On August 27, 1883 four massive volcanic explosions took place at the island of Krakatoa in Indonesia producing the loudest sound ever recorded in history. The eruption and the resulting tsunamis caused the death of at least 36,000 people making it one of the worst natural disasters in modern times. Here are 10 interesting facts about the cause, measure on the VEI scale, death toll and effects of the 1883 eruption of Krakatoa.

 

#1 Volcanic activity in Krakatoa is due to movement of the Indo-Australian tectonic plate

Indonesia has over 130 active volcanoes, the most of any nation. The Sunda Strait is the strait between the Indonesian islands of Java and Sumatra. Krakatoa (Indonesian: Krakatau) is a volcanic island situated in the Sunda Strait in the Indonesian province of Lampung. It is part of the Indonesian Island Arc. Volcanic activity in the island arc is due to the lower part of the Indo-Australian tectonic plate moving northwards at a higher pace than the upper part, whose movement is hindered by the Himalayas.

Indo-Australian tectonic plate
Indo-Australian tectonic plate

 

#2 Rakata was the only volcanic cone to partially survive the 1883 eruption

Prior to the 1883 eruption, Krakatau had three linked volcanic cones. Perboewatan was the northernmost of the cones. It was the lowest with a height of 122 meters (400 ft) and the most active. Rakata was the southernmost of the three cones and the largest with a height of 813 meters (2,667 ft). Danan, the third volcanic cone, lay in the middle and stood at 450 meters (1,480 ft). Rakata was the only one of the three volcanoes that was not totally destroyed in the eruption of 1883. It lost its northern half in the eruption leaving only its southern half.

Map of Krakatoa - before and after eruption
Map of Krakatoa after the 1883 eruption showing the change in geography

 

#3 It entered into a phase of volcanic activity from May 20, 1883

In the years leading to the 1883 eruption of Krakatoa, there was intense seismic activity around the volcano with earthquakes felt as far away as Australia. On 20th May 1883, Perboewatan became active. Ash-laden clouds reached a height of 6 kilometers and explosions could be heard. Though the activity died down by the end of May, eruptions started again around June 16. Over the next 2 months, there were regular small blasts from Krakatoa out of the three vents; and reports of thundering noises and incandescent clouds.

Krakatoa before the 1883 eruption
A sketch of Krakatoa, most likely Rakata, before the 1883 eruptions

 

Depiction of 1883 eruption of Krakatoa
An 1888 lithograph of the 1883 eruption of Krakatoa

#4 Krakatoa eruption consisted of 4 enormous explosions on 27th August

The eruptions of Krakatoa intensified till August 25 and around noon on August 26, the volcano sent an ash cloud 20 miles into the air and tremors triggered several tsunamis. On 27th August, four enormous explosions took place at 05:30, 06:44, 10:02 and 10:41. Each explosion was accompanied by large tsunamis which were reported to be over 30 meters (98 feet) high in places. The explosions plunged both Perboewatan and Danan into the caldera below the sea.

#5 It created the loudest sound ever recorded in history

The colossal fourth and final explosion of Krakatoa made the loudest sound ever recorded on the planet. It could be heard as far away as central Australia and the island of Rodrigues, 3,000 miles from Krakatoa. It was so loud that it ruptured the eardrums of sailors 64 km (40 miles) away on ships in the Sunda Strait. The air waves created by the eruption were detected at points all over the earth. Barographs recorded the wave seven times over the course of five days. Hence the wave rounded the globe three and a half times.

 

#6 The 1883 Krakatoa eruption was a VEI-6 event

The volcanic explosivity index (VEI) is used to measure the explosiveness of volcanic eruptions. The 1883 Krakatoa eruption is classified as a VEI-6 event, i.e. it ejected more than 10 cubic kilometers of tephra (material produced by a volcanic eruption) and the eruption cloud height was more than 20km. The energy released from the explosion has been estimated to be equal to about 200 megatons of TNT, about 13,000 times more powerful than the Little Boy bomb (13 to 16 kt) that devastated Hiroshima during World War II, and four times more than Tsar Bomba (50 Mt), the most powerful nuclear device ever detonated.

VEI Index of volcanic eruptions
VEI Index of volcanic eruptions

 

#7 The 1883 eruption of Krakatoa caused the death of at least 36,000 people

Around noon on 27 August 1883, pyroclastic flows from the Krakatoa eruption killed about 1,000 people at Ketimbang, some 48 km north of the island. But the most devastating effect was the tremendous tsunamis caused by the eruption that overwhelmed hundreds of villages on the coasts of Java and Sumatra. At the time of the eruption, Krakatoa came under Dutch East Indies. The Dutch authorities recorded a death toll of 36,417. However exact numbers are impossible to determine. Some estimates even putting the death toll at more the 120,000. 1883 Krakatoa eruption is one of the deadliest natural disasters of modern times.

Deadliest volcanic eruptions
Deadliest volcanic eruptions

 

#8 It caused a drop in temperatures in the Northern hemisphere the following year

The Scream - Edvard Munch
The Scream – Edvard Munch

Due to the rock, ash and pumice which were thrown to the atmosphere as a result of the eruption, the surrounding region was plunged into darkness for two and a half days. Mixed with the material were millions of tonnes of sulfur dioxide. A large portion of this rose up into the stratosphere and then oxidized to form sulfate ions. These developed into tiny particles which reflected a fraction of the light from the sun. With less sunlight, average Northern Hemisphere summer temperatures fell by as much as 1.2 °C (2.2 °F) the following year. Weather patterns continued to be chaotic till 1888.

#9 It might have a relation to Munch’s masterpiece The Scream

Due to the 1883 eruption of Krakatoa, fine dust particles spread in the stratosphere causing the sun to appear in strange colors to people around the world. Over three months after the eruption spectacular sunsets were seen throughout the world. In one case, fire engines in Poughkeepsie, New York, were dispatched as people watching a red sunset became convinced that they were seeing a fire in the distance. In 2004, an astronomer proposed that famous Norwegian painter Edvard Munch’s 1893 masterpiece The Scream depicts in its background the sky over Norway after the eruption.

#10 A new island called Anak Krakatau has emerged from the caldera formed in 1883

The 1883 Krakatoa eruption destroyed most of the island with only a small fraction surviving. Small eruptions continued in the following months and in February 1884, after which volcanic activity seized. Krakatoa was quiet until December 1927, when a new eruption was reported. In early 1928, a rising cone reached sea level, and by 1930 it had become a small island called Anak Krakatau (“Child of Krakatoa”). It is growing at an average of five inches every week. Anak Krakatau has remained in focus in the scientific community as it gives a chance to see how island ecosystems are established from scratch.

Anak Krakatau in 2008
Volcanic activity at Anak Krakatoa, 2008

 

The First Recorded Observation of Bishop’s Ring

A Bishop’s Ring is a diffuse brown or bluish halo observed around the sun, typically after large volcanic eruptions. Sulfur compound aerosols derived from volcanic eruptions are considered responsible for this rare phenomenon. The first recorded observation of a Bishop’s Ring was done on September 5, 1883, after the 1883 eruption of Krakatoa, by Rev. Sereno Edward Bishop, after whom the phenomenon has been named.

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