Krakatoa

Awe meaning dread mixed with veneration. Awe meaning “solemn and reverential wonder, tinged with … fear, inspired by what is … sublime and majestic in nature,” according to the OED.

Toba.

Toba was the largest volcanic explosion of the past two million years. Toba Volcano blew 74,000 years ago.

Priscilla Long discusses volcanoes, destruction, and the true meaning of awesome. Read Toba.

(Photo via The Atlantic. Claudio Santana/AFP/Getty Images)

At 10:02 AM on August 27th, 1883, a volcanic island in modern day Indonesia called Krakatoa erupted. The blast sent shockwaves across the ocean, triggering tsunamis that destroyed the coast of Java and Sumatra. The sound was so loud it was heard 3000 miles away.

As Aatish Bhatia notes in this recent article:What we’re talking about here is like being in Boston and clearly hearing a noise coming from Dublin, Ireland.

Barometric readings at the time clocked the sound pressure at 172 decibels ONE HUNDRED MILES AWAY from the island.

Here’s a handy reference:

  • Using a jackhammer – 100 decibels
  • Human threshold for pain – 130 dB
  • Standing next to a jet engine – 150 dB

And the scale is logarithmic - so a 10 dB increase doubles the loudness.

Volcanoes seem to be a common topic these days. Yesterday Nautilus published a great piece by Aatish Bhatia on the 1883 eruption of Krakatoa, which tore the island apart and unleashed a sound so loud it was heard more than 4800 km away:

The British ship Norham Castle was 40 miles from Krakatoa at the time of the explosion. The ship’s captain wrote in his log, “So violent are the explosions that the ear-drums of over half my crew have been shattered. My last thoughts are with my dear wife. I am convinced that the Day of Judgement has come.“

In general, sounds are caused not by the end of the world but by fluctuations in air pressure. A barometer at the Batavia gasworks (100 miles away from Krakatoa) registered the ensuing spike in pressure at over 2.5 inches of mercury. That converts to over 172 decibels of sound pressure, an unimaginably loud noise. To put that in context, if you were operating a jackhammer you’d be subject to about 100 decibels. The human threshold for pain is near 130 decibels, and if you had the misfortune of standing next to a jet engine, you’d experience a 150 decibel sound. (A 10 decibel increase is perceived by people as sounding roughly twice as loud.) The Krakatoa explosion registered 172 decibels at 100 miles from the source. This is so astonishingly loud, that it’s inching up against the limits of what we mean by “sound.” #

Those are some mindbogglingly enormous numbers. Aatish does a wonderful job of explaining the science behind an explosion whose effects ricocheted through the atmosphere for days afterward. Check out the full article over at Nautilus.  (Image credit: Parker & Coward, via Wikipedia)

A Sound Heard Round the World

In 1883 just off the coast of Jakarta, a volcano on the tiny island of Krakatoa exploded. It had been building up for months, and on the morning of August 27th, the volcano erupted for the fourth time, blowing apart the entire island. It spewed out over twenty five cubic kilometres of ash, pumice, and rock, created tsunami waves over thirty metres high, and overall caused over 36,000 deaths. The eruption caused a shockwave of energy to tear around the globe seven times, and it was measured by barometers for a full five days afterwards. This peak explosion was about thirteen times larger than the Hiroshima bomb, and the sound it made was literally heard around the world: people heard it clearly as far flung as Perth, 3500 kilometres away in Australia, and even 5000 kilometres away, police officials mistook the eruption for “the distant roar of heavy guns.” The sound is estimated to have been around 180 decibels—as loud as a rifle shot at point blank range, and loud enough to instantly kill all hearing tissue in the human ear. It’s believed that Krakatoa’s eruption was one of the loudest sounds ever generated on Earth, rivalled only by the eruption of Mount Tambora in 1815, and the Tunguska event of 1908, when a meteroid or comet fragment exploded in the air above Russia. No wonder Krakatoa is considered the most dangerous volcano in human history.

Large, explosive volcanoes, like the 1883 eruption of Krakatoa, can temporarily alter global climate by injecting sulfurous gases into the high atmosphere. These aerosols cool Earth by slightly shading its surface, reflecting back to space some sunlight that would otherwise shine on it. The way volcanic aerosols reflect light produces vivid red sunsets. 

The red skies in Edvard Munch’s famous 1893 painting The Scream are now thought to reflect the eerie twilights seen in Norway for months after Krakatoa’s eruption. 

Learn more in the special exhibition, Nature’s Fury: The Science of Natural Disasters, open now through August 9.

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August 27, 1883: Krakatoa erupts.

The volcanic island of Krakatoa, located between the islands of Java and Sumatra, lay dormant for at least two centuries, before a passing European ship reported seeing enormous clouds of ash and dust rising from the area in May of 1883. Over the following months, volcanic activity in the region intensified, before reaching an apex on August 26th and 27th of that same year.

Four enormous explosions took place on August 27th, resulting in the destruction of at least two-thirds of the island. The sound produced by the eruption was so loud that it could be heard 3,000 miles away (on the island of Rodrigues in the Indian Ocean, the sound was initially thought to be the “roar of heavy guns”). The black clouds of ash spewed into the air by the volcano rose fifty miles high. Each of these colossal explosions was accompanied by tsunamis, which single-handedly killed off a large fraction of the (official) death toll, which was estimated at 36,000. Pyroclastic flow reached neighboring islands (including Sumatra) and wiped out vegetation, villages, and people. For months around the world, sunsets glowed unusually brilliant colors as a result of the gases emitted by the volcano; one British poet, Gerard Manley Hopkins, described this phenomenon:

…more like inflamed flesh than the lucid reds of ordinary sunsets… it bathes the whole sky, it is mistaken for the reflection of a great fire.

It is also sometimes theorized that Edvard Munch’s The Scream also depicts the after-effects of Krakatoa, similar as to what was described by Hopkins.

In modern terms, the eruption of Krakatoa is estimated to have had a yield of around 200 megatons; to put things into perspective, the “Fat Man” device detonated over Nagasaki had a yield of 21 kilotons, while Tsar Bomba, the most powerful nuclear weapon ever detonated, had a yield of 50 megatons. 

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The Eruption Of Mt. Krakatoa Was So Loud That It Circled The Earth Four Times [1]!

At 10:02 AM on August 27, 1883, a volcano on the island of Krakatoa had just erupted with a force so great that it tore the island apart. That island of Krakatoa sits between Java and Sumatra in Indonesia. The estimated human death toll ranges from 36,417, to over 120,000.

The sound of the volcano was so loud that it was heard almost 3000 miles away in Mauritius! You can understand why some people who had witnessed this event thought the world had come to an end. The eruption of Mt. Krakatoa is the most distant sound that has ever been heard in recorded history, but how loud was it? 

According to Aatish Bhatia, the Krakatoa explosion “registered 172 decibels at 100 miles from the source”. To put that number in context, imagine that you had the misfortune of standing next to a jet engine. If you did that, you would experience a 150 decibel sound, which is above the human threshold for pain at around 130 decibels [2].

Needless to say, closer to Krakatoa, the sound was way more powerful than that. The article [1] will tell you more about the eruption that produced pressure waves so powerful that it circled the globe three to four times in each direction

Notes and References:

[1] Article source: Bhatia, A.   The Sound So Loud That It Circled the Earth Four Times. Nautil.us, September 29 (2014).

[2] A 10 decibel increase is perceived by people as sounding roughly twice as loud. See Also: What is a decibel, and how is it measured?

[3] Picture credits: TOP: Artist’s rendering of Kratatoa from [1], MIDDLE: a map of Krakatoa before and after the 1883 eruption. COURTESY: USGS and Wikipedia. BOTTOM: Krakatoa spewing lava in modern times. COURTESY: The Guardian.

Submitted by Srikar D., Discoverer.

Edited by Bradly A.

vimeo

16 Million Particles Underwater (via Rigel Bowen)

16 Million TP Particles driven by a FumeFx sim rendered in Krakatoa.
Finished in AE CS5.