It can be very difficult to detect an acid lake. A lake does not become acid over night. It takes many years or even decades for this phenomenon to happen.
We all know how famous Indonesia is for its volcanoes. Krakatau, one of the world's most powerful volcanoes, located in the Sunda Strait between Java and Sumatra, became well known because its eruption generated the most discernible sound ever reported: such an amazing noise that it was heard even in Perth, an Australian city situated approx. 1930 miles. The explosion was followed by the tsunamis, so more than 6 thousands of people died, mostly because of it. This eruption could be compared to an explosion of two hundred megatons of TNT, which means more than 13 thousand times the power of the atomic bomb that destroyed Hiroshima.
However, Kawah Ijen is the most fascinating Indonesian volcano (2.600m), also called the Green Crater from western Java.
It has a lake which is actually a solution made of two essential components, the strongest existing acids: hydrogen chloride and sulfuric acid. The maximum water capacity of the lake is estimated to be 36 million cubic meters.
If you look on the edge of the lake, you can see how sulfur is deposed almost every day on the volcanic gas eruptions. Similar acid lakes can also be found on other volcanoes, but the Indonesian lake is different, being the largest acid lake on Earth: it has a maximum depth of 212m. The mixture of rainfall water with gases coming from the inside of the volcano is the basic element that created these lakes. The acid lake contains: 600.000 tones of hydrogen chloride, 200.000 tons of aluminum sulfate, 170.000 tons of iron sulfate and 550.000 tons of sulfuric acid.
The acid lakes water has a beautiful turquoise color, with emerald reflexes. The environs are covered by a sulfur powder and you can see how sulfur globules move on its surface. The smell is highly flavored and disturbing, filled with sulfur dioxide. On some surfaces, sulfur pours at a temperature of 120 degrees Celsius, like shining red paths, which constantly solidify, turning lemon yellow. The volcano erupts from time to time, so industrial exploitation of the lake has not yet been planned.