physics of the “loudest sound” to the tragedy of the 2018 tsunami, it highlights the complex relationship between geology and humanity. It taught us that volcanoes don’t just affect their neighbors—they can touch the entire planet through climate change and atmospheric phenomena. As Anak Krakatau continues to grow, it remains a ticking clock in the Sunda Strait, watched nervously by both scientists and the millions living on its shores.

Technical Facts at a Glance

• Location: Sunda Strait, Indonesia
• Coordinates: 6.102°S 105.423°E
• Original Height (pre-1883): ~813 m
• Current Height (Anak Krakatau): ~155 m (Variable)
• Primary Rock Type: Andesite / Dacite
• 1883 VEI: 6 (Colossal)
• 1883 Death Toll: 36,417 (Official)
• Loudest Sound: ~310 dB (1883 Climax)