Feel the aftershocks of Krakatoa eruption
WHAT caused ships anchored off Port Elizabeth to strain at their moorings and the needle of the port’s prized mechanical tide-gauge to jump on August 28, 1883? Four hours later an even larger surge was measured, 1.4m above the norm, and more strange oscillations were recorded the following day.
The swells originated 7 546km to the north-east and had taken about 13 hours to reach the city. They were triggered by a series of eruptions that had been brewing deep below the crater of Krakatoa, a volcanic island in the Sunda Strait between Java and Sumatra, now Indonesia.
At the time of the catastrophe the islands were Dutch colonial possessions administered from Batavia. Volcanology was in its infancy and no one appreciated the danger that Krakatoa posed because it had been dormant since 1680.
It awoke from its slumber in May 1883 with a series of tremors, rumbles and eruptions of steam, smoke and pumice which frightened the people of the nearest village (Ketimbang on Sumatra) and unsettled Johanna Beyerinck, wife of the Dutch controller.
The warning signs tailed off and nothing alarming happened for the next three months, but subterranean pressures were rising inexorably and continued to build until something had to give.
The plug that blocked the pipe below the crater blasted out on August 26, unleashing 21 hours of terror and destruction on the inhabitants of hundreds of villages in the vicinity. The sky darkened as tons of volcanic matter, ash and dust roared into the heavens and the shallow seas slopped back and forth like water in a bathtub.
At first, (Willem) Beyerinck refused to flee to higher ground, but changed his mind when the first moderate-sized tsunami hit Ketimbang. He urged his family, servants and villagers to climb through the hellish night to reach a holiday cottage in the mountains, but even there they didn’t feel safe.
At dawn the next day, the volcano began a four-hour orgy of self-destruction. Three devastating eruptions followed, and then at 10am Krakatoa exploded in a terrifying, eardrum-shattering roar that was said to be the loudest detonation ever recorded. It was clearly heard in Perth, Australia, 3 000km away.
A 35m tsunami crashed ashore within 30 minutes, but this was outpaced by a super-heated pyroclastic flow containing gas, ash and rock travelling at immense speed. It hit the Beyerincks’ shuttered cottage and began to roast them alive. The parents and two children survived, despite serious burns, but their baby and half the villagers sheltering nearby died.
The explosion thrust huge quantities of dust into the atmosphere which lowered temperatures and caused brilliant orange sunsets and after-glows across the world. Water was the big killer, however: It destroyed 165 coastal villages and killed most of the estimated 36 400 casualties.