Sour Lake received its name from the acidic water that gives it a sour taste. It contains Sulphuric acid produced as a byproduct by bacteria which consume Sulphur, The lake gets its color from the bacteria and algae in the water.

Black Dragon's Caldron was formed in 1948 by a shift of thermal activity from Sour Lake. In addition to Sulphuric acid, this caldron contains iron sulfides which give it its black color.