At the far eastern tip of Java's landscape rises one of the planet's most impressive volcanic craters: Kawah Ijen. This natural wonder is home to the world's largest acid lake, yet it also breathes out breathtaking blue flames. It goes without saying that this is a one-of-a-kind attraction that serious trekkers must experience during their travels through Indonésie.

History

Kawah Ijen is part of Mount Ijen, which formed 50,000 years ago following a volcanic eruption of the Old Ijen volcano, whose origins date back approximately 250,000 years. This eruption caused near-total destruction of the volcano, giving rise to the current Kendeng caldera. Subsequently, cones began to form along its southern rim. One of these cones is Kawah Ijen. Its age is estimated at 2,590 years.

The first eruption of Kawah Ijen observed by Westerners occurred in 1796. From that year until 2002, ten eruptions had taken place at the site. With the exception of those in 1875, none of them caused significant material damage or loss of life.

In 1921, Kawah Ijen welcomed a dam built by Dutch colonists. This structure, still present at the site at a breach in the crater, was constructed to regulate the lake's water level and prevent overflow during the wet season, which could otherwise destroy villages and coffee plantations nestled below in the Kendeng caldera.

What to Do at Kawah Ijen?

Marvel at the Acid Lake

Seeing Kawah Ijen's lake is the primary reason tourists make the journey. Its magnificent turquoise color will surely astound you—a hue born from the extreme acidity of its waters. These are indeed the most acidic on the planet, with a pH hovering around 0.2.

Spanning 45 hectares, Kawah Ijen's lake stretches 1 km in length and 600 meters in width. It is oval in shape. Its waters exit through a breach in the crater and subsequently form acidic rivers that journey some forty kilometers before emptying into the Java Sea.

Witness the Legendary Blue Flames (Night Visit)

Observing the blue flames is an experience forever etched into memory. The best time to see them is at night. Night treks are admittedly more challenging than daytime counterparts, yet they are worthwhile for the singular beauty of these flames.

The blue flames are not lava, but rather the result of combustion from sulfurous gases escaping the crater's fumaroles. When these gases, rich in sulfur dioxide and hydrogen sulfide, come into contact with air, they ignite due to the crater's elevated heat, creating spectacular blue glows.

Meet the Sulfur Porters

Beyond the site's incredible landscape, "the sulfur porters" also contribute to Kawah Ijen's renown. These men, hailing from villages surrounding the Ijen plateau, make constant trips carrying sulfur blocks in heavy shoulder yokes. These miners are paid according to the weight they bring back. However, rules are strict—baskets must weigh no less than 60 kg.

The work of sulfur porter carries numerous dangers. Beyond physical exertion—particularly high-altitude walking and ore transport—prolonged exposure to chemicals takes a toll on their health. Vapors from the acid lake and solfataras contain substances such as hydrochloric acid, sulfuric acid, and sulfur dioxide, which can damage mucous membranes, eyes, and skin. The life expectancy of these sulfur porters is estimated at 40 to 50 years.

FAQ

When Should You Visit Mount Ijen?

The best time to visit Kawah Ijen is during the dry season, from April through early November. Avoid the rainy season, between late December and March, as precipitation can last throughout the day.

- From Banyuwangi

Banyuwangi is the closest city on Java's island to Kawah Ijen. You can reach it by train or bus from Malang, Surabaya, Probolinggo, or Yogyakarta. The city also has an airport.

The trailhead for the hike to the crater is Paltuding, approximately two hours' drive from Banyuwangi. The ascent typically takes between 1.5 and 2 hours.

- From Bali

The city of Banyuwangi is accessible by plane from Denpasar, Bali's capital. You can also reach it by ferry from Gilimanuk port at the far western tip of the island. The boat docks at Ketapang port on Java, and the crossing takes less than an hour. Then take a taxi to Banyuwangi. This second leg of the journey takes only 20 minutes.

Is a Guide Necessary for the Hike to Kawah Ijen?

While not mandatory, hiring a guide is strongly recommended, especially if you plan to trek at night. A guide ensures safety, knowledge of the trail and crater, and will assist you during the descent.

What Is the Difficulty Level of Ascending Ijen Volcano?

The climb to Kawah Ijen can be considered difficult for casual trekkers. The trail features fairly steep slopes with a 500-meter elevation gain over 3 km. Additionally, sulfurous gas emissions can be irritating.

What Should You Bring?

Pack gas masks, scarves, and warm clothing to protect yourself from the volcanic gas emissions, smoke rising from the lake, and winds. A headlamp is essential if you intend to undertake a nighttime visit.