Mount Krakatau and Its Eruption History

 

Mount Krakatau is known in history when there was a major eruption in 416 BC, which caused a tsunami and the formation of a caldera (Judd, 1889), then De Neve (1981) obtained information that before the second paroxysmal occurred, several eruptions occurred in the 3rd, 9th, 10th centuries. , 11, 12, 14, 16 and 17 followed by the growth of Rakata, Danan and Action cones. The volcanic activity stopped in 1681.

The Krakatau complex consists of four islands, Rakata, Sertung, Panjang and Anak Krakatau. The first three islands are remnants of the caldera formation, while Anak Krakatau grew from January 20, 1930.

The paroxysmal eruption on 27 August 1883 is considered the largest event in its eruptive history, ejecting volcanic spices with a volume of 18 km3, smoke heights of 80 km and causing a tidal wave (tsunami) as high as 30 m along the west coast of Banten and the south coast of Lampung. Although there are no big cities along the coast as of now, 297 small towns (subdistrict cities) were destroyed by the tsunami and killed 36,417 people. An estimated 2000 people were killed in southern Sumatra by "hot ash" and there is clear evidence that pyroclastics reached that distance. 3150 people died in this pyroclastic direction, on the islands between Krakatau and Sumatra.

After resting lk. 200 years, Krakatau again shows its activities which began with several eruptions of Mount Danan and Mount Perbuatan. On May 20, 1883 the eruption of Mt. Basaltic composition initiated a paroxysmal eruption on August 27, 1883 which had dacite composition (SiO2 = 64-68%) (Neumann van Padang, 1951). The paroxysmal eruption occurred on Sunday 27 August 1883 at 04.00-06.41 and 10.00 local time. The sound of the eruption was heard as far as 4,500 km, the smoke height was 80 km, the energy released was 1 X 1025 erg. The tsunami occurred 30 minutes after the cataclysmic eruption with a wave height of 30 m on the west coast of Banten and the south coast of Lampung.

Krakatau calmed down again from February 1884 to June 1927, when on June 11, 1927 an eruption consisting of alkaline magma appeared at the center of the Krakatau complex, which was declared the birth of Mount Anak Krakatau. As a result of its eruptions, Mount Anak Krakatau grew bigger and taller, forming a cone which now reaches a height of lk. 300 m from sea level. In addition to increasing the height of the cone of its body, it also expands its land area.

Historical records of volcanic activity of Mount Anak Krakatau since its birth on June 11, 1930 to 2000, have erupted more than 100 times, both explosively and effusively. From a number of these eruptions, in general, the point of eruption is always moving around the body of the cone. Rest periods range from 1 - 8 years and generally occur every 4 years in the form of ash eruptions and lava flows. The last activity of Mount Anak Krakatau, namely the eruption of ash and lava flows, continued from November 8, 1992 until June 2000. The number of eruptions per day was recorded by a sessimograph placed at the Pasauran PGA Post, while the amount of volcanic material released during the eruption was lk. 13 million m3, consisting of lava and loose material of basaltic andesite composition.

Table of volcanic activity of Mount Krakatau:

1680 - 1681	May 1680 to May 1681, eruption of ash accompanied by lava flows.
1883	May 20, 1883, the activity started from Mt. Actions, eruptions of ash and bursts of steam reached a height of 11 km and the sound of the boom was heard as far as 200 km. In June volcanic activity also occurred at Mount Danan. The paroxysm eruption occurred on August 26-28. After 13.00, 26 August several eruptions occurred and reached their peak on Sunday 27 August, at 10.02 and at 10.52 the boom was heard in Singapore and Australia. This eruption ejected pumice and ash reaching a height of 70-80 km, the deposits occupying an area of ​​827,000 km2. The collapse of this volcanic body caused a tsunami with an average wave height of 20 m sweeping the beaches in the Sunda Strait and northwest Java, and caused 36,417 deaths. September and October phreatic eruptions.
1884	February, the phreatic eruption was a continuation of October 1883
1898	-
1927	December 29, new volcanic activity occurred in the center of the caldera, northeast of the caldera base at a depth of 188 m and was declared the birth of Mount Anak Krakatau. This new crater is in line with the previous Danan and Action craters. The series of eruptive activities continued until 1930, as follows:
1928	5 February, 25 March, 2 June, 6-13 July, 25 August-4 September, 4-26 November, 11-20 December.
1929	12 January-18 February, 6-13 March, 8-20 June, 25 July-25 August, 19 September-7 October, 7-23 December.
1930	14-28 January, 10 March-5 April, 30 April-15 May, 2 June-15 August.
1931	There was a crater lake, ash eruptions reaching a height of 2400 m and side eruptions on 23-26 September, 5-7 November, 5-21 December.
1932	February 12-17 eruption continued from the previous year.
1933	Eruptions at the crater lake on January 16-25 May, 10-17 June, 5-6 July, 5 September-5 October, 10 November-6 December.
1934	Follow-up activities from the previous year on January 6-26, during March, May 5-12, June 7-9. During this period one of the eruptions reached a height of 6800 m.
1935	Ash and phreatic eruptions in the crater lake, the size of the crater lake reaches 275 X 250 m2, activities occur on January 4-14, February 6-6 May and May 25-12 July.
1936	The ash eruption on October 13 and during November the height of the ash column ranged from 100 - 300 m.
1937	Eruptions in the crater lake occurred on August 6-21 September the ash height was between 2000-2600 m, then on November 17-23 small eruptions in the new crater in the southwest.
1938	Ash eruptions and phreatic eruptions in the crater lake lasted until 1940. Activities occurred on 4 July-29 August, 12-14 September, 2 October, 7 November, 8-9 December.
1939	January 15-27, March 20, June 1-4 August, September 23-25, December 13 to
1940	January 9, February 3-10, March 1-15 May, and June 10-2 July. In June the height of the eruption reached 1000-4000 m.
1941	Eruption in crater lake on January 28-12 February
1942	Eruption in the crater lake on January 29-30.
1943	Eruption in crater lake.
1944	Eruption in crater lake.
1945	Eruption in crater lake.
1946	Eruptions at the crater lake on July 25 and during December.
1947	Eruptions at the crater lake during April.
1948	Eruption in crater lake.
1949	Eruption in the crater lake on May 12.
1950	Eruption in the crater lake on 3-7 July.
1952	Eruption in the crater lake on October 10-11, formed a new cone with a crater lake with a diameter of 440 m.
1953	Ash eruption in the crater lake on September 20-23, the height of the cone reaches 116 m.
1958	Eruption in crater lake, date unknown.
1959	Eruptions in the crater lake during June-July. Eruption activities consist of 4 phases: 1. Black ash eruption, 2. Ash and gas eruption with a smoke pillar as high as 500 m, 3. Ash eruption as high as 1000 - 1500 m, and 4. Black ash eruption.
1960	Further eruption activity from the previous year, occurred on January 12-13, the smoke height reached 1000 m.
1961	The date of the eruption is unknown, obliterating the crescent crater lake and lava flows filling the crater and the eastern crater rim.
1963	Lava flows through the sea through the southwest embankment of the crater and forms a fan.
1968	Phreatic eruptions during September.
1972 - 1973	Continuous ash eruptions reach a height of 1600 m. Eyewitnesses observed eruptions on June 26, December 21-22 and December 29, 1972. The eruption continued until January 1973 and ended with lava flowing to the south, southwest and west, penetrating the sea and expanding the land.
1975	Ash eruption during this year and ended with lava spewing to the west-northwest.
1979	The ash eruption is almost during this year and ends with the lava spewing to the southwest.
1981	The eruption of ash from February to July, and ended with lava flows to the south on top of the 1973-1973 lava.
1984	The ash eruption occurred in the middle of the year and the date is unknown.
1988	The ash eruption on March 16-18 formed a new crater on the southern slope and its activities ended with lava flows confined to the southern slope.
1992 - 2000	The ash eruption occurred on November 8, its activities began with an increase in volcanic seismicity since August. Eruption activities continued until 2000 every day or every few minutes, spewing ash with an average height of 400 - 800 m and spewing lava. Lava flows occurred in November-December 1992, February 1993, April-May 1993, June 1993, January 1996, June 1996 and July 1996. The lava flows generally reached the sea, thus adding to the island's landmass. Calculation of the material that was ejected during that time in the form of lava and loose material was 22 million m3 and the addition of land was 380,000 m2. The height of Mount Anak Krakatau reaches 305 m asl.
2001	Strombolian ash eruption on 5 July.
2005 2007   2008 2010 2011	On 24 - 26 September 2005, there was an increase in the number of earthquakes. On 20 - 22 October 2007 the seismic activity increased again. On 23 October 2007 there was an eruption of ash as high as 200m. The results of visual observations on October 25, 2007 (Patria et al, 2007), there is a new eruption hole on the southern wall of Mount Anak Krakatau. On April 1 - 20 there was an increase in activity. The results of direct observation of Mount Anak Krakatau on April 15-16, 2008 showed that there was an eruption of ash accompanied by the ejection of incandescent material, taking place every 5 - 15 minutes with an altitude ranging from 100 - 500 meters. Starting October 10, 2010, there was an eruption of ash accompanied by ejection of incandescent material with a height of smoke ranging from 100 to 1700 m and has been taking place every day until now.

Tsunami caused by the 1883 eruption of Krakatau

Tsunamis can occur due to tectonic earthquakes, underwater volcanic eruptions, landslides on the seabed, pyroclastic flows/lava into the sea. Of the 106 tsunami events, most of them came from volcanic activity, mainly due to underwater volcanic eruptions, or tectonic earthquakes accompanied by volcanic eruptions.

The 1883 Krakatau eruption caused the loss of two volcanoes (Danan and Action) and part of Mount Rakata. This eruption caused a tsunami that swept away small towns along the coast of Banten and South Lampung, including the town of Teluk Betung. In Teluk Betung, the tidal wave reaches a height of 20 m. A ship, "The Berouw" which was in Teluk Betung Harbor at that time, was thrown 3,300 m into the forest. Furneaux, 1964 obtained information that the Krakatau boom was heard in Teluk Betung shortly after 10:00 and the tidal wave reached Teluk Betung town at 11.03, causing heavy damage to Teluk Betung town and killing lk. 5000 inhabitants, including 3 European nationals and 2,260 local residents.

The city of Merak, located on the Banten peninsula, was hit by tidal waves as high as 30 m and 40 m. This tidal wave also swept across Semangko Bay shortly after ravaging Betung Bay and the waves were not as high as those towards Lampung Bay, but were quite destructive along the coastline and damaged many villages and casualties, including 2,500 people died in the village of Benewani, 327 were missing in Tanjungan and Tanot Baringin and 244 people in Beteong. Tidal waves as high as 13.6 m also hit the concrete Bengkulen lighthouse and killed 10 people who were working.

In the Banten area, the entire coast was hit by tidal waves, many villages were hit by waves and killed residents including a priest on Prince Island. In Tangerang, a tidal wave as high as a person swept through the village, and within minutes the wave returned washing away people, animals, houses and trees. In this incident, it was recorded that 1,974 local residents and 46 Asian nationalities of the Karanghantu population were killed.

The tidal wave that left Krakatau at 10.00 am propagated in 2 hours 30 minutes to reach Jakarta, which is 169 km away. Sea water rose rapidly from 11.30am and 12.15pm a large tidal wave swept the coast of Jakarta, exceeding the maximum wave height gauge. The water receded again at 2:48 pm so that the wave height gauge could be read again. At Tanjung Priuk, the sea wave height at that time was an average of 3 m in a few minutes. In this incident, it was recorded that 300 fishermen were killed and one Chinese village was destroyed.

The tsunami waves caused by the eruption of Krakatau also moved westward towards the Indian Ocean, reaching the Good Hope peninsula, then north towards the Atlantic Ocean. This tsunami symptom was found in Cape Town (13,032 km) and almost all the coasts around the Indian Ocean and Atlantic Ocean. Wave height gauges at Cape Horn Harbor (14,076 km) and Panama (20,646 km) showed tidal waves with an average speed of 720 km per hour, and it was even reported that this tsunami reached the English Channel, which is 19,873 km from Krakatau.

 

Source : https://vsi.esdm.go.id