Report on Marapi (Indonesia) — January 2005

Bulletin of the Global Volcanism Network, vol. 30, no. 1 (January 2005)
Managing Editor: Richard Wunderman.

Marapi (Indonesia) Small eruptions and seismicity during August to October 2004

Please cite this report as:

Global Volcanism Program, 2005. Report on Marapi (Indonesia). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 30:1. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.BGVN200501-261140.

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Marapi

Indonesia

0.381°S, 100.473°E; summit elev. 2891 m

All times are local (unless otherwise noted)


The most recent previous explosive activity at Marapi peaked during 13-18 April 2001, when a total of 150 explosions occurred that sent ash plumes to 2 km above the summit (BGVN 27:01). This report covers the interval 5 August to 10 October 2004. On 5 August 2004 Marapi generated a small eruption with a gray to black ash cloud that rose to 500-1,000 m above the summit. Its hazard status was raised to Alert Level II (yellow), where it remained throughout this period.

Total numbers of seismic events from 2 August through 10 October 2004 are listed in table 5. During some weeks in August the number of earthquakes increased markedly. A thin white plume rose to 50 m above the summit on 10 August. During 16-29 August a thin white-gray plume rose to ~ 75-100 m. Similar plumes rose to ~ 50 m during 27 September-3 October and to ~ 300 m during 4-10 October. Seismic signals inferred to be related to emissions were elevated during several weeks of the reporting interval, particularly in August (table 5).

Table 5. A summary of volcanic seismicity at Marapi during 2 August to 10 October 2004. Courtesy of DVGHM.

[Skip text table]
    Date             Volc A    Volc B    Tremor    Emission

    02 Aug-08 Aug       1        11        --         --
    09 Aug-15 Aug       2         6        --         20
    16 Aug-22 Aug      --         3        --         21
    23 Aug-29 Aug      --         3         2         14

    20 Sep-26 Sep      --        --        --         --
    27 Sep-03 Oct       1        --        --         --
    04 Oct-10 Oct       3        --        --          8

There were no MODIS-MODVOLC alerts at Marapi during 2004.

Geologic Background. Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra's most active volcano. This massive complex stratovolcano rises 2000 m above the Bukittinggi plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.

Information Contacts: Directorate of Volcanology and Geological Hazard Mitigation (DVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (Email: dali@vsi.esdm.go.id, URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Center (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/advisories.shtml, Email: Darwin.vaac@bom.gov.au).