The Big Bang of 1883: Krakatoa Blows its Top

Arguably the most annoying and cantankerous guest who ever appeared at Fawlty Towers, the deaf Mrs Richards demanded a room with a sea view among many other things, but the view of Torquay from Room 22 was “not good enough” for her.  Basil Fawlty sarcastically asks what she expects to see from a Torquay hotel window:  Sydney Opera House, the hanging gardens of Babylon or herds of wildebeest sweeping majestically across the plains?  She demands a reduction of her bill, and Basil retorts “Why?  Because Krakatoa’s not erupting at the moment?”

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The view’s not good enough for this guest...

Had Mrs Richards indeed been in a hotel room observing Krakatoa on 27 August 1883 at 10:02 a m, she would certainly have heard it, as it was the loudest noise ever recorded in human history before or since, being heard in Perth, Australia, 3110 m (1930 miles) away and even across the Indian Ocean at Rodrigues Island, 4777 km (2968 miles) away.  To this island, not too far from Mauritius had come sounds like the roaring of distant heavy guns from the east as distant Krakatoa blew itself to pieces.  Travelling at the speed of sound the noise would have taken about four hours.

Hearing the sound like distant guns from Rodrigues would be equivalent to someone in Boston hearing a sound emanating across the Atlantic from Dublin, Ireland.

Sunda_strait_map_v4

If a sound causes air pressure fluctuations so extreme that the lower pressure reaches a vacuum, then the sound, instead of just passing through the air, pushes the air with it and creates a shock wave.  This usually occurs at about 194 decibels of sound.  The Krakatoa explosion registered 172 decibels at 100 miles from the source.  Compare this to standing next to a jet engine where you’d painfully experience around 150 decibels of sound.

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Area where the “Big Bang”of Krakatoa was heard

For five days following the explosion of Krakatoa (now more commonly spelt Krakatau), weather stations at 50 centres across the world recorded a huge spike in air pressure on their barographs, occurring roughly every 34 hours.  Because the shockwaves were travelling in opposite directions from the volcano, each station encountered the barometric spike up to seven times.  The first station to register this spike in air pressure was Calcutta, six hours and forty-seven minutes after the explosion.  Across the globe, New York, Washington DC and Toronto registered the spike 18 hours after the cataclysm.

Tidal stations in India, England and even San Francisco recorded a rise in ocean waves simultaneous with the air pulse.

As he transferred his meditations to pen in his ship’s log in the complete darkness, Captain Sampson was certain the Day of Judgement was at hand and thought of his wife at home, thousands of miles away, whom he thought he’d never see again.

The eardrums of half of his crew aboard Norham Castle, just 40 miles from Krakatoa, were burst by the sonic boom and he truly thought the end of the world had arrived, as it indeed had for at least 36 800 people from 165 towns and villages which were wiped out by the 30 metre (100 foot) high tsunami which shattered the Indonesian coast.

Probably the eruption of Mount Toba, near Lake Toba in present day Sumatra about 75 000 years ago produced more noise and destruction but no specimens of modern man were around to witness it.  This was a so-called super-eruption which, it is theorized, caused a global volcanic winter of 6-10 years and possibly an entire millennium of global cooling.  The erupted mass was 100 times greater than that of Mount Tambora in 1815, which led to the Year Without a Summer.  (We’ll discuss Tambora in another blog another day…)

It is also theorized that due to the global effects of the Toba supereruption it caused a genetic bottleneck in human development as well as in the development of other mammals, including tigers, cheetahs and chimpanzees, all of whom recovered from very low numbers around this time.

Prelude and Act One of the Krakatoa Drama

The island of Krakatoa, scene of the loudest dramatic production ever recorded is situated between Java and Sumatra in Indonesia.

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A depiction of Krakatoa in 1883

In the years preceding 1883, seismic activity in the area of Dutch East India (as Indonesia was then known) was intense and a number of earthquakes were reported which were felt as far as Australia.

The first indications of unusually high activity around Krakatoa were recorded from 20 May 1883 with regular steam venting from the northernmost of the island’s three cones and a number of explosions were heard as far afield as New Batavia, 160 km (100 miles) away.  Thus began the prelude to the display of light and sound which would follow.

After a few weeks of uneasy slumber the next phase of the volcano’s activities began around 16 June and ships at anchor had to be additionally moored with chains due to the uncommonly high tides.

Captain Ferzenaar, a Dutch topographical engineer, landed on the island on 11 August and noted an ash layer of 0.5 m (1.8 foot) high covering the island as well as the destruction of all vegetation.  Only tree stumps remained.  En route he observed three smoke columns obscuring the western part of the island, as well as at least eleven other steam vents.   He wisely advised against any further landings on the island.

COLLECTIE_TROPENMUSEUM_Groot_brok_koraal_uit_zee_dat_bij_Anjer_op_land_is_geworpen_na_de_uitbarsting_van_de_Krakatau_in_1883._TMnr_60005541
A large block of coral displaced by Krakatoa’s activity

The next day a passing ship reported a new vent just above sea level.  Volcanic activity continued throughout mid-August as Krakatoa made preparations for its climactic show.

Notably increased activity was bserved on 25 August and it is to be imagined that a good many people would have put as much distance between themselves and Krakatoa if they had any choice.

People watched the black plume of ash ascending 27 km (17 miles) into the atmosphere at around lunchtime on 26 August: this was the curtain raiser for the final act in the drama.

There were three other huge explosions which blew the heart of Krakatoa apart that dramatic day which began at dawn: 05:30, 06:44 and 10:41, but the big one which caused the worldwide shockwave was the one at 10:02.   Each one caused small tsunamis but the most destructive one was triggered at 10 a m.

The explosion at 05:30 originated from Perboewatan and sent a tsunami surging towards Telok Betong.

The explosion from Danan at 06:44 sent the resulting tsunami eastwards and westwards.

The biggest and loudest one was the one at 10:02.

At 10:41 the final large detonation was triggered by a landslide which tore off half of Rakata volcano.

Thereafter, having blown its top in the most dramatic way possible the volcanic activities decreased considerably and only

A  pyroclastic flow crossed the ocean and struck Ketimbang, 40 km (28 miles) north of Krakatoa on the island of Sumatra around noon, dropping hot ash which killed about 1000 people.

Not one person on the island of Sebesi, a mere 13 km (8 miles) from Krakatoa survived the eruption and its effects .

The town of Merak was devastated by a terrifying tsunami reaching as much as 46 m (151 feet) high.

Some parts of Java were never repopulated after Krakatoa and reverted to jungle, which is now part of the Ujung Kulon National Park.

Ships as far away as South Africa were rocked as remnants of the tsunamis made their way to distant places around the globe.

The topography of the islands had significantly altered and many places which were land, were now under water, and vice versa.

Among the numerous aftereffects was that the climate of the Northern Hemisphere decreased by up to  1.2 C. (2.2 F).  Chaotic weather patterns continued for years and temperatures didn’t return to normal until 1888.  The record rainfall which fell in Southern California between July 1883 and July 1884 has been attributed to the effects of Krakatoa.

An unusually high amount of sulphur dioxide was released into the stratosphere which high winds distributed throughout the planet, causing “acid rain” or rain with high amounts of sulphur dioxide.

Many parts of the world experienced spectacular red sunsets due to all the ash and dust in the atmosphere, and fire engines were called out in New York, Poughkeepsie and new Haven to quench the apparent conflagrations.  These unusually colourful sunsets continued for months and the red sky background in Edvard Munch’s The Scream has been proposed by an astronomer as an accurate depiction of the Norwegian sky following the eruption.  Had Munch’s subject been anywhere near Krakatoa in 1883 he’d certainly have covered his ears to drown out the cataclysmic sounds …

The Scream by Edvard Munch, 1893
The Scream by Edvard Munch, 1893

Born from the ocean waves and seismic action, Anak Krakatau (Child of Krakatoa) surfaced in August 1930 and gradually grew larger to complement the three islands which remained in the Krakatoa region after the eruption.  See map below:

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Anak Krakatau

Today Krakatoa seems peaceful.  But who knows what schemes she could be cooking up during her long but restless sleep?  This particular theatre of the Ring of Fire is volatile and always ready to produce a new drama on the ageless world stage.

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Satellite view of the islands, 18 May 1992

The Global Volcanism Programme, part of the Smithsonian Institution, keeps constant surveillance over Anak Krakatau and her neighbours so the people of the region have adequate warning of any ominous activity that could indicate a major eruption.  The last eruption was in 2014, with small emissions of smoke observed during June-July 2015.

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Diagram of Anak Krakatau, courtesy of Global Volcanism Programme
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Published by: envirozentinel63

Diagnosed with asperger syndrome. Keen runner and writer who wants to share the ups and downs of all my many experiences and maybe reach out to someone who needs encouragement.

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