Anak Krakatoa Explained

Anak Krakatoa
Photo Alt:Aerial view of volcanic island with another, rocky island in the background
Location:Sunda Strait
Lampung, Indonesia
Map:Indonesia
Map Relief:1
Coordinates:-6.102°N 105.423°W
Elevation:
    Listing:Spesial Ribu
    Type:Somma-stratovolcano
    Age:Holocene – very recent
    Last Eruption:24 April 2022 (Ongoing)

    Anak Krakatoa (Indonesian: Anak Krakatau)[1] is a volcanic island in Indonesia. 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. There has been sporadic eruptive activity at the site since the late 20th century, culminating in a large underwater collapse of the volcano, which caused a deadly tsunami in December 2018. There has been subsequent activity since. Owing 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 volcanologists.

    History

    Background

    After the cataclysmic eruption of Krakatoa in 1883, Krakatoa Island lost approximately two-thirds of its mass on the northwest side, obliterating the peaks of Perboewatan and Danan, and leaving only the southern half of the island, including the Rakata volcano, as the last remnant of the original island. The lost area became a shallow sea.

    Regrowth

    In early 1927 volcanic activity began to appear at the point located between where the former peaks of Mount Perboewatan and Mount Danan had been.[2] This was a short-lived appearance of a small island that was sunk by sea waves within a week.[3] Several months later volcanic activity began to create a more permanent land formation[4] which, owing to rain and waves, once again collapsed under the sea after its volcanic activity stopped. This process recurred 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 (Child of Krakatoa).[5] It has been the site of repeated eruptive episodes ever since.[6] [7] Anak Krakatoa's highest point increased at an average rate of 7–9 meters per year through September 2018.[8]

    Geography

    Anak Krakatoa is located in the Sunda Strait—between the islands of Java and Sumatra—in the Indonesian province of Lampung.[9] The volcano is contained within the Ujung Kulon National Park,[10] and is part of the Pacific Ring of Fire.[11]

    Geology

    The island is situated approximately north of the Sunda Trench marking the subduction zone separating the Australian Plate and the fixed Sunda Plate, atop an oceanic crust of less than in thickness. In geologic terms, it has recently formed within the caldera of the Krakatoa volcanic eruption. The entire island comprises a Somma-stratovolcano system of the late Holocene epoch, and features a pyroclastic cone. The major rock-type components of Anak Krakatoa include andesite, dacite, and basalt; with minor indications of trachyte.

    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 3km (02miles) zone around the island.[12]

    On 6 May 2009, the Volcanological Survey of Indonesia raised the eruption alert status of Anak Krakatoa to Level 3.[13] An expedition to the volcano revealed that a 100abbr=onNaNabbr=on wide lava dome was growing in its crater. In January 2012, volcanologists at the University of Oregon 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.[14]

    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 that sent lava bombs into the water.[15] [16]

    An eruption of the volcano on 22 December 2018 caused a deadly tsunami, with waves up to five meters in height making landfall.[17] [18] On 31 December 2018, the disaster agency stated the tsunami's death toll was 437, with 14,059 injured.[19] The tsunami affected more than 300 kilometers (186 mi) of coastline in Sumatra and Java and 40,000 people were displaced.[20] 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.[18] 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.[18]

    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.[21] The volcano lost over two-thirds of its volume due to this event,[22] and its elevation above sea level was reduced from to just .[23] [18]

    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.[24] In May 2019, phreatomagmatic activity was observed around the newly reconstructed crater as the volcano continued to increase in height and remodel the areas destroyed in 2018.[25]

    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, over 150km (90miles) away, and was spewing out a 200m (700feet) 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.[26] The eruption spewed ash to about 14km (09miles) and a secondary ash plume made it to about 11km (07miles). The eruption was largely magmatic with lava fountains visible. No widespread damage was reported, and the eruption ended several hours later.[27]

    2022 eruption

    Anak Krakatoa presented a minor eruption on 4 to 5 February 2022.[28] [29] 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.[30] On 26 April, Meteorology, Climatology, and Geophysical Agency (BMKG) increased the alert level for Anak Krakatoa from level 2 to level 3.[31] The agency warned of possible high waves and tsunami following any eruptive event.[32]

    2023 eruption

    Anak Krakatoa began another eruption cycle on 15 September 2023,[33] [29] with white gas-and-steam plumes as high as 100 m above Krakatau’s summit on most days during 15–21 September and drifting NW, N and NE. White-and-gray plumes rose as high as 100 m and drifted NW on 21 November. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay at least 5 km away from the crater.

    See also

    Notes and References

    1. English translation and common name: Child of Krakatoa
    2. Web site: Krakatau Volcano . live . https://web.archive.org/web/20220428011449/https://www.volcanodiscovery.com/krakatau.html . 28 April 2022 . 5 May 2022 . www.volcanodiscovery.com.
    3. Web site: Mary Bagley . 15 September 2017 . Krakatoa Volcano: Facts About 1883 Eruption . 6 May 2022 . livescience.com . en . 4 May 2022 . https://web.archive.org/web/20220504213812/https://www.livescience.com/28186-krakatoa.html . live .
    4. Winchester, S. 2005. Krakatoa. The Day The World Exploded 27 August 1883. Penguin Books.
    5. Gardner. Màiri F.. Troll. Valentin R.. Gamble. John A.. Gertisser. Ralf. Hart. Garret L.. Ellam. Rob M.. Harris. Chris. Wolff. John A.. 1 January 2013. Crustal Differentiation Processes at Krakatau Volcano, Indonesia. Journal of Petrology. en. 54. 1. 149–182. 10.1093/petrology/egs066. 0022-3530. free. 30 September 2020. 5 January 2022. https://web.archive.org/web/20220105152821/https://academic.oup.com/petrology/article/54/1/149/1443885. live.
    6. Dahren. Börje. Troll. Valentin R.. Andersson. Ulf B.. Chadwick. Jane P.. Gardner. Màiri F.. Jaxybulatov. Kairly. Koulakov. Ivan. 1 April 2012. Magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions. Contributions to Mineralogy and Petrology. en. 163. 4. 631–651. 10.1007/s00410-011-0690-8. 2012CoMP..163..631D. 52064179. 1432-0967. 4 February 2021. 18 January 2022. https://web.archive.org/web/20220118054649/https://link.springer.com/article/10.1007%2Fs00410-011-0690-8. live.
    7. https://www.pbs.org/wildindonesia/island/index.html Wild Indonesia: The Birth of an Island
    8. Web site: Geologi . Pusat Vulkanologi dan Mitigasi Bencana . 27 December 2018 . Pers Rilis Peningkatan Status G. Anak Krakatau Kamis 27 Desember 2018 . Press Releases Status Improvement of G. Anak Krakatau Thursday 27 December 2018 . https://web.archive.org/web/20181227222741/https://magma.vsi.esdm.go.id/press/view.php?id=172 . 27 December 2018 . 2022-05-06 . MAGMA Indonesia . id.
    9. 262000 . Krakatoa. 6 January 2021.
    10. A UNESCO World Heritage Property
    11. https://volcano.si.edu/volcano.cfm?vn=262000 Global Volcanism Program
    12. News: Supriyatin . 11 November 2007 . Indonesia's Krakatau roars, dazzles with fireworks . Reuters India . live . 10 January 2019 . https://web.archive.org/web/20090110081917/http://in.reuters.com/article/worldNews/idINIndia-30436520071111?sp=true . 10 January 2009.
    13. Web site: Status G. Anak Krakatau dinaikkan menjadi Siaga (Level III) . Anak Krakatau's status raised to Alert (Level III) . https://web.archive.org/web/20090506120112/http://portal.vsi.esdm.go.id/joomla/ . 6 May 2009 . 20 March 2012 . . Indonesian.
    14. Giachetti . T. . Paris . R. . Kelfoun . K. . Ontowirjo . B. . Terry . J. P. . Goff . J. . Tsunami Hazard Related to a Flank Collapse of Anak Krakatau Volcano, Sunda Strait, Indonesia . Natural Hazards in the Asia–Pacific Region: Recent Advances and Emerging Concepts . January 2012 . 361 . 79–90 . 10.1144/SP361.7 . Special Publications . 1 . Geological Society . London . 2012GSLSP.361...79G . 131173974 . 0305-8719 . 15 January 2019 . 25 July 2019 . https://web.archive.org/web/20190725231808/https://sp.lyellcollection.org/content/361/1/79 . live .
    15. Web site: 20 October 2018 . Krakatau volcano (Indonesia): vulcanian explosions - field report 13-19 Oct 2018 . live . https://web.archive.org/web/20200718063839/https://www.volcanodiscovery.com/krakatau/news/71210/Krakatau-volcano-Indonesia-vulcanian-explosions-field-report-13-19-Oct-2018.html . 18 July 2020 . 4 May 2022 . www.volcanodiscovery.com . Volcano Discovery . en.
    16. Web site: Sennert . Sally Kuhn . Global Volcanism Program Report on Krakatau (Indonesia) — 20–26 June 2018 . live . https://web.archive.org/web/20210519031129/https://volcano.si.edu/ShowReport.cfm?doi=10.5479%2Fsi.GVP.WVAR20180620-262000 . 19 May 2021 . 4 May 2022 . volcano.si.edu . 10.5479/si.GVP.WVAR20180620-262000 . 31 January 2024 . en.
    17. Web site: Indonesia tsunami: At least 222 Dead and 843 injured after Anak Krakatau volcano erupts. 23 December 2018. telegraph.co.uk. 23 December 2018. 16 August 2019. https://web.archive.org/web/20190816002254/https://www.telegraph.co.uk/news/2018/12/22/indonesia-tsunami-least-20-dead-165-injured-waves-hit-beaches/. live.
    18. News: Amos . Jonathan . 29 December 2018 . Anak Krakatau: Indonesian Volcano's Dramatic Collapse . en-GB . BBC News . 4 May 2022 . https://web.archive.org/web/20200202125257/https://www.bbc.com/news/science-environment-46707731 . 2 February 2020.
    19. Web site: 31 December 2022 . Number of injured in Indonesia tsunami surges to over 14,000 . subscription . live . https://web.archive.org/web/20190729132342/https://www.thestar.com.my/news/regional/2018/12/31/number-of-injured-in-indonesia-tsunami-surges-to-over-14000/ . 29 July 2019 . 31 December 2018 . The Star Online . Asean Plus.
    20. Web site: Associated Press . 29 December 2022 . Volcano that triggered tsunami now a quarter of its pre-eruption size . https://web.archive.org/web/20191012065958/https://www.nbcnews.com/news/world/indonesia-s-anak-krakatau-volcano-triggered-deadly-tsunami-now-quarter-n952906 . 12 October 2019 . 4 May 2022 . NBC News . en.
    21. Web site: 22-23 Dec 2018 Eruption & Tsunami of Krakatoa - Updates . . 25 December 2018 . 26 December 2018 . 9 June 2019 . https://web.archive.org/web/20190609182341/https://www.volcanodiscovery.com/krakatoa/2018/dec/eruption-tsunami/updates.html . live .
    22. Walter. Thomas R.. Haghshenas Haghighi. Mahmud. Schneider. Felix M.. Coppola. Diego. Motagh. Mahdi. Saul. Joachim. Babeyko. Andrey. Dahm. Torsten. Troll. Valentin R.. Tilmann. Frederik. Heimann. Sebastian. 1 October 2019. Complex hazard cascade culminating in the Anak Krakatau sector collapse. Nature Communications. en. 10. 1. 4339. 10.1038/s41467-019-12284-5. 31575866. 6773710. 2019NatCo..10.4339W . 2041-1723. free.
    23. News: Indonesian volcano's lost stature . Amos . Jonathan . 29 December 2018 . BBC News . 29 December 2018 . en-GB . 2 February 2020 . https://web.archive.org/web/20200202125257/https://www.bbc.com/news/science-environment-46707731 . live .
    24. Web site: Amos . Jonathan . 10 January 2019 . Anak Krakatau: Finnish radar satellite eyes tsunami volcano . live . https://web.archive.org/web/20190526154647/https://www.bbc.co.uk/news/science-environment-46825354 . 26 May 2019 . 10 January 2019 . BBC News.
    25. Web site: 25 May 2019 . Krakatau volcano (Indonesia) activity update and field report: increasing unrest . live . https://web.archive.org/web/20190525121110/https://www.volcanodiscovery.com/krakatau/news/80657/Krakatau-volcano-Indonesia-activity-update-and-field-report-increasing-unrest.html . 25 May 2019 . 12 June 2019 . www.volcanodiscovery.com . Volcano Discovery.
    26. News: Fiqih . Moch . Prawira . Adjie . Dipa . Arya . 11 April 2020 . Anak Krakatau erupts, loud rumble heard in virus-stricken Greater Jakarta . The Jakarta Post . live . 6 January 2021 . https://web.archive.org/web/20200414022932/https://www.thejakartapost.com/news/2020/04/11/anak-krakatau-erupts-loud-rumble-heard-in-virus-stricken-greater-jakarta.html . 14 April 2020.
    27. News: Dan Satherley . 11 April 2020 . Eruption at Indonesian volcano Krakatoa . Newshub . live . 11 April 2020 . https://web.archive.org/web/20200411020901/https://www.newshub.co.nz/home/world/2020/04/massive-eruption-at-indonesian-volcano-krakatoa-report.html . 11 April 2020.
    28. Web site: 5 February 2022. Indonesia's Anak Krakatoa Spews Ash 1,500 Metres High. 5 February 2022. South China Morning Post. en. 5 February 2022. https://web.archive.org/web/20220205120317/https://www.scmp.com/news/asia/southeast-asia/article/3165951/indonesias-anak-krakatoa-volcano-spews-ash-1500-metres-sky. live.
    29. Indonesian Geological Agency
    30. Web site: Anak Krakatau volcano erupts, spews huge ash tower . 27 April 2022 . The Jakarta Post . en . 27 April 2022 . https://web.archive.org/web/20220427114343/https://www.thejakartapost.com/indonesia/2022/04/25/anak-krakatau-volcano-erupts-spews-huge-ash-tower.html . live .
    31. Web site: Sennert . Sally Kuhn . Global Volcanism Program Report on Krakatau (Indonesia) — 20–26 April 2022 . live . https://web.archive.org/web/20220504091033/https://volcano.si.edu/ShowReport.cfm?doi=10.5479%2Fsi.GVP.WVAR20220420-262000 . 4 May 2022 . 4 May 2022 . volcano.si.edu . Global Volcanism Program Smithsonian Institution . 10.5479/si.GVP.WVAR20220420-262000 . 31 January 2024 . en.
    32. Web site: 26 April 2022 . BMKG Warns of Possible Tsunami as 'Child of Krakatoa' Alert Level Raised Coconuts . live . https://web.archive.org/web/20220427015333/https://coconuts.co/jakarta/news/bmkg-warns-of-possible-tsunami-as-child-of-krakatoa-alert-level-raised/ . 27 April 2022 . 27 April 2022 . Coconuts Jakarta . en-US.
    33. Web site: 27 November 2023. Overall Green alert Volcanic eruption for Krakatau. 28 November 2023. Global Disaster Alert and Coordination System. en.

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