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Report on Merapi (Indonesia) — February 2002

Bulletin of the Global Volcanism Network, vol. 27, no. 2 (February 2002)
Managing Editor: Richard Wunderman.

Merapi (Indonesia) Heightened lava dome activity from August 2001 through at least February 2002

Please cite this report as:

Global Volcanism Program, 2002. Report on Merapi (Indonesia). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 27:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200202-263250.

Volcano Profile |  Complete Bulletin


Merapi

Indonesia

7.54°S, 110.446°E; summit elev. 2910 m

All times are local (unless otherwise noted)


During November 2001 through at least February 2002, seismic activity at Merapi was dominated by avalanche earthquakes. Generally white, thin, low-pressure plumes rose as high as 1.3 km above the summit. COSPEC-measured SO2 emission rates ranged from 66 to 225 ton/day (table 13).

Table 13. Seismicity, plume heights (in meters above the summit), and average SO2 fluxes at Merapi during 29 October 2001 through 24 February 2002. Courtesy VSI.

Date Avalanche signals Tectonic earthquakes Multiphase earthquakes Plume height (above summit) Average SO2 flux (tons/day)
29 Oct-04 Nov 2001 786 1 -- 480 78-121
05 Nov-11 Nov 2001 823 -- -- 520 --
12 Nov-18 Nov 2001 783 1 4 520 67-143
19 Nov-25 Nov 2001 737 1 3 625 66-98
26 Nov-02 Dec 2001 865 1 5 60 --
03 Dec-09 Dec 2001 -- -- -- 779 --
17 Dec-30 Dec 2001 1568 1 1 1100 66-118
30 Dec-06 Jan 2002 695 4 2 300 65-140
07 Jan-13 Jan 2002 851 1 7 500 --
14 Jan-20 Jan 2002 853 4 3 750 120-225
21 Jan-27 Jan 2002 979 5 7 1300 83-218
28 Jan-03 Feb 2002 855 3 8 650 92-187
04 Feb-10 Feb 2002 703 1 120 200 --
11 Feb-17 Feb 2002 600 4 31 100 --

Rainfall was heavy at times; during early and late November the maximum weekly rainfall rate was 44 mm/hour, and during 12-18 November the maximum rainfall rate was 78 mm/hour. Despite the heavy rainfall, no lahars were reported. Fumarole temperatures in the Gendol crater during November ranged from 430-570°C.

Incandescent lava avalanches traveled distances of 2.5 to 3 km and flowed toward the headwaters of the Sat and Bebeng rivers and, to a lesser extent, the headwaters of the Lamar and Senowo rivers. During 28 January-3 February 194 of these avalanches occurred.

A pyroclastic flow on 18 December traveled ~1 km toward the headwaters of the Bebeng river. Minor pyroclastic flows were reported throughout the remainder of the report period. During 4-10 February, 7 pyroclastic flows traveled 2.7 km to the Sat river and 2.5 km to the Bebeng river. During 11-17 February, 7 low-frequency earthquakes were recorded and the following week 1 low-frequency event was recorded. Merapi remained at Alert Level 2 throughout the report period.

Geologic Background. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities during historical time.

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