The volcanic island of Krakatoa, also spelled Krakatao or Krakatowa, is best known for the huge volcanic eruptions that took place there on Sunday, 26 August 1883. In a sequence of massive explosions over the morning and the beginning of the afternoon, the 2,625 feet (800m) high peak erupted and spewed forth a torrent of volcanic magma into the Sundra Strait in the Indian Ocean. About 2.9 cubic miles (12cu km) of magma were released and the initial blast coupled with the tsunamis occasioned by magma falling into the sea meant that the death-toll reached close to 40,000 people. The three islands that constituted Krakatoa were mostly destroyed by the blast.
The island of Krakatoa was situated between the then Dutch colonies of Java and Sumatra in the Sundra Strait. Before its eruption and eventual self-destruction, Krakatoa sat 492 yards (450 m) above sea level and measured 8.8 square miles (23 sq km). It is believed by scientists that prior to the fateful Sunday afternoon in 1833, the island had shown signs of what is known as plinian volcanic activity. This plinian activity (named after Pliny the Younger, chronicler of the eruption of Vesuvius in 79 AD) is thought to have involved the expulsion of large quantities of matter into the atmosphere. This is evidenced by the reports of sailors who traveled along the straits in the months before the eruption and witnessed a great plume of smoke issuing from Krakatau’s crater along with pumiceous bars and ash dispersed along the strait.
The activity that presaged the cataclysmic blast of a few months later was from the Perboewetan volcano of the Krakatoa complex of volcanoes. The potential for a massive eruption was increased by this earlier activity because it widened the caldera beneath the islands of Krakatoa which added to the build-up of pressure. At around 5:30 a.m. and then at about 7:00 a.m. on the day of the fatal eruption, the island experienced two huge explosions that caused tsunamis to wreak havoc in the Sundra Strait. Then, around three hours later, at 10:00 a.m., the island exploded and destroyed itself in one huge cataclysmic explosion. What had previously been 8.8 square miles (23 sq km) of spewing volcano imploded into the 3.7 mile (6km) caldera on which it stood.
The explosion was the loudest sound ever reported and was equivalent to approximately 200 megatons of trinitrotoluene (TNT). The sonic blast of the explosion reached as far as Australia and was also reported in Sri Lanka and the Philippines.