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Report on Karangetang (Indonesia) — May 2002

Bulletin of the Global Volcanism Network, vol. 27, no. 5 (May 2002)
Managing Editor: Richard Wunderman.

Karangetang (Indonesia) Small explosions and increased seismicity during April 2002

Please cite this report as:

Global Volcanism Program, 2002. Report on Karangetang (Indonesia). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 27:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200205-267020.

Volcano Profile |  Complete Bulletin


Karangetang

Indonesia

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

All times are local (unless otherwise noted)


During 25 February through at least 16 June 2002, seismicity at Karangetang was dominated by shallow volcanic (B-type) and tectonic earthquakes (table 4). Thick, white, medium-pressure plumes were typically emitted from the main crater (S) and reached 50-500 m above the crater rim. During late May through at least 16 June, a thin-medium white plume was emitted from crater II (N) and reached 150-200 m above the crater rim. During most of the report period a red reflection was observed around the summit at night, rising 10-75 m.

Table 4. Earthquakes recorded at Karangetang during 25 February through 16 June 2002. The Alert Level remained at 2 throughout this period. Courtesy VSI.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Multiphase Tectonic
25 Feb-02 Mar 2002 52 5 6 62
03 Mar-10 Mar 2002 44 20 2 201
11 Mar-17 Mar 2002 29 8 9 100
18 Mar-24 Mar 2002 15 8 6 83
25 Mar-31 Mar 2002 20 9 2 112
01 Apr-07 Apr 2002 27 3 2 71
08 Apr-14 Apr 2002 17 64 -- 82
15 Apr-21 Apr 2002 26 74 -- 147
22 Apr-28 Apr 2002 17 61 2 146
29 Apr-05 May 2002 28 99 6 139
06 May-12 May 2002 22 70 0 132
13 May-19 May 2002 8 77 1 112
20 May-26 May 2002 22 93 6 146
27 May-02 Jun 2002 18 1228 4 113
03 Jun-09 Jun 2002 13 119 3 75
10 Jun-16 Jun 2002 12 62 1 45

Several eruptions occurred during the report period. An eruption on 5 March at 1344 emitted ash that reached 1.5 km above the summit. Ash fell on the NE flank and a lava avalanche also occurred. During the week of 3-10 March, 1 earthquake was felt. On 23 March 2002 at 1115 a thundering sound was heard from main crater, followed by a lava avalanche that flowed down to Kahetang and Batu Awang rivers. A thundering sound was heard beginning at 1615 on 28 March until 2007 on 29 March. No lava avalanches occurred during this time, but 3 earthquakes were felt during the last week of March. A medium explosion on 7 April at 2115 emitted thick gray ash to ~400 m above the crater rim.

The number of deep and shallow volcanic earthquakes increased during April (table 4). An ash explosion on 12 May at 1116 emitted ash that reached 750 m above the crater before falling to the sea on the E side. The explosion was followed by a lava avalanche that flowed ~500 m down the Batu Awang and Kahetang rivers. An explosion on 26 May at 1747 emitted white-gray ash that reached 300 m above the crater rim before falling to the sea on the W side. During 3-9 and 10-16 June, 2 and 5 small explosions occurred per week, respectively. Karangetang remained at Alert Level 2 throughout the report period.

Geologic Background. 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 island. 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 in the historical record (Catalog of Active Volcanoes of the World: 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/).