Krakatoa Eruption

The Krakatoa eruption of 1883 stands as one of the most powerful and catastrophic volcanic events in recorded history. Located in the Sunda Strait between the islands of Java and Sumatra in Indonesia, Krakatoa (Indonesian: Krakatau) was a small volcanic island that exploded with extraordinary force, leading to the destruction of most of the island, massive tsunamis, and significant global climatic effects. The event is notable not only for its scale but also for its profound geological, environmental, and human consequences.

Geological Background

Krakatoa lies along the Sunda Arc, a volcanic chain formed by the subduction of the Indo-Australian Plate beneath the Eurasian Plate. This region, part of the Pacific “Ring of Fire”, is known for intense seismic and volcanic activity. Krakatoa itself was part of a volcanic group comprising several small islands, including Lang Island, Verlaten Island, and Rakata.
Prior to 1883, Krakatoa had erupted several times, most notably in 1680. The 1883 eruption was preceded by months of increased seismic activity, small eruptions, and explosions, which culminated in the cataclysmic series of events in late August of that year.

The 1883 Eruption Sequence

The eruption began with minor activity in May 1883, when ash plumes rose several kilometres into the atmosphere. Over the next few months, the explosions became increasingly violent. The climax occurred between 26 and 27 August 1883, when four enormous explosions took place, the largest at approximately 10:02 a.m. on 27 August.
The force of the final explosions was immense, estimated to have released the energy equivalent of over 200 megatons of TNT—roughly 13,000 times greater than the atomic bomb dropped on Hiroshima. The explosion was heard as far as 4,800 kilometres away, in places such as Perth, Australia, and Rodrigues Island near Mauritius. It remains the loudest sound ever recorded in human history.
The eruption destroyed most of the island of Krakatoa, leaving only remnants of Rakata and the smaller surrounding islets. The volcanic column reached heights of up to 50 kilometres, ejecting over 20 cubic kilometres of rock, ash, and pumice into the atmosphere.

Tsunamis and Immediate Impact

The most devastating aspect of the eruption was the series of tsunamis triggered by the collapse of the volcanic island into the sea. Waves over 30 metres high swept across coastal regions of Java and Sumatra, obliterating hundreds of towns and villages.
An estimated 36,000 to 40,000 people were killed, though some reports suggest higher figures. The towns of Anjer (Anyer) and Teluk Betung were completely destroyed. Coastal settlements up to 40 kilometres inland were inundated by waves that carried coral blocks, trees, and boats far from the shoreline.
The ash and pumice fall also caused widespread darkness, with sunlight blocked for several days. Ships hundreds of kilometres away reported thick layers of ash on their decks and difficulties navigating through pumice rafts floating on the sea.

Atmospheric and Climatic Effects

The eruption had remarkable global atmospheric consequences. The enormous quantities of ash and sulphur dioxide injected into the stratosphere spread worldwide, forming a high-altitude haze that reflected sunlight and led to a temporary global temperature drop of around 1.2°C in the following years.
Spectacular sunsets and optical phenomena were observed around the world for months. The famous painter Edvard Munch is believed to have been inspired by such red skies when he created The Scream. Atmospheric phenomena recorded in Europe and North America included vivid red and orange twilights, known as “volcanic sunsets”, as well as unusual optical effects like Bishop’s Ring, a halo around the Sun caused by volcanic aerosols.
Scientific observations following the eruption also contributed to the early study of atmospheric circulation and climate dynamics, marking one of the first instances where a natural disaster was linked to global climatic change.

Geological Consequences and Formation of Anak Krakatau

The 1883 eruption destroyed approximately two-thirds of Krakatoa Island. The remaining caldera, about 7 kilometres in diameter, lay partly submerged beneath the sea. Decades later, new volcanic activity began to form a smaller island in the same location.
In 1927, eruptions built up a new volcanic cone named Anak Krakatau (“Child of Krakatoa”). This young volcano has been continuously active since its formation, frequently erupting and growing in size through successive lava flows and explosive events.
Anak Krakatau continues to be closely monitored due to its potential hazard. In December 2018, part of the volcano collapsed, generating a tsunami that struck coastal areas of the Sunda Strait once again, resulting in significant casualties and property damage.

Scientific Observations and Legacy

The Krakatoa eruption of 1883 occurred during an era of expanding global communication and scientific interest, making it one of the first well-documented natural disasters. Reports were transmitted worldwide via telegraph, and scientific expeditions soon followed.
The Royal Society of London published a detailed report in 1888, based on eyewitness accounts, barometric data, and atmospheric studies. The eruption’s acoustic waves circled the globe multiple times, as recorded by barometers worldwide. These data provided valuable insights into the propagation of sound and pressure waves through the atmosphere.
The eruption also contributed to advances in volcanology and geophysics, highlighting the relationship between volcanic eruptions, tsunami formation, and atmospheric phenomena. It underscored the destructive potential of volcanic island systems and the importance of international monitoring of active volcanoes.

Human and Cultural Impact

Beyond its scientific significance, the Krakatoa eruption profoundly influenced human understanding of nature’s power. Survivors’ accounts described a scene of apocalyptic devastation—entire coastlines erased, the sea filled with debris, and skies darkened for days. The disaster entered global consciousness as a symbol of natural catastrophe and was widely reported in newspapers, literature, and art.
In Indonesia, the event remains deeply embedded in cultural memory. Local legends and oral histories recount the eruption as divine retribution or as a marker of great change. For the wider world, Krakatoa became synonymous with both awe and destruction, illustrating the fragile balance between human civilisation and the forces of nature.

Modern Significance

Today, Krakatoa and its successor, Anak Krakatau, are closely observed by the Indonesian Centre for Volcanology and Geological Hazard Mitigation (CVGHM) and international scientific organisations. The region remains a vital site for studying volcanic island arcs, caldera formation, and eruption dynamics.
Modern technology, including satellite monitoring and seismic networks, has greatly improved understanding of volcanic processes, allowing for earlier warnings and better disaster preparedness. Nevertheless, the ongoing activity at Anak Krakatau serves as a reminder of the region’s volatility.