Largest hyperacid lake
Who
Kawah Ijen crater lake
What
27,500,000 cubic metre(s)
Where
Indonesien ()
When
2011

With dimensions of approximately 1,000 x 600 metres (3,280 x 1,970 feet), a maximum depth of 200 metres (660 feet) and a volume of 27.5 million cubic metres (971 million cubic feet) – based on echo soundings taken in 2010–11 – the largest natural acidic body of water is the oval-shaped crater lake in the Kawah Ijen volcano, located on the island of Java in Indonesia. The water has a pH of less than 0, corrosive enough to eat through metal; for context, battery acid has a pH of 1. The average water temperature is 37 degrees Celsius (99 degrees Fahrenheit) – the same as human body temperature.


The lake typically has a green or turquoise hue, its colouration derived from chemicals in the water, which includes high levels of sulphuric and hydrochloric acid. Slicks of native sulphur float on the lake and include hollow spheres that represent a sulphur coating on gas bubbling up from the lake floor.

Kawah Ijen volcano plays host to one of the few remaining active artisanal sulphur mines in the world, with the sulphur forming a significant part of the local economy – despite the inhospitable and detrimental conditions to the health of those who regularly visit the site.

As well as the money raised from mining sulphur, tourism continues to grow in popularity with travellers venturing here to see the acid lake and other unusual phenomena such as billowing fumaroles and “blue lava” (what is, in fact, sulphuric gas that seeps from underground and ignites on the surface, sometimes transforming into a liquid state).

The last major magmatic eruption at Kawah Ijen occurred in Jan–Feb 1817.