The Blue Fire of Ijen
Inside an Indonesian volcano, rivers of electric-blue flame run down the rocks at night.
What was reported
At the Ijen volcano in East Java, visitors who hike up before dawn can see vivid blue flames flickering across the crater floor, sometimes seeming to flow down the slopes like liquid. The crater also holds the world's largest acidic lake, a bright turquoise.
Miners have long climbed into the crater to carry out heavy baskets of yellow sulphur by hand, working in the fumes.
Explanations offered
The blue light comes from sulphurous gases escaping through cracks at high temperature and burning as they meet the air; some sulphur condenses and burns as it flows, which looks like blue lava. The colour shows only at night. The gases are dangerous, and visitors wear masks.
- When
- Seen every night
- Where
- Ijen crater, East Java, Indonesia
- Witnesses
- Sulphur miners and visitors
- Status
- Explained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.