When this Indonesian volcanic island exploded in August 1883, it blew the island apart and caused a tidal wave that killed more than 36,000 people. What was it?

The catastrophic volcanic event described refers to the 1883 (Review) eruption of Krakatoa, an Indonesian island volcano situated in the Sunda Strait between Java and Sumatra. On August 27, 1883, Krakatoa experienced a series of massive explosions, culminating in one of the deadliest and most powerful volcanic events in recorded history. These explosions obliterated over 70 percent of the island, collapsing it into a caldera.

The most devastating consequence of the eruption was the generation of colossal tsunamis. Waves, some reaching heights of up to 40 meters (130 feet), ravaged the coastal regions of Java and Sumatra. These immense tidal waves were responsible for the vast majority of the more than 36,000 fatalities officially recorded, though some modern estimates suggest the death toll could have been significantly higher. The sound of the climactic explosion was so immense that it was heard over 4,800 kilometers (3,000 miles) away in places like Rodrigues near Mauritius and Perth, Western Australia, and the atmospheric pressure wave circled the globe multiple times.

Beyond the immediate devastation, the eruption had far-reaching global effects. It ejected an estimated 25 cubic kilometers (6 cubic miles) of rock and ash into the atmosphere, leading to a "volcanic winter" that cooled global temperatures for the following year. The fine dust also produced spectacular and vibrant sunsets around the world for several months. Decades later, a new volcanic island, Anak Krakatau, meaning "Child of Krakatoa," emerged from the caldera left by the 1883 eruption, continuing the volcanic activity in the region.