Krakatoa Eruption of 1883: The Volcano Heard Across the World

The eruption of Krakatoa in August 1883 was one of the deadliest and most violent volcanic events in recorded history. The volcanic island, in the Sunda Strait between Java and Sumatra in what was then the Dutch East Indies, blew itself apart on 26–27 August 1883. Tsunamis killed tens of thousands of people, and the ash and gas it released affected skies and weather across the whole planet.

Background

Krakatoa (Krakatau in Indonesian) was a small group of islands lying in the Sunda Strait, a busy shipping lane linking the Java Sea with the Indian Ocean. The main island was made up of several volcanic cones, the highest of which was Rakata. The volcano had last erupted in about 1680 and was generally thought to be dormant.

The region sits above a subduction zone, where the Indo-Australian tectonic plate slides beneath the Eurasian plate. This process feeds magma to the long chain of Indonesian volcanoes. Coastal Java and Sumatra were home to many towns and villages, and the Dutch colonial administration ran lighthouses, ports and telegraph stations along the strait.

What happened

Krakatoa came back to life on 20 May 1883, when steam and ash began to rise from the island and explosions were heard as far away as Batavia (now Jakarta), about 160 kilometres to the east. Activity continued on and off through June and July, and sightseers even visited the island by boat. The first activity came from Perboewatan, the northernmost cone, but by August several vents were erupting. Because the early eruptions were moderate, there was little alarm, and no one at the time had the scientific means to predict what would follow.

The climactic phase began on the afternoon of 26 August 1883, with a series of increasingly powerful explosions and a tall column of ash. On the morning of 27 August came four enormous explosions. The largest, shortly after 10 a.m. local time, was heard on Rodrigues Island near Mauritius, almost 4,800 kilometres away. It is often called the loudest sound in recorded history.

As the magma chamber emptied, roughly two-thirds of the island collapsed into the sea, leaving a submarine caldera, a large basin-shaped crater. The eruption is ranked 6 on the Volcanic Explosivity Index, a scale that measures the size of eruptions. Fast-moving flows of hot ash and gas, known as pyroclastic flows, travelled across the sea and struck parts of southern Sumatra.

Darkness fell over the strait as ash rained down, and ships many kilometres away reported pumice, falling ash and violent waves. By the morning of 28 August the explosions had died down. Where most of the island had stood, the sea was now more than 200 metres deep in places, and only part of the Rakata cone remained above water.

By the numbers

The tsunamis

The most destructive effect of the eruption was a series of tsunamis. Waves reported to be more than 30 metres high in places swept over the low-lying coasts of western Java and southern Sumatra. Towns such as Anjer (Anyer) and Merak on Java and Telok Betong (now part of Bandar Lampung) on Sumatra were largely destroyed.

The official Dutch death toll was 36,417, and some historians think the real figure was higher. Most victims drowned in the waves. At Telok Betong, a government steamship, the Berouw, was carried well inland by the water. Smaller sea-level changes were recorded by tide gauges as far away as South Africa and the English Channel, though historians and scientists debate how much of this was caused directly by the waves.

There was no warning system, and the waves arrived within minutes to an hour or two of the largest explosions, depending on the distance. Coastal villages of fishermen and farmers, built close to the shore, suffered the worst. Most of the dead were local Javanese and Sumatran people, along with smaller numbers of European and Chinese residents and colonial officials. Lighthouses, piers, plantations and rice fields along both sides of the strait were swept away, and bodies and debris were found floating in the strait for weeks.

Floating rafts of pumice blocked harbours and drifted far out into the Indian Ocean. Some were reported reaching the coast of East Africa many months later.

Global effects

The eruption’s pressure wave was recorded by barometers around the world, circling the globe several times. Nothing comparable was measured again until the Hunga Tonga eruption of 2022, whose atmospheric wave was also detected travelling around the Earth several times. Ash and sulphur gases were thrown high into the stratosphere, where they spread around the Earth within weeks.

For months afterwards, people in many countries saw vivid red and orange sunsets, and the Moon and Sun sometimes appeared blue or green. In some places the glow was so bright that fire brigades were called out, believing there was a large fire. Average global temperatures fell slightly over the following year or so, before returning to normal as the haze cleared.

These optical effects were described by scientists, newspapers and artists. The English painter William Ascroft made hundreds of sketches of the coloured skies seen over London in late 1883, and some of them were reproduced in the Royal Society’s report.

Myths and facts

Myth: Krakatoa was the biggest eruption in history. It was enormous, but the eruption of Mount Tambora in 1815, also in present-day Indonesia, was considerably larger (VEI 7) and caused far more deaths. Krakatoa is better known partly because it happened in the age of the telegraph and modern science.

Myth: most victims died in the explosion. The great majority drowned in the tsunamis. Pyroclastic flows did kill people on the Sumatran coast, but they were responsible for only a small share of the deaths.

Myth: Krakatoa is east of Java. The 1960s Hollywood film Krakatoa, East of Java spread this error. The volcano lies west of Java, in the Sunda Strait.

Disputed: the link with The Scream. Some researchers have suggested that the blood-red sky in Edvard Munch’s painting The Scream (1893) recalls the Krakatoa sunsets seen in Norway. This is possible but unproven, and art historians have offered other explanations.

Investigation and aftermath

The Dutch mining engineer and geologist Rogier Verbeek studied the eruption and published a major report in the mid-1880s. He visited the ruined islands, mapped the new shape of the seabed, collected eyewitness accounts and timed the explosions using records such as the pressure gauge at the Batavia gasworks. His work remains a basic source on the eruption. In Britain, the Royal Society set up a committee to gather reports of the eruption’s effects from around the world. Its findings were published in 1888 as The Eruption of Krakatoa and Subsequent Phenomena, one of the first large-scale studies of a natural disaster with global reach.

Because news travelled quickly by submarine telegraph cable, Krakatoa was also one of the first natural disasters to be reported around the world within hours. Newspapers in Europe and North America carried accounts of the catastrophe soon after it happened.

The remains of the island were left buried under hot ash and completely without life. They became a natural laboratory for biologists. When the Dutch botanist Melchior Treub visited in 1886, he found that ferns and blue-green algae had already begun to colonise the ash, and over the following decades plants, insects, birds and reptiles returned. Studies of this recovery became a classic case in ecology.

In 1927 a new volcano broke the surface of the caldera and was named Anak Krakatau, “Child of Krakatoa”. It grew through frequent eruptions to a height of more than 300 metres before part of it collapsed into the sea on 22 December 2018, causing a tsunami that struck the coasts of Java and Sumatra without warning. The Krakatau islands are now a nature reserve within the Ujung Kulon National Park World Heritage Site.

Timeline

• c. 1680: Krakatoa’s previous known eruption.
• 1883, 20 May: The volcano reawakens, with explosions and ash clouds.
• 1883, 26 August: The climactic phase begins in the afternoon.
• 1883, 27 August: Four huge explosions; the island collapses and tsunamis strike Java and Sumatra.
• 1888: The Royal Society publishes its report on the eruption and its worldwide effects.
• 1927: Anak Krakatau (“Child of Krakatoa”) rises from the sea inside the caldera.
• 2018, 22 December: A flank collapse of Anak Krakatau causes a deadly tsunami in the Sunda Strait.

Why it matters

Krakatoa showed how a single volcano could affect the entire planet, from tsunamis on nearby coasts to coloured skies and cooler weather thousands of kilometres away. The scientific studies that followed helped lay the foundations of modern volcanology and the study of how eruptions influence climate. Like the eruption of Vesuvius in AD 79, it remains a defining example of the danger of living near an active volcano, a lesson renewed by Anak Krakatau’s 2018 collapse.