Hiking an active Indonesian volcano: how to trek through the blue flames of Kawah Ijen | South China Morning Post

Hiking an active Indonesian volcano: how to trek through the blue flames of Kawah Ijen | South China Morning Post: One of the largest acidic lakes in the world, Kawah Ijen, in the crater of a volcano where sulphur miners toil, is famous for its natural blue flames, which occur when sulphur gases come into contact with oxygen.