1883 Krakatoa Eruption
One of the best attested major eruptions of modern times occurred on Krakatoa Island, in the Sunda Strait between Java and Sumatra in the then Dutch East Indies (today’s Indonesia). Krakatoa, which had three linked volcanic peaks, began erupting on the afternoon of August 26, 1883 and peaked the following morning. By the time it stopped, most of Krakatoa Island and its surrounding archipelago had disappeared, collapsing into a caldera. Minor seismic activity continued for months afterward, before the volcano finally fell silent.
While the intensity and suddenness of the eruption were surprising, the eruption itself was not, for there had been plenty of warnings. For years, there had been intense seismic activity on Krakatoa, with earthquakes felt as far away as Australia. Three months before the dramatic explosion, beginning in May, the volcano started to vent steam and spew columns of ash up to 20,000 feet into the air, and give off explosions that were heard in Jakarta, 100 miles away.
That went on for a week, then quieted, before resuming again in mid-June, with a thick black cloud that covered the area for a week as the volcano erupted periodically, emitting ash and throwing up pumice that landed hundreds of miles away into the Indian Ocean.
That activity, in turn, increased tidal activity, with the results that ships had to be moored with strong chains to resist the tide’s suddenly strong ebb and flow. By early August, a desolate and abandoned Krakatoa was covered by nearly two feet of ash, and all vegetation had died, leaving only tree stumps.
The final act started early in the afternoon of August 26. By 2 PM, explosions could be heard every 10 minutes or so, and Krakatoa had spewed a 20-mile high ash cloud that was visible from far off, and ships up to 12 miles away reported a heavy ash fall, accompanied by bits of pumice up to 4 inches wide. By early evening, the seismic activity had given rise to mini tsunamis, which struck the Sumatran and Javan coasts 25 miles away.
The climax began early the following morning, with two big eruptions, at 5:30 and 6:44 AM on August 27th, which gave rise to tsunamis. That was followed at 10:02 AM by the loudest sound ever heard until then in recorded history: a cataclysmic explosion of about 180 decibels, that was equivalent to 15,000 Hiroshima bombs and that put the preceding eruptions to shame. It was heard nearly 2000 miles away in Perth, Australia, 3000 miles away on the island of Rodrigues, near Mauritius in the Indian Ocean, and produced a tsunami about 100 feet high in places.
Yet that was not the worst that Krakatoa had to offer. A fourth, and even more powerful eruption, occurred at 10:41 AM, nearly twice as loud as the previous one, at 310 decibels: so loud that it ruptured eardrums 40 miles away, and was clearly heard from 3100 miles away. A tsunami with a wall of water up to 120 feet high raced out, as ash was flung 50 miles up into the sky by an explosion that produced a pressure wave that was recorded in barometers all over the world.
Recorded on global barometers not once, but seven times, as the pressure wave raced around the planet for five days, circling the globe and coming back to the volcano, and continuing on, again and again, and again, still powerful enough to register on barometers everywhere on earth as circled the planet multiple times. The catastrophic eruptions and resultant tsunamis killed at least 36,000 according to official Dutch estimates, but modern estimates put the true casualty figures at up to 120,000.