Wednesday, June 2, 2010

MOST DESTRUCTIVE ERUPTION OF INDONESIA VOLCANOES

Catalismic volcanic aoutbursts of Plinian Type as a result self intensification phase of gas explosion could be occurred at the end of Perret Phase (According to volcanologist, Perret study eruption of volcano Vesuvius in 1906).This Perret Phase often come together / or endded by destruction of partly structure of the volcano.


ANCIENT

In Indonesia, there were at least three wellknown powerful destructive volcanic eruptions in ancient era that highly possible influenced Indonesians ancient culture in past, there were: TOBA, SUNDA, and MERAPI, but more ancient ones are TOBA and SUNDA. Eruption of TOBA in north Sumatra, approx 74000 years, caused destruction of Paleotic Culture of ancient Indonesian. SUNDA: Eruption complex of volcano SUNDA in west Java, more less 20 centuries ago, caused  destruction of young Neolitic Culture of Sunda.

MORE HISTORIC

Current welknown desctructive Plinian Type, specifically Ultra - Plinian in history of Indonesia volcano eruptions are : Krakatau and Tambora.According to the Smithsonian Institution's Volcanic Explosivity Index , a VEI of 6 to 8 is classified as "Ultra Plinian."They are defined by ash plumes over 25 km (16 mi) high and a volume of erupted material 10 km3 (2 cu mi) to 1,000 km3 (200 cu mi) in size. Eruptions in the "Ultra Plinian" category include Lake Toba ( approx 74000 years ago ), Tambora (1815), and Krakatoa (1883).

Eruption Krakatau Volcano 1883 on the Sunda Strait triggered Tsunami.Krakatau magma chamber depth was very deep approx 50 km, and the gas pressure was extremely high, so that the eruption was able to generated today very large marine volcanic Caldera. However,historic eruption of Tambora was 4 times more powerful Ultra Plininian Eruption than Krakatau.

In case of Tambora, the cataclysmic eruption occurred on 11 April 1815 was initiated by Plinian eruption type on 5 April.The type plinian eruptions occurred twice and ejected gray pumice and ash to form stratified deposits as thick as 40-150 cm on the slopes.Following this, on 11 April the first pyroclastic surge was generated and progressively became greater extending to almost whole direction. Pyroclastic surge and flow deposits buried ancient villages.

Impact of volcanic eruption by Tambora volcano to global earth condition : Huge quantities of erupted ash and volcanic aerosols inferred with incoming solar radiation to the earth,causing global climate changes for one to two years, and caused large parts of the Earth in year without a summer.(Updated: 2016)


REFERENCE:

1.JURNAL GEOLOGI INDONESIA, Vol. 1 No. 1 March 2006.
2.liquisearch.com/plinian_eruption/ultra_plinian
3.MAJALAH GEOLOGI INDONESIA, Vol. 26 No. 2 August 2011.

4.Data Dasar Gunung Api Indonesia. 1979.


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