KrakatoaThe Explosion Heard Round the World |
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By Duke Heath
Later in this issue we will look at a couple of the greatest volcanos in history. One of them nearly wiped out the human race and the other devastated the entire United States and may do so again very soon. To understand the magnitude of the explosions of those two super volcanos, I want to focus on the largest explosion ever heard in recorded history. The magnitude of the explosion we are about to examine is a fraction of the two super volcanos we will look at later in this issue.
On August 26, 18$3 the Indonesian island of Krakatau exploded with devastating fury. The eruption was one of the most catastrophic natural disasters in modern times. The effects of this explosion were experienced around the world. Ash from the eruption fell as far away as New York. Volcanic dust filled the upper levels of the atmosphere and changed the Earth's weather for several years.
Several tidal waves, some much more than a hundred feet high, radiated out from the colossal event throughout the Indian Ocean, across the Pacific Ocean and even reaching as far away as the English Channel. The waves were so powerful that they hurled coral rocks onshore weighing more than 600 tons each. 36,000 people were killed as these giant waves destroyed 165 coastal villages.
Krakatoa had been silent for about 200 years when seismic activity began increasing. On May 20, the volcano became active. The initial explosive eruptions of Krakatoa could be heard 100 miles away. Steam and ash could be seen rising several miles into the sky.
By August 11, 1883, three vents were actively erupting. Eleven other vents were ejecting smaller quantities of steam, ash and dust. By the August 26, explosions were occurring every ten minutes. Sailors on ships a hundred miles away reported a black cloud of smoke rising above the volcano. The volcanos central vent was blacked by a solid plug of lava and the pressure underneath it had begun increasing rapidly.
Through the 4,157 mile long Nile was all-important
to Egypt, Europeans were the first to trace the Nile to Its source.
In 1857, John Speke reached a great equatorial lake that he named
Lake Victoria, for his Queen. Many rivers flowed into the lake,
but the Nile issued from it.
At this time, Krakatoa's crater was about 1000 meters in diameter with a depth of about SO meters. (Compare this with the size of Yellowstone's caldera at 53 miles by 28 miles.) As the walls of the volcano began to collapse, sea water poured into the volcano's caldera. The superheated steam created tremendous pressure. The resultant explosion blew the island apart. This was the most severe volcanic explosion in modem times. A cloud of ash rose 17 miles into the atmosphere.
The explosion of Krakatoa was equivalent to a 200 megaton nuclear bomb. By contrast, the Hiroshima bomb was less than 20 kilotons. The eruption has been assigned a Volcanic Explosive index of 6. This rates as colossal. The volume of earth displaced by the explosion was estimated to be between 14 and 100 cubic kilometers.
The amount of material ejected into the upper atmosphere has been estimated to be about l I cubic miles. This dust cloud completely covered the area. The skies were dark 260 miles away. The darkness lasted more than three days.
Pumice from the eruption formed large thick floating rafts which crossed the Indian Ocean and remained floating for two years following the eruption. Ash fell on ships thousands of miles away.
The sound of the explosion was heard far thousands of miles, covering almost a third of the earth's surface. The echoes of the explosion continued reverberating for several hours. Atmospheric pressure shock waves circled the earth at least seven times and were recorded by every barograph throughout the world over the next five days.
The ash which was ejected into the atmosphere caused major climatic changes world wide. The average temperature of the planet fell 1.2 degrees and did not return to normal for five years.
Three months after the eruption the ash caused such vivid red sunset afterglows that fire engines were called out in New York, Poughkeepsie, and New Haven to quench the apparent conflagration. Unusual sunsets continued for 3 years.
Five year old Arshile Gorky, the future nonobjective
painter, stopped talking when his father walked out on the family.
He began to speak again only when he cried out in dismay on seeing
his tutor leap from a cliff; the tutor had only been pretending,
but the stunning sight restored Arshile's speech.