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.
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).
|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/).