One hundred thirty years ago today – Krakatoa

The gigantic eruption that made the volcanic island of Krakatau in Indonesia (or commonly in English, Krakatoa) famous down to the present day actually began on August 26th, 1883.  But the final eruption that destroyed most of the island happened on the following day, in a series of four gigantic explosions.  Ultimately the volcano was blamed for more than 36,000 deaths, although some historians and scientists consider that number (estimated by the Dutch authorities, as it was part of the Dutch East Indies at that time) to be much too low.  Krakatoa was the first major volcanic eruption to be studied and measured with modern scientific instruments such as seismographs and barographs.

The effects of the eruption were many, and impressive.  Measured as a 6 on the VEI scale, the volcano is believed to have put more than ten cubic kilometers of material into the atmosphere.  The ash cloud eventually reached a height of 50 miles.  The third explosion on August 27th is believed to have been the loudest explosion in recorded human history.  People recorded hearing the blast in Perth in Western Australia and on the islands of Mauritius, east of Madagascar – 1,900 and 3,100 miles away, respectively.

Tsunamis caused by the eruption (probably from pyroclastic flows hitting the sea) rose to a height of 130 feet or more in some places.  The town of Merak, some 50 miles northeast of the volcano and some 35 miles west of Jakarta, was virtually wiped out.   For months, even years afterward, ships would report encountering floating islands of pumice and ash far out to sea.  The following year, the average world temperature dropped by over 1.2 degrees and lower average temperatures continued for several more years.

And you want to know what’s really scary? Relatively speaking, Krakatoa isn’t even the worst that has happened.

Like I said, Krakatoa was only a 6 on the VEI scale.  Tambora (also in what is now Indonesia) in 1815 was a 7.  That volcano caused the following year to become known as the year without a summer here in New England.  And there are eruptions that have occurred in the (for humans) distant past that are believed to have reached an 8, including the Toba eruption about 70,000 years ago.  That event is often associated with a human genetic bottleneck at around the same time.


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