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Report on Karangetang (Indonesia) — January 2002


Bulletin of the Global Volcanism Network, vol. 27, no. 1 (January 2002)
Managing Editor: Richard Wunderman.

Karangetang (Indonesia) Lahars cause damage in January; explosions and lava flows in February

Please cite this report as:

Global Volcanism Program, 2002. Report on Karangetang (Indonesia) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 27:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200201-267020



2.781°N, 125.407°E; summit elev. 1797 m

All times are local (unless otherwise noted)

During 5 November 2001 through 24 February 2002, seismicity continued at Karangetang, and plumes were observed rising above the summit (table 3). The lava flows that began during late April and early May 2001 (see BGVN 26:10) stopped around 25 October. Multiphase earthquakes, associated with lava dome growth, had not been registered since September but began again during early November.

Table 3. Seismicity and plumes observed at Karangetang during 5 November through 24 February. The Alert Level remained at 2 throughout this period. Courtesy VSI.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Tectonic Multiphase Observation (plume heights are above summit)
05 Nov-11 Nov 2001 7 -- 51 11 White medium-thick plume rose 100 m above N crater, 50 m above crater II; incandescence to 20 m
12 Nov-18 Nov 2001 14 4 49 -- White medium-thick plume rose 600 m; incandescence to 25-50 m
19 Nov-25 Nov 2001 12 9 36 -- --
26 Nov-02 Dec 2001 14 2 66 5 White medium-thick plume rose 300 m above main crater, 150 m above crater II
03 Dec-09 Dec 2001 13 9 45 11 White thin-medium plume rose 50-250 m above main crater, 100 m above crater II
17 Dec-30 Dec 2001 17 16 60 12 White medium-thick plume rose 500 m above main (S) crater, 50 m above crater II
30 Dec-06 Jan 2002 10 5 9 7 Lahars on 3 January
07 Jan-13 Jan 2002 18 8 56 9 White medium-thick plume rose 400 m above summit, incandescence inside the plume to 50 m
14 Jan-20 Jan 2002 4 7 44 1 --
21 Jan-27 Jan 2002 4 6 29 6 --
28 Jan-03 Feb 2002 8 1 36 12 White medium-thick plume rose 100 m above main (S) crater, 75 m above N crater; incandescence to 25 m
04 Feb-10 Feb 2002 407 215 967 23 Incandescence to 25 m
11 Feb-17 Feb 2002 281 73 102 3 Ash to WSW, lava flows, incandescence to 25 m
18 Feb-24 Feb 2002 113 16 100 1 Incandescence to 25 m

During the first days of 2002 heavy rains near the summit resulted in cold lahars along the Kahetang river on the E flank. On 3 January around 1200 a lahar traveled ~260 m and was ~10-125 cm thick near Terminal and Pelabuhan Ulu Siau. The volume of the lahar was estimated to reach 40,000 m3. In this area, a total of 52 houses were destroyed. Near Bebali village, a lahar traveled ~60 m and covered the road along Ulu Siau city to Ondong village to a thickness of ~75 cm. The volume of the lahar was estimated at 600 m3. In this area, 9 houses and a church were damaged.

Seismicity increased during early February, and a thundering sound was heard frequently coming from the main (S) crater, often accompanied by a sulfur smell. During a 3-day period in early February, 82 earthquakes occurred with magnitudes of 1-3. The earthquakes often caused sliding of the unstable 2001 lava. On 11 February, an explosion occurred that produced ash falls 0.5-1 mm thick to the WSW, reaching the Kanawong, Lehi, Mimi, Kinali, and Pehe villages. Incandescent lava flows traveled up to 1.5 km down the Beha river (W slope) and Kahetang river (E slope). Seismicity was still high but decreased after the 11 February explosion. Loud noises, sulfur smells, and incandescence were observed through at least 24 February.

Geological Summary. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented (Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts have produced pyroclastic flows.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).