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Report on Merapi (Indonesia) — July 1992

Bulletin of the Global Volcanism Network, vol. 17, no. 7 (July 1992)
Managing Editor: Lindsay McClelland.

Merapi (Indonesia) Growing lava dome spawns avalanches; summit gas data

Please cite this report as:

Global Volcanism Program, 1992. Report on Merapi (Indonesia). In: McClelland, L. (ed.), Bulletin of the Global Volcanism Network, 17:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199207-263250.

Volcano Profile |  Complete Bulletin


Merapi

Indonesia

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

All times are local (unless otherwise noted)


The volume of the lava dome at the end of July was calculated at ~10.5 x 106 m3, of which 2.8 x 106 m3 were pyroclastic-flow and avalanche deposits. Glow from rockfalls tended to become less bright in late July, but the distance traveled by avalanches remained relatively constant, at up to 1,500 m (to the WNW). Gases at the Gendol solfatara field, in the S part of the summit crater, were sampled for analysis (table 6).

Table 6.Gas concentrations (in volume %) and temperatures (in °C) measured at Merapi's Gendol solfatara field, May-December 1992. Courtesy of S. Bronto.

Gas 06 May 27 Jun 09 Jul 23 Jul 08 Sep 22 Oct 03 Dec
H2 0.63 1.19 1.33 1.72 1.03 1.09 0.91
O2+Ar 0.015 0.05 0.09 3.05 0.04 0.02 0.005
N2 0.11 0.27 0.77 28.23 0.27 0.15 0.23
CO 0.03 0.04 0.06 0.09 0.05 0.05 0.06
CO2 4.57 8.48 11.17 29.09 4.46 3.21 4.48
SO2 0.79 1.57 1.77 10.86 0.71 2.20 0.95
H2S 0.44 1.35 1.10 1.66 0.32 0.40 1.08
HCl 0.11 0.29 0.42 6.37 0.17 0.40 0.51
H2O 93.31 86.76 83.29 18.95 92.96 92.18 91.76
Temp 802 818 820 813 816 807 824

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: S. Bronto, MVO.