Ijen Crater
A volcano in East Java: blue flames of burning sulfur at night, then a turquoise acid lake and miners hauling heavy baskets at dawn.
What it is
Kawah Ijen is a crater in East Java holding a turquoise lake about a kilometer wide. It is one of the most acidic lakes on Earth, with a pH close to zero. At night, sulfuric gases escaping from cracks near the shore ignite into the famous blue fire. Sulfur is still mined here by hand: miners carry baskets weighing 75–90 kg out of the crater.
When and how
The trail starts at Paltuding: about 3 km and 1.5–2 hours to the rim. Hikers set off at 1–2 a.m. to catch the flames before dawn. Descending into the crater is not always allowed, and only with a local guide, depending on gas levels. A basic medical certificate is required; the medical post at the trailhead issues one. The park closes on the first Friday of each month for maintenance. The dry season, May to September, is best.
Tip
Bring or rent a proper gas mask: the wind can push the plume onto the trail at any moment.
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