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), (?), 2011. The increasing frequency may reflect better reporting since the explosions are usually confined to the lake and cause little or no damage.
Various unverified sources claim that sudden gas release from the crater lake claimed the lives of numerous sulphur workers in 1976 (11-49) and 1989 (25). Such gas releases may occur with little warning in the future and probably represent the main hazard for visitors.

Crater of Kawah Ijen volcano containing highly acidic lake and solfatara (bottom left)	Miner breaking up sulfur for transport	Sulphur Mining at Kawah Ijen solfatara

Solfatara on flank of crater above acid lake	Natural sulfur pot damaged by miners	Untouched sulfur deposits

Many properties of sulfur (= sulphur) can be observed at the Kawah Ijen sulfur mine. The element tends to form polyatomic molecules such as the predominant cyclic form octasulfur. The cyclic structure changes its exact form at different temperatures. Melting temperature is about 115 'C with a boiling point of 444 'C. Significant vaporization, often incorrectly referred to as sublimation, occurs below the boiling temperature. Molten sulfur tends to get darker in colour as temperature increases, with orange flows often visible over the background of yellow solidified sulfur deposits. Sulfur can also self-ignite at temperatures as low as 248 'C and burns with a blue flame as sulfur dioxide gas is formed. These flames are a well-documented feature of Kawah Ijen and can be clearly seen at night. Several small fields of sulfur flares can be seen at the top of the active part of the solfatara. Burning flows of molten sulfur have been documented in the past, but workers presently rush to extinguish such flows as the resulting dark material is of no commercial interest for the miners.

Close-up of sulfur flare	Small burning sulfur flow during daylight	Sulfur flare zone

Burning sulfur oxidizes to reddish dioxide	Nighttime view of crater with blue flames at base of gas column

Areas of burning sulfur in mine	Areas of burning sulfur in mine

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

Sulfur frothing as if boiling, probably due to moisture under flow	Molten sulfur forms stalagtites	Pool of molten sulfur under stalagtities

Molten sulfur flows over smashed up older deposits	Molten sulfur flows over smashed up older deposits	Cooling sulfur gases form crystalline deposits in places

The volcanic gases emitted are also responsible for the characteristics of the nearly 200 meter 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.

	Kawah Ijen Acidic Crater Lake

Kawah Ijen Crater	Kawah Ijen Crater

Rafts of yellowish material floating on lake	Close-up of yellow "scum" floating on lake

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).

Images of Sulphur Mining Operation

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. From there they are transported to a processing facility in a nearby town. 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).

Solfatara with sulfur mine	Solfatara with sulfur mine

Solfatara with sulfur mine	Solfatara with sulfur mine viewed from crater rim

Pool for collecting spring waters for extinguishing or cooling sulfur	Worker waits for water to cool piping	Worker spraying water onto solfatara

Miners working in intense gases with merely handkerkiefs for protection.	Fresh sulfur deposit below pipe	Small sulphur flow emanating from pipe in sulphur mine.

Condensating sulfur dribbling from pipe	Condensating sulfur dribbling from pipe

	Worker breaking up sulfur accumulations at end of pipes

Collecting sulfur for transport	Classic means of transporting sulfur at Ijen	Lifting heavy baskets full of sulfur

Miner resting along climb from crater	Worker attaching sulfur load to weighing station

Weighing sulfur	Adjusting weights on scales	Receipt is provided from hut opposite scales

Important Visitor Information

Levels of gas at Kawah Ijen can reach dangerous levels, especially in the immediate vicinity of the solfatara. Depending on the wind direction, the trail into the crater may be shrouded in gas. Visitors should only visit the solfatara / mine with a gas mask having a suitable filter for removing a large proportion of the largely acidic gases. In the immediate vicinity of the sulfatara, even standard gas masks may not be able to cope with the high gas concentrations downwind (personal experience), potentially causing irreversible damage to the lungs. The acidic nature of the gases also leads to irritation and inflammation of the eyes.

Further, sudden releases of large volumes of gas from the lake may be fatal to those near the bottom of the crater.

Photovolcanica Full Index