Anak Krakatoa ( id, Anak Krakatau)
[English translation and common name: ''Child of Krakatoa''] is a
volcanic island
Geologically, a high island or volcanic island is an island of volcanic origin. The term can be used to distinguish such islands from low islands, which are formed from sedimentation or the uplifting of coral reefs (which have often formed ...
in
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
. On 29 December 1927, Anak Krakatoa first emerged from the caldera formed in 1883 by
the explosive volcanic eruption that destroyed the island of
Krakatoa
Krakatoa (), also transcribed (), is a caldera in the Sunda Strait between the islands of Java and Sumatra in the Indonesian province of Lampung. The caldera is part of a volcanic island group (Krakatoa archipelago) comprising four islands. Tw ...
. There has been sporadic eruptive activity at the site since the late 20th century, culminating with a large underwater collapse of the volcano that caused a deadly
Tsunami
A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explo ...
in December 2018. There has been subsequent activity since. Due to its young age, the island is one of several in the area that are of interest to, and the subject of extensive study by,
volcanologist
A volcanologist, or volcano scientist, is a geologist who focuses on understanding the formation and eruptive activity of volcanoes. Volcanologists frequently visit volcanoes, sometimes active ones, to observe and monitor volcanic eruptions, col ...
s.
History
Background
After the
cataclysmic eruption of Krakatoa in 1883, Krakatoa Island lost approximately two-thirds of its body on the northwest side, obliterating the peaks of Perbuwatan and Danan, and leaving only the southern half of the island, including the
Rakata
Rakata ( ), also called Greater Krakatau, is a partially collapsed stratovolcano on the Indonesian island of Krakatoa ( id, Krakatau) in the Sunda Strait between the islands of Sumatra and Java. Standing tall, it was the largest and southernmo ...
volcano, as the last remnant of the original island. The lost area became a shallow sea.
Regrowth
![COLLECTIE TROPENMUSEUM Het eiland Anak Krakatau gevormd na de eruptie van de Krakatau TMnr 10004045](https://upload.wikimedia.org/wikipedia/commons/a/ad/COLLECTIE_TROPENMUSEUM_Het_eiland_Anak_Krakatau_gevormd_na_de_eruptie_van_de_Krakatau_TMnr_10004045.jpg)
In early 1927 volcanic activity began to appear at the point located between where the former peaks of Mount
Perboewatan Perboewatan (also spelled Perbuatan; apparently a Malay word of uncertain derivation) was one of the three main volcanic cones (the others being Danan and Rakata) on the island of Krakatoa (or Krakatau), in the Sunda Strait, in Indonesia. It was ...
and Mount
Danan had been. This was a short-lived appearance of a small island that was sunk by sea waves within a week. Several months later, volcanic activity began to create a more permanent land formation
[Winchester, S. 2005. Krakatoa. The Day The World Exploded 27 August 1883. Penguin Books.] that, due to rain and waves, once again collapsed under the sea after its volcanic activity stopped. This process repeated several times during the next three years. On 11 August 1930, the volcanic island permanently rose above sea level, and was locally named ''Anak Krakatau'' (or "Child of Krakatoa"). It has been the site of repeated eruptive episodes ever since.
[''Wild Indonesia: The Birth of an Island'']
. PBS online books. Retrieved 27 December 2018. Anak Krakatoa's highest point increased at an average rate of 7–9 meters per year through September 2018.
Geography
Anak Krakatoa is located in the
Sunda Strait
The Sunda Strait ( id, Selat Sunda) is the strait between the Indonesian islands of Java island, Java and Sumatra. It connects the Java Sea with the Indian Ocean.
Etymology
The strait takes its name from the Sunda Kingdom, which ruled the weste ...
—between the islands of
Java
Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...
and
Sumatra
Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 473,481 km2 (182,812 mi.2), not including adjacent i ...
—in the Indonesian province of
Lampung
Lampung (Lampung: ), officially the Province of Lampung ( id, Provinsi Lampung) is a province of Indonesia. It is located on the southern tip of the island of Sumatra. It has a short border with the province of Bengkulu to the northwest, and a ...
.
The volcano is contained within the
Ujung Kulon National Park
Ujung Kulon National Park is at the westernmost tip of Java, in Banten province of Indonesia. It includes the volcanic island group of Krakatoa in Lampung province, and other islands including Panaitan, as well as smaller offshore islets such as ...
,
[A UNESCO World Heritage Property] and is part of the Pacific
Ring of Fire
The Ring of Fire (also known as the Pacific Ring of Fire, the Rim of Fire, the Girdle of Fire or the Circum-Pacific belt) is a region around much of the rim of the Pacific Ocean where many volcanic eruptions and earthquakes occur. The Ring o ...
.
[''Global Volcanism Program''](_blank)
Smithsonian Institution, National Museum of Natural History – Department of Mineral Sciences ; website; accessed June 2022
Geology
![Indonesia, Sunda Straits](https://upload.wikimedia.org/wikipedia/commons/4/4a/Indonesia%2C_Sunda_Straits.jpg)
The island is situated approximately north of the
Sunda Trench
The Sunda Trench, earlier known as and sometimes still indicated as the Java Trench, is an oceanic trench located in the Indian Ocean near Sumatra, formed where the Australian- Capricorn plates subduct under a part of the Eurasian Plate. It is l ...
marking the
subduction zone
Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...
separating the
Australian Plate
The Australian Plate is a major tectonic plate in the eastern and, largely, southern hemispheres. Originally a part of the ancient continent of Gondwana, Australia remained connected to India and Antarctica until approximately when India broke ...
and the fixed
Sunda Plate
The Sunda Plate is a minor tectonic plate straddling the Equator in the Eastern Hemisphere on which the majority of Southeast Asia is located.
The Sunda Plate was formerly considered a part of the Eurasian Plate, but the GPS measurements have ...
, atop an
oceanic crust
Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumu ...
of less than in thickness.
In geologic terms, it has recently formed within the
caldera
A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...
of the Krakatoa volcanic eruption. The entire island comprises a
Somma
A somma volcano (also known as a sommian) is a volcanic caldera that has been partially filled by a new central cone. The name comes from Mount Somma, a stratovolcano in southern Italy with a summit caldera in which the upper cone of Mount Ves ...
-
stratovolcano
A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and per ...
system of the late
Holocene epoch
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...
, and features a
pyroclastic cone
Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and s ...
. The major rock-type components of Anak Krakatoa include
Andesite
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomi ...
,
Dacite
Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...
, and
Basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
; with minor indications of
Trachyte
Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and al ...
.
The island had reached a maximum elevation of before its collapse during the 2018 eruptive event.
Volcanic activity
The volcano's most recent eruptive episode began in 1994. Quiet periods of a few days have alternated with almost continuous
Strombolian eruptions since then. Hot gases, rocks, and lava were released in an eruption in April 2008. Scientists monitoring the volcano warned people to stay out of a zone around the island.
On 6 May 2009, the
Volcanological Survey of Indonesia Volcanological Survey of Indonesia is the official Indonesian government agency under Ministry of Energy and Mineral Resources which are responsible for investigating, recording, and warning about volcanoes within the Indonesian region of responsibi ...
raised the eruption alert status of Anak Krakatoa to Level 3. An expedition to the volcano revealed that a wide
lava dome
In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on ...
was growing in its crater. In January 2012, volcanologists at the
University of Oregon
The University of Oregon (UO, U of O or Oregon) is a public research university in Eugene, Oregon. Founded in 1876, the institution is well known for its strong ties to the sports apparel and marketing firm Nike, Inc, and its co-founder, billion ...
warned that a tsunami caused by flank collapse of Anak Krakatoa was likely, as it had formed on the steep eastern slope of the large caldera formed by the 1883 explosive eruption.
2018 eruption and aftermath
A new eruptive phase was observed starting in June 2018; and on 15 October 2018, Anak Krakatau had a strong
Strombolian to weak
Vulcanian eruption
A Vulcanian eruption is a type of volcanic eruption characterized by a dense cloud of ash-laden gas exploding from the crater and rising high above the peak. They usually commence with phreatomagmatic eruptions which can be extremely noisy due t ...
that sent lava bombs into the water.
An eruption of the volcano on 22 December 2018 caused a deadly tsunami, with waves up to five meters in height making landfall.
On 31 December 2018, the disaster agency stated the tsunami's death toll was 437, with 14,059 injured.
The tsunami affected more than 300 kilometers (186 mi) of coastline in Sumatra and Java and 40,000 people were displaced.
This made the eruption the
second deadliest volcanic eruption of the 21st century to date. Cone collapse—with tsunami generation—was considered a potential hazard immediately before the eruption.
Scientists had modeled the possibility six years before the event, and had identified the western flank as the section of the volcano most likely to fail.
![Anak Krakatoa on Sentinel-2 L2A image 2022 May 03](https://upload.wikimedia.org/wikipedia/commons/1/1a/Anak_Krakatoa_on_Sentinel-2_L2A_image_2022_May_03.jpg)
Following the December 2018 eruption, it was believed that the southwest sector of the volcano, including the summit, had collapsed during the eruption, triggering the tsunami. On 23 December, this was confirmed by satellite data and helicopter footage, with the main conduit seen erupting from underwater, producing
Surtseyan-style activity. The volcano lost over two-thirds of its volume due to this event, and its
elevation
The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § Vert ...
above sea level was reduced from to just .
Satellite radar observations showed that by 10 January 2019, the volcano had continued to form, with further eruptions beginning to re-model the remnant structure. The crater, which had become open to the sea immediately after the eruption, had a complete rim above sea level. In May 2019,
phreatomagmatic
Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions cont ...
activity was observed around the newly reconstructed crater as the volcano continued to increase in height and remodel the areas destroyed in 2018.
2020 eruption
Anak Krakatoa began erupting again on the morning of 10 April 2020. The first eruption could be heard in the Indonesian capital of
Jakarta
Jakarta (; , bew, Jakarte), officially the Special Capital Region of Jakarta ( id, Daerah Khusus Ibukota Jakarta) is the capital and largest city of Indonesia. Lying on the northwest coast of Java, the world's most populous island, Jakarta ...
, over away, and was spewing out a high column of ash and smoke according to the Center for Volcanology and Geological Disaster Mitigation's (PVMBG) magma volcanic activity report, which also said that the first eruption lasted one minute and 12 seconds starting at 9:58 p.m. The eruption spewed ash to about and a secondary ash plume made it to about . The eruption was largely magmatic with lava fountains visible. No widespread damage was reported, and the eruption ended several hours later.
2022 eruption
Anak Krakatoa presented a minor eruption on 4 to 5 February 2022. At 8:20 PM on 24 April 2022, Anak Krakatoa once again erupted, sending a massive plume of ash 3,157 metres (10,358 ft) above the sea level. The volcano had erupted 21 times in the first four months of 2022, with the 24 April eruption being the biggest. On 26 April,
Meteorology, Climatology, and Geophysical Agency
Meteorology, Climatology, and Geophysical Agency ( id, Badan Meteorologi, Klimatologi, dan Geofisika, abbreviated BMKG) is an Indonesian non-departmental government agency for meteorology, climatology, and geophysics.
History
Its history began ...
(BMKG) increased the alert level for Anak Krakatoa from level 2 to level 3. The agency warned of possible high waves and tsunami following any eruptive event.
See also
*
Krakatoa documentary and historical materials Krakatoa, in the Sunda Strait in Indonesia, has attracted a significant literature and media response to the 1883 eruption of Krakatoa, 1883 eruption and subsequent events in the vicinity.
Nonfiction
Books
* Alfred, E. & Seward, A.C., ''The New Fl ...
*
List of volcanic eruptions by death toll
Volcanic eruptions can be highly explosive. Some volcanoes have undergone catastrophic eruptions, killing large numbers of humans or other life forms. This list documents volcanic eruptions by human death toll.
Volcanic eruptions
See also
* ...
*
List of volcanoes in Indonesia
The geography of Indonesia is dominated by volcanoes that are formed due to subduction zones between the Eurasian plate and the Indo-Australian plate. Some of the volcanoes are notable for their eruptions, for instance, Krakatoa for its globa ...
Notes
References
External links
*
{{DEFAULTSORT:Anak Krakatoa
Lampung
Krakatoa
Active volcanoes of Indonesia
Mountains of Indonesia
Subduction volcanoes
Submarine calderas
Islands of the Sunda Strait
Uninhabited islands of Indonesia
New islands
Calderas of Indonesia