Eerie Beauty of Kawah Ijen’s Menacing Waters: World’s Largest Acidic Cauldron Unveiled

True-color satellite image of Kawah Ijen Crater Lake, in East Java, Indonesia. It is the world’s largest acidic lake. Credit: Contains modified Copernicus Sentinel data (2023), processed by ESA, CC BY-SA 3.0 IGO

The Kawah Ijen Crater Lake in Indonesia, with its vibrant but toxic waters, is the world’s largest acidic lake. It’s known for its strikingly blue appearance and nighttime blue flames caused by burning sulfurous gases, all set against the backdrop of the towering Raung Volcano.

What’s spookier than the ‘largest acid cauldron on Earth?’ In East Java, Indonesia, lies the Kawah Ijen Crater Lake – the world’s largest acidic lake, a chilling spectacle perfect for Halloween.

Capturing Kawah Ijen from Space

The images here have been captured by the Copernicus Sentinel-2 mission which provides optical images of Earth’s surface. In the true-color image above, we can see Kawah Ijen with its striking turquoise blue waters.

Although seemingly inviting, the lake is filled with a high concentration of sulphuric and hydrochloric acids, as well as dissolved minerals. Though this deems the lake unswimmable, it makes it incredibly easy to spot from space. The water in the Kawah Ijen Crater Lake has pH values as low as 0.5, similar to the strength of car battery acid.

A Spectacle of Horror and Natural Wonder

The image below, on the other hand, takes on a horror-style palette for Halloween. It has been processed including a specific band from Sentinel-2 that is often used for coastal water and ocean color observation. By using this band combination, the Kawah Ijen Crater Lake shows a higher reflectance compared to its surroundings, with the lake’s waters appearing electric blue.

This satellite image shows Kawah Ijen Crater Lake in a horror-style palette for Halloween. Credit: Contains modified Copernicus Sentinel data (2023), processed by ESA, CC BY-SA 3.0 IGO

The lake’s unnaturally high acidity is not its sole frightening characteristic. It also emits hot, flammable sulfurous gases that ignite as they enter Earth’s oxygen-rich atmosphere. These then burn with an eerie, blue flame, creating an enchanting nighttime spectacle.

Also seen in the images is the Raung, or Gunung Raung Volcano, one of the most active volcanoes on the island of Java. With an impressive height of 3332 m (10,932 ft), it looms in the immediate southwest vicinity.