1883 eruption of Krakatoa
Encyclopedia
The 1883 eruption of Krakatoa began in May 1883 and culminated with the destruction of Krakatoa
on 27 August 1883. Minor seismic activity continued to be reported until February 1884, though reports after October 1883 were later dismissed by Rogier Verbeek
's investigation.
s felt as far as Australia. Beginning 20 May 1883, three months before the final explosion, steam venting began to occur regularly from Perbuatan, the northernmost of the island's three cones. Eruptions of ash reached an altitude of 6 km (20,000 ft) and explosions could be heard in New Batavia (Jakarta) 160 km (99 mi) away. Activity died down by the end of May, with no records of activity until mid-June.
Eruptions started again around 16 June, when loud explosions were heard and a thick black cloud covered the islands for five days. On 24 June an east wind blew this cloud away and two ash columns were seen issuing from Krakatoa. The new seat of the eruption is believed to have been a new vent or vents which formed between Perbuatan and Danan, near the location of the volcanic cone of Anak Krakatau. The violence of the eruption caused tides in the vicinity to be unusually high, and ships at anchor had to be moored with chains as a result. Earthquake shocks began to be felt at Anyer (Java), and large pumice
masses started to be reported by ships in the Indian Ocean to the west.
On 11 August, H.J.G. Ferzenaar investigated the islands. He noted three major ash columns (the newer from Danan), which obscured the western part of the island (the wind blows primarily from the east at this time of year), and steam plumes from at least eleven other vents, mostly between Danan and Rakata. Where he landed, he found an ash layer about 0.5 m (1 ft 8 in) thick; all vegetation had been destroyed, with only tree stumps left. He advised against any further landings. The next day, a ship passing to the north reported a new vent "only a few meters above sea level" (this may be the most northerly spot indicated on Ferzenaar's map). Activity continued through mid-August.
up to 10 cm (3.9 in) in diameter landing on their decks. A small tsunami
hit the shores of Java and Sumatra
some 40 km (24.9 mi) away between the time of 18:00 and 19:00 hours.
On 27 August four enormous explosions took place at 05:30, 06:44, 10:02, and 10:41 local time. The explosions were so violent that they were heard 3500 km (2,174.8 mi) away in Perth
, Western Australia
and the Indian Ocean
island of Rodrigues
near Mauritius
, 4800 km (2,982.6 mi) away, where they were thought to be cannonfire from a nearby ship. Each was accompanied by very large tsunami
s, which are believed to have been over 30 meters (100 ft) high in places. A large area of the Sunda Strait
and a number of places on the Sumatran coast were affected by pyroclastic flow
s from the volcano.
The pressure wave generated by the colossal final explosion radiated from Krakatoa at 1086 km/h (674.8 mph). It was so powerful that it ruptured the eardrums of sailors on ships in the Sunda Strait and caused a spike of more than two and half inches of mercury (ca 85 hPa) in pressure gauges attached to gasometer
s in the Jakarta gasworks, sending them off the scale. The pressure wave radiated across the globe and was recorded on barograph
s all over the world, which continued to register it up to 5 days after the explosion. Barograph recordings show that the shockwave from the final explosion reverberated around the globe 7 times in total. Ash was propelled to a height of 80 km (49.7 mi).
The eruptions diminished rapidly after that point, and by the morning of August 28 Krakatoa was silent. Small eruptions, mostly of mud, continued through October, though further October 1883.
Province) in Sumatra. Around a thousand people were killed, the only large number of victims killed by Krakatoa itself, and not the waves or after-effects. Verbeek and later writers believe this unique event was a lateral blast
or pyroclastic surge
(similar to the catastrophic 1980 eruption of Mount Saint Helens), which crossed the water. The region of the ashfall ended to the northwest of Ketimbang, where the bulk of Sebesi
Island offered protection from any horizontal surges.
s had disastrous results in the region. There were no survivors from 3,000 people located at the island of Sebesi
, about 13 km (8.1 mi) from Krakatoa. Pyroclastic flows killed around 1,000 people at Ketimbang on the coast of Sumatra some 40 km (24.9 mi) north from Krakatoa. The official death toll recorded by the Dutch authorities was 36,417, although some sources put the estimate at 120,000 or more. Many settlements were destroyed, including Teluk Betung and Ketimbang in Sumatra
, and Sirik and Serang
in Java. The areas of Banten
on Java and the Lampung
on Sumatra
were devastated. There are numerous documented reports of groups of human skeleton
s floating across the Indian Ocean
on rafts of volcanic pumice
and washing up on the east coast of Africa
, up to a year after the eruption. Some land on Java was never repopulated; it reverted to jungle
and is now the Ujung Kulon National Park
.
rocked as tsunamis hit them, and the bodies of victims were found floating in the ocean for weeks after the event. The tsunamis which accompanied the eruption are believed to have been caused by gigantic pyroclastic flow
s entering the sea; each of the four great explosions was accompanied by a massive pyroclastic flow resulting from the gravitational collapse of the eruption column. This caused several cubic kilometers of material to enter the sea, displacing an equally huge volume of seawater. The town of Merak was destroyed by a tsunami 46 m (150.9 ft) high. Some of the pyroclastic flows reached the Sumatran coast as much as 40 km (24.9 mi) away, having apparently moved across the water on a "cushion" of superheated steam. There are also indications of submarine pyroclastic flows reaching 15 km (9.3 mi) from the volcano.
A recent documentary film showed tests made by a research team at the University of Kiel
, Germany
, of pyroclastic flows moving over water. The tests revealed that hot ash travelled over the water on a cloud of superheated steam, continuing to be a pyroclastic flow after crossing water; the heavy matter precipitated out of the flow shortly after initial contact with the water, creating a tsunami due to the precipitate mass.
Smaller waves were recorded on tidal gauges as far away as the English Channel
. These occurred too soon to be remnants of the initial tsunamis, and may have been caused by concussive air waves from the eruption. These air waves circled the globe several times and were still detectable using barograph
s five days later.
. Of the northern two-thirds of the island, only a rocky islet named Bootsmansrots ('Bosun's Rock', a fragment of Danan) was left; Poolsche Hoed
had disappeared.
As a result of the huge amount of material deposited by the volcano, the surrounding ocean floor was drastically altered. It is estimated that as much as 18 cubic kilometre of ignimbrite
was deposited over an area of 1100000 km² (424,712.4 sq mi), largely filling the 30 metre deep basin around the mountain. The land masses of Verlaten and Lang were increased, as was the western part of the remnant of Rakata. Much of this gained material quickly eroded away, but volcanic ash continues to be a significant part of the geological composition of these islands.
Two nearby sandbanks (called Steers
and Calmeyer
after the two naval officers who investigated them) were built up into islands by ashfall, but the sea later washed them away. Seawater on hot volcanic deposits on Steers and Calmeyer caused steam which some people mistook for continued eruption.
(SO2) gas high into the stratosphere
which was subsequently transported by high-level winds all over the planet. This led to a global increase in sulfurous acid
(H2SO3) concentration in high-level cirrus cloud
s. The resulting increase in cloud reflectivity
(or albedo
) would reflect more incoming light from the sun than usual, and cool the entire planet until the suspended sulfur
fell to the ground as acid precipitation.
made thousands of colour sketches of the red sunsets half-way around the world from Krakatoa in the years after the eruption.
In 2004, an astronomer proposed the idea that the blood-red sky shown in Edvard Munch
's famous 1893 painting The Scream
is also an accurate depiction of the sky over Norway
after the eruption. This explanation has been disputed by art scholars who note that Munch was an expressive rather than descriptive painter.
Weather watchers of the time tracked and mapped the effects on the sky. They labeled the phenomenon the "equatorial smoke stream". This was the first identification of what is known today as the Jet stream
.
This eruption also produced a Bishop's Ring
around the sun by day, and a volcanic purple light at twilight.
at the end of the eruption sequence, rather than having been destroyed during the eruptions.
The main theories are:
Both these ideas assumed that the island subsided before the explosions; however, the evidence does not support that conclusion and the pumice and ignimbrite deposits are not of a kind consistent with a magma-seawater interaction.
No signs of activity were seen in the next several years until 1913, when an eruption was reported. Investigation could find no evidence the volcano was awakening, and it was determined that what had been mistaken for renewed activity had actually been a major landslide (possibly the one which formed the second arc to Rakata's cliff).
Examinations after 1930 of bathymetric charts made in 1919 show evidence of a bulge indicative of magma
near the surface at the site that became Anak Krakatau.
Krakatoa
Krakatoa is a volcanic island made of a'a lava in the Sunda Strait between the islands of Java and Sumatra in Indonesia. The name is used for the island group, the main island , and the volcano as a whole. The island exploded in 1883, killing approximately 40,000 people, although some estimates...
on 27 August 1883. Minor seismic activity continued to be reported until February 1884, though reports after October 1883 were later dismissed by Rogier Verbeek
Rogier Verbeek
Rogier Diederik Marius Verbeek was a Dutch geologist and nature scientist.His journal Krakatau, which was edited in 1884 and 1885 by order of the Governor-General of the Dutch East Indies, is his most known work. It deals with the eruption of the volcanic island Krakatoa in 1883 and brought...
's investigation.
Early phase
In the years before the 1883 eruption, seismic activity around the volcano was intense, with some earthquakeEarthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s felt as far as Australia. Beginning 20 May 1883, three months before the final explosion, steam venting began to occur regularly from Perbuatan, the northernmost of the island's three cones. Eruptions of ash reached an altitude of 6 km (20,000 ft) and explosions could be heard in New Batavia (Jakarta) 160 km (99 mi) away. Activity died down by the end of May, with no records of activity until mid-June.
Eruptions started again around 16 June, when loud explosions were heard and a thick black cloud covered the islands for five days. On 24 June an east wind blew this cloud away and two ash columns were seen issuing from Krakatoa. The new seat of the eruption is believed to have been a new vent or vents which formed between Perbuatan and Danan, near the location of the volcanic cone of Anak Krakatau. The violence of the eruption caused tides in the vicinity to be unusually high, and ships at anchor had to be moored with chains as a result. Earthquake shocks began to be felt at Anyer (Java), and large pumice
Pumice
Pumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid...
masses started to be reported by ships in the Indian Ocean to the west.
On 11 August, H.J.G. Ferzenaar investigated the islands. He noted three major ash columns (the newer from Danan), which obscured the western part of the island (the wind blows primarily from the east at this time of year), and steam plumes from at least eleven other vents, mostly between Danan and Rakata. Where he landed, he found an ash layer about 0.5 m (1 ft 8 in) thick; all vegetation had been destroyed, with only tree stumps left. He advised against any further landings. The next day, a ship passing to the north reported a new vent "only a few meters above sea level" (this may be the most northerly spot indicated on Ferzenaar's map). Activity continued through mid-August.
Climactic phase
By 25 August, eruptions further intensified. At about 13:00 (local time) on 26 August, the volcano went into its paroxysmal phase, and by 14:00 observers could see a black cloud of ash 27 km (16.8 mi) high. At this point, the eruption was virtually continuous and explosions could be heard every ten minutes or so. Ships within 20 km (12.4 mi) of the volcano reported heavy ash fall, with pieces of hot pumicePumice
Pumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid...
up to 10 cm (3.9 in) in diameter landing on their decks. A small tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...
hit the shores of Java and Sumatra
Sumatra
Sumatra is an island in western Indonesia, westernmost of the Sunda Islands. It is the largest island entirely in Indonesia , and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538...
some 40 km (24.9 mi) away between the time of 18:00 and 19:00 hours.
On 27 August four enormous explosions took place at 05:30, 06:44, 10:02, and 10:41 local time. The explosions were so violent that they were heard 3500 km (2,174.8 mi) away in Perth
Perth, Western Australia
Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....
, Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
and the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
island of Rodrigues
Rodrigues (island)
Rodrigues , sometimes spelled Rodriguez but named after the Portuguese explorer Diogo Rodrigues, is the smallest of the Mascarene Islands and a dependency of Mauritius...
near Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...
, 4800 km (2,982.6 mi) away, where they were thought to be cannonfire from a nearby ship. Each was accompanied by very large tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...
s, which are believed to have been over 30 meters (100 ft) high in places. A large area of the Sunda Strait
Sunda Strait
The Sunda Strait is the strait between the Indonesian islands of Java and Sumatra. It connects the Java Sea to the Indian Ocean...
and a number of places on the Sumatran coast were affected by pyroclastic flow
Pyroclastic flow
A pyroclastic flow is a fast-moving current of superheated gas and rock , which reaches speeds moving away from a volcano of up to 700 km/h . The flows normally hug the ground and travel downhill, or spread laterally under gravity...
s from the volcano.
The pressure wave generated by the colossal final explosion radiated from Krakatoa at 1086 km/h (674.8 mph). It was so powerful that it ruptured the eardrums of sailors on ships in the Sunda Strait and caused a spike of more than two and half inches of mercury (ca 85 hPa) in pressure gauges attached to gasometer
Gasometer
A gas holder is a large container where natural gas or town gas is stored near atmospheric pressure at ambient temperatures. The volume of the container follows the quantity of stored gas, with pressure coming from the weight of a movable cap...
s in the Jakarta gasworks, sending them off the scale. The pressure wave radiated across the globe and was recorded on barograph
Barograph
A barograph is a recording aneroid barometer. It produces a paper or foil chart called a barogram that records the barometric pressure over time....
s all over the world, which continued to register it up to 5 days after the explosion. Barograph recordings show that the shockwave from the final explosion reverberated around the globe 7 times in total. Ash was propelled to a height of 80 km (49.7 mi).
The eruptions diminished rapidly after that point, and by the morning of August 28 Krakatoa was silent. Small eruptions, mostly of mud, continued through October, though further October 1883.
"The Burning Ashes of Ketimbang"
Around noon on August 27, a rain of hot ash fell around Ketimbang (now Katibung in LampungLampung
Lampung is a province of Indonesia. It is located on the southern tip of the island of Sumatra and borders the provinces of Bengkulu and South Sumatra. Lampung is the original home of the Lampung people, who speak a distinct language from other people in Sumatra and have their own alphabet. Its...
Province) in Sumatra. Around a thousand people were killed, the only large number of victims killed by Krakatoa itself, and not the waves or after-effects. Verbeek and later writers believe this unique event was a lateral blast
Lateral eruption
A lateral eruption, also called a flank eruption or lateral blast if explosive, is a volcanic eruption that takes place on the flanks of a volcano instead of at the summit. Lateral eruptions are typical at rift zones where a volcano is breaking apart...
or pyroclastic surge
Pyroclastic surge
A pyroclastic surge is a fluidized mass of turbulent gas and rock fragments which is ejected during some volcanic eruptions. It is similar to a pyroclastic flow but it has a lower density or contains a much higher proportion of gas to rock ratio, which makes it more turbulent and allows it to rise...
(similar to the catastrophic 1980 eruption of Mount Saint Helens), which crossed the water. The region of the ashfall ended to the northwest of Ketimbang, where the bulk of Sebesi
Sebesi
Sebesi is an Indonesian island in the Sunda Strait, between Java and Sumatra. It rises to a height of and lies about 12 km to the north of the Krakatoa Islands and is the closest large island, about the same area and height as the remmant of Rakata. Like Krakatoa, it too is volcanic, although...
Island offered protection from any horizontal surges.
Effects
The combination of pyroclastic flows, volcanic ashes and tsunamiTsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...
s had disastrous results in the region. There were no survivors from 3,000 people located at the island of Sebesi
Sebesi
Sebesi is an Indonesian island in the Sunda Strait, between Java and Sumatra. It rises to a height of and lies about 12 km to the north of the Krakatoa Islands and is the closest large island, about the same area and height as the remmant of Rakata. Like Krakatoa, it too is volcanic, although...
, about 13 km (8.1 mi) from Krakatoa. Pyroclastic flows killed around 1,000 people at Ketimbang on the coast of Sumatra some 40 km (24.9 mi) north from Krakatoa. The official death toll recorded by the Dutch authorities was 36,417, although some sources put the estimate at 120,000 or more. Many settlements were destroyed, including Teluk Betung and Ketimbang in Sumatra
Sumatra
Sumatra is an island in western Indonesia, westernmost of the Sunda Islands. It is the largest island entirely in Indonesia , and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538...
, and Sirik and Serang
Serang
Serang is a regency of Banten province, Indonesia. The administrative center of the regency and the capital of the province is the independent municipality of Serang...
in Java. The areas of Banten
Banten
Banten is a province of Indonesia in Java. Formerly part of the Province of West Java, it was made a separate province in 2000.The administrative center is Serang. Preliminary results from the 2010 census counted some 10.6 million people.-Geography:...
on Java and the Lampung
Lampung
Lampung is a province of Indonesia. It is located on the southern tip of the island of Sumatra and borders the provinces of Bengkulu and South Sumatra. Lampung is the original home of the Lampung people, who speak a distinct language from other people in Sumatra and have their own alphabet. Its...
on Sumatra
Sumatra
Sumatra is an island in western Indonesia, westernmost of the Sunda Islands. It is the largest island entirely in Indonesia , and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538...
were devastated. There are numerous documented reports of groups of human skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
s floating across the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
on rafts of volcanic pumice
Pumice
Pumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid...
and washing up on the east coast of Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, up to a year after the eruption. Some land on Java was never repopulated; it reverted to jungle
Jungle
A Jungle is an area of land in the tropics overgrown with dense vegetation.The word jungle originates from the Sanskrit word jangala which referred to uncultivated land. Although the Sanskrit word refers to "dry land", it has been suggested that an Anglo-Indian interpretation led to its...
and is now the Ujung Kulon National Park
Ujung Kulon National Park
Ujung Kulon National Park is located at the western-most tip of Java, Banten, Indonesia. It includes the volcanic island group of Krakatoa and other islands including Panaitan, Handeuleum and Peucang on the Sunda Strait.-Geography:...
.
Tsunamis and distant effects
Ships as far away as South AfricaSouth Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
rocked as tsunamis hit them, and the bodies of victims were found floating in the ocean for weeks after the event. The tsunamis which accompanied the eruption are believed to have been caused by gigantic pyroclastic flow
Pyroclastic flow
A pyroclastic flow is a fast-moving current of superheated gas and rock , which reaches speeds moving away from a volcano of up to 700 km/h . The flows normally hug the ground and travel downhill, or spread laterally under gravity...
s entering the sea; each of the four great explosions was accompanied by a massive pyroclastic flow resulting from the gravitational collapse of the eruption column. This caused several cubic kilometers of material to enter the sea, displacing an equally huge volume of seawater. The town of Merak was destroyed by a tsunami 46 m (150.9 ft) high. Some of the pyroclastic flows reached the Sumatran coast as much as 40 km (24.9 mi) away, having apparently moved across the water on a "cushion" of superheated steam. There are also indications of submarine pyroclastic flows reaching 15 km (9.3 mi) from the volcano.
A recent documentary film showed tests made by a research team at the University of Kiel
University of Kiel
The University of Kiel is a university in the city of Kiel, Germany. It was founded in 1665 as the Academia Holsatorum Chiloniensis by Christian Albert, Duke of Holstein-Gottorp and has approximately 23,000 students today...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, of pyroclastic flows moving over water. The tests revealed that hot ash travelled over the water on a cloud of superheated steam, continuing to be a pyroclastic flow after crossing water; the heavy matter precipitated out of the flow shortly after initial contact with the water, creating a tsunami due to the precipitate mass.
Smaller waves were recorded on tidal gauges as far away as the English Channel
English Channel
The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...
. These occurred too soon to be remnants of the initial tsunamis, and may have been caused by concussive air waves from the eruption. These air waves circled the globe several times and were still detectable using barograph
Barograph
A barograph is a recording aneroid barometer. It produces a paper or foil chart called a barogram that records the barometric pressure over time....
s five days later.
Geographic effects
In the aftermath of the eruption, it was found that the island of Krakatoa had almost entirely disappeared, except for the southern half of Rakata cone cut off along a vertical cliff, leaving behind a 250 metres (820.2 ft) deep calderaCaldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
. Of the northern two-thirds of the island, only a rocky islet named Bootsmansrots ('Bosun's Rock', a fragment of Danan) was left; Poolsche Hoed
Poolsche Hoed
Poolsche Hoed was a small rocky islet between Krakatoa and Lang Island in the Sunda Strait. It disappeared in the 1883 eruption of Krakatoa....
had disappeared.
As a result of the huge amount of material deposited by the volcano, the surrounding ocean floor was drastically altered. It is estimated that as much as 18 cubic kilometre of ignimbrite
Ignimbrite
An ignimbrite is the deposit of a pyroclastic density current, or pyroclastic flow, a hot suspension of particles and gases that flows rapidly from a volcano, driven by a greater density than the surrounding atmosphere....
was deposited over an area of 1100000 km² (424,712.4 sq mi), largely filling the 30 metre deep basin around the mountain. The land masses of Verlaten and Lang were increased, as was the western part of the remnant of Rakata. Much of this gained material quickly eroded away, but volcanic ash continues to be a significant part of the geological composition of these islands.
Two nearby sandbanks (called Steers
Steers (island)
Steers was an island in the Sunda Strait between Java and Sumatra. It, and a neighboring island Calmeyer, were created from volcanic products from the 1883 eruption of Krakatoa, in the Sebesi Channel between Krakatoa and Sebesi, which was a fairly shallow area .Steers was the slightly larger of the...
and Calmeyer
Calmeyer
Calmeyer was an island in the Sunda Strait between Java and Sumatra. It, and a neighboring island Steers , were created from volcanic products from the 1883 eruption of Krakatoa, in the Sebesi Channel between Krakatoa and Sebesi, which was a fairly shallow area .Calmeyer was somewhat higher than...
after the two naval officers who investigated them) were built up into islands by ashfall, but the sea later washed them away. Seawater on hot volcanic deposits on Steers and Calmeyer caused steam which some people mistook for continued eruption.
Global climate
In the year following the eruption, average global temperatures fell by as much as 1.2 C-change. Weather patterns continued to be chaotic for years, and temperatures did not return to normal until 1888. The eruption injected an unusually large amount of sulfur dioxideSulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
(SO2) gas high into the stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
which was subsequently transported by high-level winds all over the planet. This led to a global increase in sulfurous acid
Sulfurous acid
Sulfurous acid is the chemical compound with the formula H2SO3. There is no evidence that sulfurous acid exists in solution, but the molecule has been detected in the gas phase...
(H2SO3) concentration in high-level cirrus cloud
Cirrus cloud
Cirrus clouds are atmospheric clouds generally characterized by thin, wispy strands, giving them their name from the Latin word cirrus meaning a ringlet or curling lock of hair...
s. The resulting increase in cloud reflectivity
Reflectivity
In optics and photometry, reflectivity is the fraction of incident radiation reflected by a surface. In general it must be treated as a directional property that is a function of the reflected direction, the incident direction, and the incident wavelength...
(or albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
) would reflect more incoming light from the sun than usual, and cool the entire planet until the suspended sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
fell to the ground as acid precipitation.
Global optical effects
The eruption darkened the sky worldwide for years afterwards, and produced spectacular sunsets throughout the world for many months. British artist William AshcroftWilliam Ashcroft
William Ashcroft was a late 19th Century British artist best known for his color sketches of sunsets over England in the years after the 1883 explosion of the Krakatoa volcano, recording details otherwise unavailable before the invention of color photography....
made thousands of colour sketches of the red sunsets half-way around the world from Krakatoa in the years after the eruption.
In 2004, an astronomer proposed the idea that the blood-red sky shown in Edvard Munch
Edvard Munch
Edvard Munch was a Norwegian Symbolist painter, printmaker and an important forerunner of expressionist art. His best-known composition, The Scream, is part of a series The Frieze of Life, in which Munch explored the themes of love, fear, death, melancholia, and anxiety.- Childhood :Edvard Munch...
's famous 1893 painting The Scream
The Scream
Scream is the title of Expressionist paintings and prints in a series by Norwegian artist Edvard Munch, showing an agonized figure against a blood red sky...
is also an accurate depiction of the sky over Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
after the eruption. This explanation has been disputed by art scholars who note that Munch was an expressive rather than descriptive painter.
Weather watchers of the time tracked and mapped the effects on the sky. They labeled the phenomenon the "equatorial smoke stream". This was the first identification of what is known today as the Jet stream
Jet stream
Jet streams are fast flowing, narrow air currents found in the atmospheres of some planets, including Earth. The main jet streams are located near the tropopause, the transition between the troposphere and the stratosphere . The major jet streams on Earth are westerly winds...
.
This eruption also produced a Bishop's Ring
Bishop's Ring
A Bishop's Ring is a diffuse brown or bluish halo observed around the sun. It is typically observed after large volcanic eruptions. The first recorded observation of a Bishop's Ring was by Rev. S. Bishop of Honolulu, after the Krakatoa eruption of 1883....
around the sun by day, and a volcanic purple light at twilight.
Possible causes
The fate of Krakatoa itself has been the subject of some dispute among geologists. It was originally proposed that the island had been blown apart by the force of the eruption. However, most of the material deposited by the volcano is clearly magmatic in origin and the caldera formed by the eruption is not extensively filled with deposits from the 1883 eruption. This indicates that the island subsided into an empty magma chamberMagma chamber
A magma chamber is a large underground pool of molten rock found beneath the surface of the Earth. The molten rock in such a chamber is under great pressure, and given enough time, that pressure can gradually fracture the rock around it creating outlets for the magma...
at the end of the eruption sequence, rather than having been destroyed during the eruptions.
The main theories are:
- Contemporary investigators believed that the volcano's vents had sunk below sea level on the morning of 27 August, letting seawater flood into it and causing a massive series of phreaticPhreaticThe term phreatic is used in Earth sciences to refer to matters relating to ground water below the water table . The term 'phreatic surface' indicates the location where the pore water pressure is under atmospheric conditions...
(interaction of ground water and magma) explosions. - The seawater could have chilled the magmaMagmaMagma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
, causing it to crust over and producing a "pressure cooker" effect relieved only when explosive pressures were reached.
Both these ideas assumed that the island subsided before the explosions; however, the evidence does not support that conclusion and the pumice and ignimbrite deposits are not of a kind consistent with a magma-seawater interaction.
- A massive underwater land slump or partial subsidence suddenly left the highly pressurized magma chamber wide open.
- The final explosions may have been caused by magma mixing caused by a sudden infusion of hot basaltic magma into the cooler and lighter magma in the chamber below the volcano. This would have resulted in a rapid and unsustainable increase in pressure, leading to a cataclysmic explosion. Evidence for this theory is the existence of pumice consisting of light and dark material, the dark material being of much hotter origin. However, such material reportedly is less than 5% of the content of the Krakatoa ignimbriteIgnimbriteAn ignimbrite is the deposit of a pyroclastic density current, or pyroclastic flow, a hot suspension of particles and gases that flows rapidly from a volcano, driven by a greater density than the surrounding atmosphere....
and some investigators have rejected this as a prime cause of the 27 August explosions.
Verbeek investigation
Although the violent engulfment phase of the eruption was over by late afternoon of August 27, after light returned by the 29th, reports continued for months that Krakatoa was still in eruption. One of the earliest duties of Verbeek's committee was to determine if this was true and also verify reports of other volcanoes erupting on Java and Sumatra. In general, these were found to be false, and Verbeek discounted any claims of Krakatoa still erupting after mid-October as due to steaming of hot material, landslides due to heavy monsoon rains that season, and "hallucinations due to electrical activity" seen from a distance.No signs of activity were seen in the next several years until 1913, when an eruption was reported. Investigation could find no evidence the volcano was awakening, and it was determined that what had been mistaken for renewed activity had actually been a major landslide (possibly the one which formed the second arc to Rakata's cliff).
Examinations after 1930 of bathymetric charts made in 1919 show evidence of a bulge indicative of magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
near the surface at the site that became Anak Krakatau.
See also
- Krakatoa documentary and historical materialsKrakatoa documentary and historical materialsKrakatoa in the Sunda Strait in Indonesia has attracted a significant literaure and media response to the 1883 eruption.-Books:* Alfred, E. & Seward, A.C., The New Flora of the Volcanic Island of Krakatau, * Rogier Verbeek's initial report on the eruption ran in Nature in May 1884...
- Krakatoa in media and popular cultureKrakatoa in media and popular cultureThe 1883 eruption of Krakatoa, a volcanic island in the Sunda Strait in Indonesia, has inspired several books and films...
- List of deadliest natural disasters
- List of volcanoes in Indonesia
- Phreatic eruptionPhreatic eruptionA phreatic eruption, also called a phreatic explosion or ultravulcanian eruption, occurs when rising magma makes contact with ground or surface water. The extreme temperature of the magma causes near-instantaneous evaporation to steam, resulting in an explosion of steam, water, ash, rock, and...
- San Benedicto IslandSan Benedicto IslandSan Benedicto, formerly Santo Tomás, is an uninhabited island, and third largest island of the Revillagigedo Islands, located in the Pacific at ....
- Volcanic Explosivity IndexVolcanic Explosivity IndexThe Volcanic Explosivity Index was devised by Chris Newhall of the U.S. Geological Survey and Stephen Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions....
(includes list of large eruptions)
External links
- "In het Rijk van Vulcaan"—"In the Realm of the Volcano", eye witness account by R.A. van Sandick (in Dutch).
- 1883 Eruption of Krakatau from the United States Geological SurveyUnited States Geological SurveyThe United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...
's Cascades Volcano Observatory. - Krakatau, Indonesia (1883) information from San Diego State UniversitySan Diego State UniversitySan Diego State University , founded in 1897 as San Diego Normal School, is the largest and oldest higher education facility in the greater San Diego area , and is part of the California State University system...
about the 1883 eruption. - Krakatoa Volcano: The Son Also Rises—Companion website to the NPR programme.
- On-line images of some of Ashcroft's sunset sketches.