West of Gunung Merapi is the Ijen volcano, which has a one-kilometer-wide turquoise-colored acidic crater lake. The lake is the site of a labor-intensive sulfur mining operation, in which sulfur-laden baskets are carried by hand from the crater floor. The work is paid well considering the cost of living in the area, but is very onerous. At the left of the frame a blue flame from exploding gasses can be seen.