Report on Karangetang (Indonesia) — May 2003

Bulletin of the Global Volcanism Network, vol. 28, no. 5 (May 2003)
Managing Editor: Edward Venzke.

Karangetang (Indonesia) Ash explosions from January through May 2003

Please cite this report as:

Global Volcanism Program, 2003. Report on Karangetang (Indonesia). In: Venzke, E (ed.), Bulletin of the Global Volcanism Network, 28:5. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.BGVN200305-267020.

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Karangetang

Indonesia

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

All times are local (unless otherwise noted)


During 6 January-4 May 2003 explosions produced ash that fell on various parts of the crater. The S (main) crater emitted "white-gray ash" that reached 150-400 m high. On some nights, a red glow was visible reaching 25-50 m over the crater. The N crater emitted a "white-thin ash" plume that reached 50-300 m high. Fluctuating seismicity was dominated by multiphase earthquakes and emissions (table 7). The Alert Level remained at level 3 (on a scale of 1 to 4) through at least 4 May.

Table 7. Seismicity at Karangetang during 6 January-4 May 2003. Courtesy VSI.

[Skip text table]
    Date (2003)       Deep     Shallow    Explosions
                    volcanic   volcanic
                    (A-type)   (B-type)

    06 Jan-12 Jan      11         16          2
    13 Jan-19 Jan       9         16          2
    20 Jan-26 Jan      12         37         --
    27 Jan-02 Feb       6         28          1
    03 Feb-09 Feb      17         84          1
    10 Feb-16 Feb       9         30          1
    17 Feb-23 Feb       9         46         --
    24 Feb-02 Mar      48         68         --
    03 Mar-09 Mar      19         29          1
    10 Mar-16 Mar      14         11         --
    17 Mar-23 Mar      24        145         --
    24 Mar-30 Mar      21         68         --
    31 Mar-06 Apr       8         83         --
    07 Apr-13 Apr      18        143         --
    14 Apr-20 Apr      12        257         32
    21 Apr-27 Apr      13        373          2
    28 Apr-04 May      32        255         --

    Date (2003)      Multiphase   Emissions   Tectonic   Avalanches

    06 Jan-12 Jan       178          178         28          --
    13 Jan-19 Jan       133           42         40          --
    20 Jan-26 Jan       189           52         27          --
    27 Jan-02 Feb       228          118         22          --
    03 Feb-09 Feb       162          306         23          --
    10 Feb-16 Feb        85          102         16          --
    17 Feb-23 Feb        97            8         32          --
    24 Feb-02 Mar        78           17         34          --
    03 Mar-09 Mar        48            9         24         398
    10 Mar-16 Mar        27            7         30         125
    17 Mar-23 Mar        82            4         23           4
    24 Mar-30 Mar        35            1         33           2
    31 Mar-06 Apr        30           --         36          --
    07 Apr-13 Apr       116            6         50          --
    14 Apr-20 Apr       226           26         32           7
    21 Apr-27 Apr        93            6         17         309
    28 Apr-04 May       243            1         21          29


On 11 and 12 January, ash explosions at the S crater were accompanied by glowing material that reached 200 m high and scattered 500 m toward the E and W parts of the crater. An ash column rose up to 500 m above the crater. Two explosions at the S crater on 14 January produced an ash column up to 300 m high; glowing material rose up to 50 m and fell around the crater. Some of the material entered the Beha River, and ash fell into the sea E of the island. Explosions on 29 January and 6 February caused ashfall SW (Beong village) and SSW (Akesembeka village, Tarurane, Tatahadeng, Bebali, and Salili), respectively. A booming noise was heard frequently throughout the report period, and during early February was sometimes accompanied by thick gray emissions up to 350 m above the crater.

Beginning in early March, the booming noise was accompanied by glowing lava avalanches that traveled from the summit towards the Kahetang (1,250 m), Batuawang (750 m), Batang (1,000 m), and Beha (750 m) rivers. On 6 March an explosion from the S crater ejected ash 750 m high that fell in the E part of the crater. The noises and avalanches decreased during mid-to-late March.

An explosion on 15 April was followed by lava avalanches toward the W and S parts of the crater. A loud blasting sound was heard, and a dark-gray ash column reached 1,500 m. Ash fell to the E around Dame and Karalung villages, and over the sea. Lava avalanches from the S crater traveled 1,000 m toward the Batang and Batu rivers. On 20 April another explosion produced a 1,500-m-high ash column, and ash fell E over the sea. This explosion was followed by lava avalanches and a pyroclastic flow toward the Batang river that reached as far as 2,500 m. Lava avalanches extended 1,500 m down the S and W slopes. Blasting noises occurred for about 3 minutes.

On 22 April an explosion ejected ash and glowing material. The ash column reached 1,750 m and ash fell on the W slope, including Lehi, Mini, Kinali, and Hiung villages, while glowing material rose up to 750 m. This explosion was followed by lava avalanches towards the W and S that were accompanied by a pyroclastic flow toward the Batang river that extended 2,250 m. On 24 April, an explosion ejected ash to 750 m and ash fell eastward into the sea. Glowing material from the explosion traveled toward the W slope. During late April, the booming noises were once again accompanied by continuous glowing avalanches. These decreased during the first days of May.

Geologic Background. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, north 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 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 has also produced pyroclastic flows.

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