A short reflection on Kawah Ijen, Java – Lucy Hart

The World’s Largest Acidic Volcanic Crater Lake

Kawah Ijen is an active composite volcano, located within the Pleistocene Ijen caldera, at the Easternmost part of Java island, Indonesia; the volcano complex is a group of small stratovolcanoes, constructed within the 20-km-wide caldera.

This summer I was lucky enough to see Kawah Ijen for myself.

Kitted with gas masks and walking boots, we ascended  to 2386 m above sea-level, starting at the Paltuding Area. After a positively vertical two-hour climb up to the crater’s rim, we descended for 45-minutes to reach the crater bank.

Awed by the famous ‘blue fire’ – formed by the combustion of sulphuric gases and a subsequent reaction with Oxygen in the air – we were simultaneously met with occasional plumes of sulphur gas (marginally unpleasant).

Blue Fire at the Ijen crater

Before Sunrise, we climbed back up to the crater rim. Over the next hour the turquoise lake was unveiled (despite the inviting colour, the pH of the lake is 0.5..so we put away our swimming costumes). The pH owes to the hydrogen chloride gas emitted by the volcano, reacting with the water to form condensed hydrochloric acid. Best to look but not touch.

Sun Rising over the crater bank


Sulfur clouds at Ijen
Sulphur gas clouds at Ijen

Such noxious sulphur fumes expose humans to respiratory diseases; short-term exposure is linked to airway constriction and asthma symptoms. Health experts recommend that regular workplace exposure does not exceed two parts per million; USGS scientists have found levels more than 30 times that near to the site where these men work, posing a serious and permanent health risk. Despite this, miners journey twice a day, carrying up to 100 kilos of sulphur. 

Mining company PT Candi Ngrimbi installed ceramic pipes on an active vent near the lake, in order to speed up sulphur formation. The sulphur gases are piped down the sloping mound, cooling, condensing and solidifying into hard sulphur. Miners break off this sulphur and are paid for what they carry back; 13 tons of raw sulphur are obtained every day from the volcano. 

If you ever find yourself in Java, it is certainly worth the climb.

All images by Lucy Hart ©


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