In a few days we will reach the 125th anniversary of the loudest bang in history, which happened when the island of Krakatoa blew itself apart in a series of massive explosions on 26 and 27 August 1883.
Krakatoa lies between Java and Sumatra in Indonesia. Its volcano has erupted repeatedly, massively and with disastrous consequences throughout recorded history, but the best known eruption is that of 1883, which followed a period of dormancy lasting 200 years.
Towards the end of May of that year, booming sounds were heard up to 100 miles away, and a column of ash and steam was seen rising to an estimated 36,000ft. This activity continued to a greater or lesser extent over the following months, until the cataclysmic explosions began on 26 August.
The eruption ejected more than 25 cubic kilometres of rock, ash, and pumice, and generated the loudest sound ever historically reported. It was so loud that emergency services were alerted in communities up to 2,000 miles distant.
A common assumption was that the sounds were from a vessel or vessels in distress, and search parties were dispatched accordingly. One place in which this happened was Diego Garcia, in the Chagos islands, some 2,267 miles from Krakatoa.
Perhaps most remarkably of all, the chief of police in Rodriguez, near Mauritius, almost 3,000 miles away, filed a report that “several times during the night reports were heard coming from the eastward like the distant roar of heavy guns”.
The areas surrounding Krakatoa were plunged into darkness for 24 hours following the eruption, which generated a tsunami with waves over 130 feet in height. The official death toll was 36,417, most of whom were killed by the giant waves, and when the eruption was over only one third of Krakatoa remained above sea level, and new islands of steaming pumice and ash lay to the north.
Every documenting barograph in the world recorded the passage of the airwave, which reverberated around the world seven times and was detectable for five days.
Blue and green suns were observed as fine ash and aerosol erupted up to 50km into the stratosphere and circled the equator. In the following months these products spread to higher latitudes, causing vivid red sunset afterglows.
Recent research suggests that Edvard Munch’s iconic painting “The scream” (1884) depicts one such sunset over Christiania Harbour, Oslo, and that the figure was meant to represent “Nature” reacting in horror at the sight.
The volcanic dust veil that created such spectacular atmospheric effects also acted as a solar radiation filter, lowering global temperatures by as much as 1.2C in the year after the eruption. Temperatures did not return to normal until 1888.
