Vigorous black hydrothermal pool

 

This feature is one of many similar geothermal pools within the area, characterised by its deep, charcoal black colouration and vigorous activity. There is very intense heating and gas release, with geysering. The gas-charged water surges to a height of approx one meter. The dark color comes from a mix of metal sulphides – specifically iron pyrite and suspended carbons. Normally, those heavy minerals would sink to the bottom, but because the pool is constantly churning and boiling, they stay trapped in the water, giving it a thick, dark appearance.

The pool is also highly acidic (often around pH 1–2) due to hydrogen sulphide gas oxidising to form sulphuric acid, which breaks down surrounding rock into clay minerals.