Ijen Crater Lake
Interesting facts
- The lake drains through a breach in the crater wall at about 50 litres per second, feeding the acidic Banyupahit river, whose name means 'bitter water'.
- In 1921 Dutch colonial engineers built a dam at that breach to control the lake level and protect villages and coffee plantations in the caldera below.
- The Ijen cone that holds the lake is young: it began to form only about 2,600 years ago, inside a caldera left by a far older volcano.
- That older volcano, sometimes called Old Ijen, may once have stood about 3,500 metres high before an eruption around 50,000 years ago destroyed it.
- In the dry season from May to October the lake can drop by about four metres, and its surface sometimes grows warmer than the air above it.
- Gases dissolving in the water form sulphur spherules up to about five millimetres across, which float on the lake surface.
- During eruptions, bubbles of volcanic gas up to about ten metres across can burst through the surface of the lake.
- About ten eruptions have been recorded since 1796, and the only one known to have caused major damage and deaths was in early 1817.
Why it is worth it
Inside the crater of Ijen, in the far east of Java, lies a lake that looks like a pool of milky turquoise paint — and is one of the most hostile bodies of water on Earth. About 1 km across and up to 200 m deep, it holds some 36 million cubic metres of water so charged with sulphuric acid that measurements have recorded a pH below 0.3 in places. It is the largest highly acidic crater lake in the world, and the steam drifting off its surface stings the eyes and throat of anyone standing on the rim.
The lake sits in a crater roughly 722 m wide within the Ijen volcanic complex, which rises to 2,769 m. On its shore, vents pour out volcanic gases rich in sulphur. Where the gas meets air it can ignite, burning with flames up to 5 m high at temperatures of around 600 °C — the famous "blue fire", visible only in darkness, which is why visitors begin the climb in the middle of the night. The same gases condense into yellow sulphur, and the crater has long been worked by hand: around 200 miners break the solidified sulphur from pipes at the vents, load it into baskets of 75 to 90 kg, carry it some 300 m up the crater wall and then 3 km down the mountain. Watching them emerge from the fumes with their loads is part of what makes Ijen unforgettable.
The combination — a pale turquoise lake, a yellow shoreline, blue flames before dawn and a grey rim of rock above — makes Ijen one of the most otherworldly landscapes in Indonesia. The surrounding area was recognised as the Ijen UNESCO Global Geopark in 2023.
Getting there
The crater lies in East Java, about 19 km from Wongsorejo and some 30–35 km by road from Banyuwangi, the main town on Java's eastern tip. Bali's Ngurah Rai International Airport (DPS) is about 127 km away across the strait, but the practical gateway is Banyuwangi Airport (BWX). Visitors are driven to the Paltuding ranger post, from where a trail of about 3 km climbs to the crater rim, usually in 1.5–2 hours; the path down to the blue fire continues inside the crater.
On these lists
-8.05750, 114.24150per Wikidata