A volcanically-induced tsunami

Krakatau was a small volcanic island located in the Sunda Strait between Java and Sumatra. Its activity has been chronicled by Simpkin and Fiske (1983). The volcano began erupting in May, 1883, with small ash clouds and rumblings. Although the modern scientific approach to the study of volcanoes has exonerated the gods Pluto and Vulcan from blame, the belief in myths and gods still tends to be directly proportional to the proximity of the person to the eruption -- certainly those who were close to Krakatau when it roared into vigorous action at about 1:00 p.m. on 26 August. This event produced an eruption column 30 kilometers high, and by 5:00 p.m. the first of several giant sea waves (tsunamis), hit the coasts of Java and Sumatra. The noise of explosions was described as deafening 40 kilometers from the volcano, but these explosions were only a prelude to the main eruptions. The following day, at 10:02 a.m., most of the island disappeared in a giant cataclysm that produced an ash column that rose to a height of 80 kilometers. At about the same time that the island disappeared, gigantic tsunamis rushed toward the Java and Sumatra coasts. Several coastal villages were completely destroyed as the giant waves rushed onto land as far up as 240 meters above sea level. There were nine gigantic waves in all and 36,000 people perished because of them.

It was originally thought that Krakatau beheaded itself in the explosion, but pieces of the volcano that should have been abundantly distributed in the area surrounding the volcano, were absent, leading to the conclusion that so much pyroclastic material had emptied into the atmosphere, that it created an empty chamber beneath the volcano. Removal of support caused the volcano to collapse into the hole. Recently, evidence has shown that the tsunamis were created by displacement of sea water from the fall back of pyroclastic material from the lower part of the towering eruption column (Sigurdsson et al., 1991). Because Krakatau is an island, the enormous volume of material from the collapsing eruption column entered the sea and displaced enough water to generate the killer waves.


Sigurdsson, H., Carey, S. and Mandeville, C., 1991. Krakatau. National Geographic Research, 7:310-327.

Simkin, T. and Fiske, R.S., 1983. Krakatau 1883: the volcanic eruption and its effects. Smithsonian Institution, Washington, D.C., 464 pp.