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14 Interesting Facts About the Krakatoa Volcano
The Krakatoa volcano erupted in the year 1883, killing as many as 36,000 people. We will take you through the details of this disaster and the effects it had on the environment and the world.
Did You Know?
The effects of the Krakatoa eruption that led to the red, vivid sunsets is believed to be the inspiration for Edvard Munch’s famous painting ‘The Scream’.
The Krakatoa Island
The Krakatoa (kra-kuh-tow-uh) island is situated in the Sunda Strait, between Java and Sumatra, and forms a part of the Indonesian Island Arc. The Krakatoa volcano on the island that had been dormant for 200 years exploded on the 26th of August, 1883, destroying not only the island, but claiming the lives of more than 36,000 people, and causing damage to the surrounding property, and negative changes in the environment.
The aftermath of the eruption was felt for several months after the incident and the disaster has been recorded as one of the worst in the history of the world. In this following ScienceStruck article, we will provide you with the history, information, and other facts about the Krakatoa volcano.
Krakatoa Volcano Facts
The Island of Krakatoa as it Was
The Krakatoa island (also known as ‘Krakatau’) is situated near the Indonesian island of Rakata in western Indonesia, in the Sunda Strait between Java and Sumatra. The island was about 5.5 miles long and 3 miles wide.
The Krakatoa Islands before the eruption
Before the explosion, the island had 3 linked volcanic peaks (composite volcano), these being―Perboewatan, which was the northernmost peak and also the most active; the Danan peak, which was situated in the middle; and the Rakata, which was the largest and formed the southernmost end of the island.
The Krakatoa Islands after the eruption
The Krakatoa, along with two nearby islands, Verlatan and Lang are remnants of a large eruption that had taken place previously and left an undersea caldera (crater) between them.
The Warning Signs Before the Eruption
2-3 months prior to the incident, many passing ships, commercial vessels, and chartered sightseeing boats in the Indian ocean would witness and report of several abnormal happenings around the volcano. They reported of black clouds hovering above the volcano and thundering noises. By August 1, three vents were seen to be regularly erupting on the volcano.
During this time, the tides were also reported as being unusually high, and the water was so unsteady that the ships at anchor were required to be tied down with chains. Reports of windows shattering without any apparent reason were also quite common.
Why the Eruption Occurred
The Krakatoa eruptions were caused by the subduction of the Indo-Australian tectonic plate as it moved northward towards mainland Asia. Subduction is a geological process by which one edge of a crustal plate is forced sideways and downward into the mantle below another plate.
And then the Eruptions Happened
On 26th August, around 12.53 p.m., the initial blast of the eruption is said to have sent a cloud of gas and debris into the air above Perboewatan, at an estimated 15 miles per hour. It is said that the earlier eruptive activity must have plugged the neck of the cone of the volcano, thus allowing pressure to build in the magma chamber. This caused black soot and ashes to circulate the islands around Krakatoa.
The black soot and hot ashes rained down on the people, causing panic and fear among them. From time to time, a red, fiery glare was spotted over the volcano as well. The sea turned more violent, and waves crashed against the shore, shattering boats at the harbor to smithereens. Shortly after, the telegraph lines went dead.
All night through, the eruptions continued, sending flying cinders and ash into the air. On the dawn of the 27th, the first explosion began at 5.30 am. and was followed by 3 more explosions at 6:42 am., 8:20 am., and 10:02 am.
Pyroclastic Flows Caused This
The last of the eruptions that took place at 10:02 am. opened fissures in the walls of the volcano, thus allowing sea water to pour into the magma chamber and come in contact with the hot lava―this event is known as a phreatomagmatic event. As a result of this, the water flash-boiled and created a cushion of superheated steam that carried the pyroclastic flows up to 25 miles, recording speeds in excess of 62mph.
Destruction of the Island
With the last explosion, both, the Danan and Perboewatan were plunged into the crater below the sea and only a 3rd of the Krakatoa island remained above sea level. The rest of the island that the volcano had stood on, exploded into nothingness. New islands made of steaming pumice and ash were formed, these lay to the north where the sea had been 36 m deep.
The Sound and Rating on the VEI
It has been recorded that the sound that these eruptions caused was so deafening and loud that it could be heard about 2,800 miles away in Perth, Australia. Buildings that were 500 miles away shook with the impact.
The Volcanic Explosion Index has assigned a rating of 6 to the eruptions and it is estimated to have had an explosive force of 200 megatons of TNT. To put things into perspective, the bomb that was used against Hiroshima had a force of 20 kilotons and the Mount St. Helens explosion that took place in 1980, had a VEI of 5.
Tsunamis and Volcanic Ashes Followed
The deadliest effect of the eruptions was the subsequent tsunamis that took place, which were responsible for the maximum number of deaths. When the volcano collapsed into the sea, it created a wall of water, nearly 120 feet tall, that moved out from Krakatoa at 60 miles per hour.
The force with which the tsunami bore down on the coastal areas of western Java and southern Sumatra, caused the devastation of more than 165 coastal regions―wiping out Sirik and Semarang in Java and Telok Batong in Sumatra.
In addition to the tsunami, there was superheated volcanic ash that rushed across the surface of the ocean, killing thousands more. Although no one was known to have been killed because of the initial explosion, the subsequent tsunamis and ashes is known to have collectively led to the death of 36, 417 people.
It Caused Darkened Skies
The explosions hurled (an estimated) 11 cubic miles of debris into the air―causing a darkening of the skies up to 275 miles from the site of the volcano. In the immediate vicinity of Krakatoa, light did not return for 3 days.
And Also, Lonely, Lonely Lands
The ash and pumice that settled into the ground after the eruptions, led to the land being turned useless―plants could not grow for several years after the incident.
Atmospheric Pressure Wave
After the eruptions, the passage of the atmospheric pressure wave was recorded, and it is said that it was documented as many as 7 times, as the wave bounced back and forth between the eruption site and its antipodes for 5 days after the eruption.
It Set the Sunsets on Fire
As fine ash, sulfur dioxide, and aerosol erupted into the stratosphere, and circled the equator for 13 days, blue and green suns were observed. Three months after the eruptions, these particles had spread to higher latitudes, and filtered the amount of sunlight that would reach the Earth. As a result of this phenomenon, spectacular and vivid red sunsets were observed all over the United States and Europe. These unusual sunsets continued for 3 years.
And the Temperatures Dropped
The heavy cover of debris that rose up to the stratosphere also acted as a solar radiation filter and led to the lowering of global temperatures by 1.2 ºC in the year after the disaster. Temperatures did not return to normal for 5 years after the eruption.
The Floating Phenomenon Took Place
Bodies of victims were seen floating in the Indian Ocean for several weeks after the explosion. Along with that, the hot lava that flowed into the ocean caused for masses of volcanic pumice to be formed. There are reports of skeletons and bodies floating across these rafts in the Indian Ocean―some even washing up on the east coast of Africa for over 2 years after the eruption.
And the Krakatoa Lives On
As the peaks of the Krakatoa blasted itself out of existence, a small part of the island survived. In 1927, it emerged from under the ocean from the collapsed crater that was created during the 1883 eruption as a column of steam and debris which spewed above. The Krakatoa had awakened after 44 years of calm.
Within a few weeks of this incident, the rim of a new cone appeared above the sea level; and within a year, it grew into a small island―the island was called the Anak Krakatoa, which translates to Child of Krakatoa.
Anak Krakatoa has continued to erupt since its inception in 1927, though mildly. However, once or twice a year it has slightly stronger eruptions which are reported.
The Anak Krakatoa is a subject of great interest for geologists all over the world. The chances of a 1883-style eruption taking place again are very small, however, the possibility cannot be ruled out. There are warnings issued against getting too close to the Anak Krakatoa because even a small collapse of the same could cause another tsunami that might be devastating, to say the least.