Report on Sangeang Api (Indonesia) — December 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 12 (December 1985)
Managing Editor: Lindsay McClelland.
Sangeang Api (Indonesia) Summit explosions in July and December
Please cite this report as:
Global Volcanism Program, 1985. Report on Sangeang Api (Indonesia) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 10:12. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198512-264050
Sangeang Api
Indonesia
8.2°S, 119.07°E; summit elev. 1912 m
All times are local (unless otherwise noted)
"Sangeang Api continued to erupt in December. Compositions of 30 July pumice and mid-August dense lava bombs are given in table 2."
Table 2. Whole rock analyses of samples collected from Sangeang Api. X-ray fluorescence analyses by the USGS Laboratory, Denver, Colorado. Sample 1: pumice from eruption on 30 July 1985. Sample 2: ejected block, dense lava explosion mid-August 1985. Total iron expressed as Fe2O3; loss on ignition at 900°C.
| Element | Sample 1 (pumice) | Sample 2 (block) |
| SiO2 | 53.8 | 49.3 |
| Al2O3 | 18.9 | 17.9 |
| Fe2O3 | 7.23 | 11.1 |
| MgO | 2.51 | 4.60 |
| CaO | 7.30 | 10.2 |
| Na20 | 4.33 | 3.07 |
| K20 | 3.60 | 2.40 |
| TiO2 | [0.66] | 1.03 |
| P2O5 | 0.38 | 0.32 |
| MnO | 0.22 | 0.23 |
| LOI | 1.09 | 0.05 |
| Total | [100.02] | 100.2 |
Geological Summary. Sangeang Api volcano, one of the most active in the Lesser Sunda Islands, forms a small 13-km-wide island off the NE coast of Sumbawa Island. Two large trachybasaltic-to-tranchyandesitic volcanic cones, Doro Api and Doro Mantoi, were constructed in the center and on the eastern rim, respectively, of an older, largely obscured caldera. Flank vents occur on the south side of Doro Mantoi and near the northern coast. Intermittent eruptions have been recorded since 1512, most of them during in the 20th century.
Information Contacts: Suparto S. and T. Casadevall, VSI.
