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Kawah Ijen

Short answer: Kawah Ijen is the crater of the Ijen volcano in East Java, Indonesia. It holds a turquoise lake rich in sulfuric and hydrochloric acid.

Its famous 'blue fire' (locally api biru) isn't lava. Photographer Olivier Grunewald, who documented it for years, told National Geographic and Smithsonian that the glow comes from burning sulfur-rich gases. These leave cracks at high pressure and temperatures up to 600 °C and ignite in air above about 360 °C, with flames up to about 5 m high. Some of the gas condenses into liquid sulfur that keeps burning as it runs downhill, which looks like flowing blue lava. The flames are faint, so they show only at night. USGS geologist John Pallister told National Geographic that miners sometimes light the sulfur themselves, which adds to the flames in night photos. Ijen is also a working sulfur mine. Ceramic pipes channel gas from a vent by the lake, and it condenses into molten sulfur that hardens yellow. Miners break off chunks and carry them out in baskets. Wikipedia, citing several reports, puts typical loads at 75 to 90 kg, carried up about 300 m to the crater rim and then about 3 km down, often twice a day. A 2024 study measured sulfur dioxide along the miners' path at 3.14 to 18.24 mg/m³, above the US EPA's 1.97 mg/m³ guideline. Miners reported eye irritation, coughing, headaches and shortness of breath. The footage shows bright blue flames and burning streams against the dark night slopes.

VideoWrite-up4 sources

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What should you know about Kawah Ijen?

Quick facts. Each one stands alone and has a stable ID you can cite.

  1. Kawah Ijen's blue glow is burning sulfur, not lava.

    DD-600-F01 · Write-up · Exhibit A (Not lava)

  2. Ijen's sulfur miners carry loads of about 75 to 90 kg.

    DD-600-F02 · Write-up · Exhibit D (A working mine)

Video transcript: Kawah Ijen: Blue Fire, Not Blue Lava

DID YOU KNOW? Kawah Ijen volcano in East Java, Indonesia, is renowned for its striking blue lava, a rare geological phenomenon. This electric blue glow, visible only at night, is not true lava, but results from the combustion of sulphuric gases. These gases, released at high pressures and temperatures up to 600 °C, ignite upon contact with oxygen-rich air, producing vibrant blue flames. As the sulfur burns, some condenses into molten form, flowing down the volcano and creating the illusion of blue lava. NOW YOU KNOW!

Burned-in captions, read frame by frame (see transcript.md) · 27.5s Reel ·

Video coming soonKawah Ijen · Instagram Reel
Kawah Ijen: Blue Fire, Not Blue Lava Instagram Reel · · 27.5s

The write-up

Blue fire, not blue lava. Burning sulfur gas glows blue at night in East Java.

  1. Exhibit A

    Not lava

    The blue glow is burning sulfur-rich gas, not blue lava.

  2. Exhibit B

    Hot gas meets air

    Gas emerges at up to 600 °C and ignites in air, with flames up to about 5 m high.

  3. Exhibit C

    Burning rivers

    Some gas condenses into liquid sulfur that keeps burning as it flows downhill.

  4. Exhibit D

    A working mine

    Miners carry loads of about 75 to 90 kg up to the crater rim, often twice a day.

  5. Exhibit E

    Toxic air

    A 2024 study measured sulfur dioxide on the miners' path above the US EPA guideline.

Questions people ask about Kawah Ijen

What makes Kawah Ijen's blue glow?

Sulfur-rich gas burns blue.

Source: Write-up · Exhibit A (Not lava) · National Geographic: Stunning electric-blue flames erupt from volcanoes; Smithsonian Magazine: Why does this Indonesian volcano burn bright blue?

Up to what temperature does the gas emerge?

It ignites on contact with air.

Source: Write-up · Exhibit B (Hot gas meets air) · National Geographic: Stunning electric-blue flames erupt from volcanoes; Wikipedia: Ijen

How high can the flames reach?

Per Grunewald, via National Geographic.

Source: Write-up · Exhibit B (Hot gas meets air) · National Geographic: Stunning electric-blue flames erupt from volcanoes; Wikipedia: Ijen

On which island is Kawah Ijen?

East Java, Indonesia.

Source: Write-up · Exhibit A (Not lava) · National Geographic: Stunning electric-blue flames erupt from volcanoes; Smithsonian Magazine: Why does this Indonesian volcano burn bright blue?

How heavy are typical miners' loads?

Carried up to the crater rim and down the mountain.

Source: Write-up · Exhibit E (Toxic air) · Environmental health risk assessment and acute effects of SO2 exposure on traditional sulfur miners at Ijen Crater (2024, PMC)

Test Your Knowledge

All quizzes →

5 questions, all from this case file. Answers are revealed instantly.

  1. What makes Kawah Ijen's blue glow?

    1. Burning sulfur
    2. Blue lava
    3. Bioluminescent algae
    4. Copper minerals
    Show the answer

    Answer: A. Burning sulfur Sulfur-rich gas burns blue. Source: Write-up · Exhibit A (Not lava) · National Geographic: Stunning electric-blue flames erupt from volcanoes; Smithsonian Magazine: Why does this Indonesian volcano burn bright blue?

  2. Up to what temperature does the gas emerge?

    1. About 600 °C
    2. About 60 °C
    3. About 6,000 °C
    4. About 6 °C
    Show the answer

    Answer: A. About 600 °C It ignites on contact with air. Source: Write-up · Exhibit B (Hot gas meets air) · National Geographic: Stunning electric-blue flames erupt from volcanoes; Wikipedia: Ijen

  3. How high can the flames reach?

    1. About 5 m
    2. About 5 cm
    3. About 500 m
    4. About 5 km
    Show the answer

    Answer: A. About 5 m Per Grunewald, via National Geographic. Source: Write-up · Exhibit B (Hot gas meets air) · National Geographic: Stunning electric-blue flames erupt from volcanoes; Wikipedia: Ijen

  4. On which island is Kawah Ijen?

    1. Java
    2. Bali
    3. Sumatra
    4. Borneo
    Show the answer

    Answer: A. Java East Java, Indonesia. Source: Write-up · Exhibit A (Not lava) · National Geographic: Stunning electric-blue flames erupt from volcanoes; Smithsonian Magazine: Why does this Indonesian volcano burn bright blue?

  5. How heavy are typical miners' loads?

    1. About 75 to 90 kg
    2. About 5 kg
    3. About 500 kg
    4. About 1 kg
    Show the answer

    Answer: A. About 75 to 90 kg Carried up to the crater rim and down the mountain. Source: Write-up · Exhibit E (Toxic air) · Environmental health risk assessment and acute effects of SO2 exposure on traditional sulfur miners at Ijen Crater (2024, PMC)

Cite this case file

Easterling, Marcus. "Kawah Ijen." The Detail Department (DetailEnjoyer), case file DD-600, last updated Jun 19, 2025. https://detailenjoyer.com/case/kawah-ijen/

Permalink: https://detailenjoyer.com/case/kawah-ijen/ · Last updated

Markdown version

Cite a single fact by its ID, for example DD-600-F01 → https://detailenjoyer.com/case/kawah-ijen/#DD-600-F01

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