Kawah Ijen Volcano

Kawah Ijen volcano is one of several volcanoes located in the 15km diameter Ijen Caldera in E Java, Indonesia. The caldera rim is still visible in places, but has been partially buried by Kawah Ijen, 2800m high Gunung Merapi (not to be confused with Merapi volcano near Yogyakarta), Gunung Rante and Gunung Pendil volcanoes. The caldera is today largely filled with coffee plantations. Kawah Ijen harbours a large warm acidic crater lake and an active sulphur mine. Due to its easy accessibility, turqoise lake and unique sulphur mining operation, the crater is regularly visited by tourists. The last recorded magmatic eruption of Kawah Ijen was in 1817. The eruption displaced the crater lake and resulted in inundation of several villages along the drainage route. Phreatic eruptions have been reported in 1796, 1917, 1936, 1950, 1952, 1993, 1994, 1999, 2000 (also minor ash emission), 2001, 2002 (with minor ash emission). The increasing frequency may reflect better reporting since the explosions are usually confined to the lake and cause little or no damage.

Crater of Kawah Ijen volcano containing highly acidic lake and solfatara (bottom left).	Sulphur Mining at Kawah Ijen Solfatara

Pipe used to extract molten sulphur from the solfatara	Small molten sulphur flow

The sulphur mining operation consists of a number of pipes driven into the solfatara. Solfatara temperatures nearing 250 'C have been reported, although chemical analysis of solfatara gases suggests temperatures inside to be above 300'C. Condensation of volcanic gases saturated with elemental sulphur (formed by SO2 + 2H2S = 3S + 2H2O reaction) occurs as they cool during passage through the pipes. Molten sulphur trickles out of the end of the pipes, solidifying nearby as it cools further. The miners then break up the sulphur deposits and carry them out of the crater and, via the weighing station, to a nearby sugar refinery. Due to unprotected exposure to volcanic gases and loads of up to 100kg per trip, the life expectancy of the miners is low (not much over 30 years).

The volcanic gases emitted are also responsible for the characteristics of the nearly 200m deep crater lake. Takano et al., 2004 (J. Volc. and Geotherm. Res. 135, p.299-329) extensively studied the crater lake. Injection rates of 340 tonnes/day of sulphur dioxide were calculated, accounting for the extreme acidity. Lake temperature and pH fluctuate and were reported at around 36'C and 0.1, respectively, near the surface in this study. Temperature and acidity change, along with visible lake surface changes such as colour fluctuations or local bubbling or upwelling can provide signs of increased activity along with seismic data which are regularly obtained. Also, observations by the mine workers can be taken into account, such as increased breathing difficulty or dizziness, suggesting changes in gas composition or levels. Interestingly, reports of birds falling into the lake (presumably due to intoxication by volcanic gases) have also been taken into account when assessing the risk of impending eruptions (Smithsonian Global Volcanism Program report 06/1997 (BGVN 22:06).

Miners working in intense gases with merely handkerkiefs for protection.	Miner carrying blocks of sulphur from the mine.	Small sulphur flow emanating from pipe in sulphur mine.

Further Photos

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