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The Devastating 1983 Eruption of Colo Volcano, Una-Una Island, Central Sulawesi, Indonesia

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In April 1960 a series of strong tectonic earthquakes took place in the vicinity of the Colo volcano on the island of Una-Una situated in the Gulf of Gorontalo, Central Sulawesi. Unlike that of 1898 these earthquakes were not followed by an eruption of the Colo volcano but only caused a slight incresase in temperature of the solfatara fields. Strong earthquakes were again felt in August 1982, generating fissures and cracks in the island, however without any sign of increase in the activity of the volcano. Again on July 14, 1983, a great number of tectonic earthquakes jolted the island and reached a maximum of 4.6 on the Richter Scale on the July 19 causing the occurrence of big landslides near the summit of the volcano. The epicenter belongs to the same cluster of shallow earthquakes as that of 1960. Movements indicate normal faulting with a strike-slip component. Already on July 18, 1983, the first phreatic eruption of the Colo volcano occurred reaching a height of about 500 m. On July 23 at 09:35, 4 days after the occurrence of the biggest earthquake, the authors flew above the island and were welcomed by the first magmatic eruption with ash reaching a height of about 1500 m. Paroxysm preceded by a series of earthquakes of intermediate depth occurred at 16:00 hours the same day, or seven hours after the reconnaissance flight. The whole island was blasted and destroyed by nuée ardente, covering 90% of the 8 x 9 km circular island. Thickness of the deposits in the hills was 2 meters and in the valleys about 6 meters. Ash carried by the wind in a southwest direction reached Pulau Laut, SE Kalimantan covering a distance of about 900 km. This is the biggest known eruption of the Colo volcano in history. All the inhabitants (7000 people) were evacuated in time and the local government succeeded in evacuating the last hundred people from the island only one day before the paroxysm. All houses and coconut trees were destroyed and all livestock, wild life etc. perished. The nuée ardente swept the coastal area and the sea around the island, killing fish and other marine life.
The eruption of the Colo volcano is an excellent example of an eruption preceded by very distinct precursors. The preliminary conclusion drawn is that a "dying volcano" can be reactivated and could become very dangerous if triggered off by big earthquakes with epicenters situated nearby and characterized by tensional movements. The Colo volcano on Una-Una Island could be related to a subduction zone in the Sulawesi Sea dipping to the southeast and not to the one dipping to the northwest which is associated with the Minahasa volcanic belt.

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Ketersediaan

Informasi Detail

Judul Seri

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No. Panggil

PVG S.83-2

Penerbit

Hannover : DEPARTEMENT OF MINES AND ENERGY., 1983

Deskripsi Fisik

21hlm; gbr

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

eruptions

Info Detail Spesifik

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Pernyataan Tanggungjawab

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Informasi Lainnya

Kode Wilayah

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Pulau Dan Lembar Peta

Sulawesi

Provinsi

Sulawesi Tenggara

Koordinat - Latitude

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Koordinat - Longitude

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Versi lain/terkait

Lampiran Berkas