Krakatoa history: 36,417 deaths and a sound heard worldwide

Krakatoa history is written in ash, water, and sound. The 1883 eruption tore through the island on 27 August, and its effects raced far beyond the Sunda Strait.

The eruption that began in May

The eruption began on 19 May 1883 and lasted more than five months. In its first phase, ash eruptions reached an estimated altitude of 6 kilometres. By late June, a thick black cloud covered the islands for five days.

On 26 August 1883, a black ash cloud could be seen 27 kilometres high. The main eruption came the next day, with an estimated volcanic explosivity index of six. It destroyed over 70 percent of the island and its surrounding archipelago.

The day the loudest sound was heard

The third explosion of the day, at 10:02 in the morning, remains the loudest-known sound in history. It was heard 3,110 kilometres away in Perth and 4,800 kilometres away on Rodrigues near Mauritius.

The acoustic pressure wave circled the globe more than three times. That single blast became part of Krakatoa history not only for its force, but for how far its sound traveled across oceans and continents.

Tsunamis that crossed the sea

The eruption and the tsunamis it created were attributed at least 36,417 deaths. Some of the worst tsunamis were estimated to have been over 30 metres high in places. The town of Merak was destroyed by a tsunami that was 46 metres high.

Ash and water worked together in the devastation. The eruption propelled ash to an estimated height of 80 kilometres, while the waves reshaped coastlines and wrecked settlements around the strait.

Global skies after Krakatoa

The eruption caused a volcanic winter and lowered average Northern Hemisphere summer temperatures by 0.4 degrees Celsius in the following year. It also darkened the sky worldwide for years afterward and produced spectacular sunsets worldwide for many months.

For a long stretch after the blast, the sky carried unusual signs of the event: a Bishop's Ring around the sun by day and a volcanic purple light at twilight. Those effects made the eruption visible in memory far beyond the islands themselves.

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