Kawah Ijen volcano, Indonesia, satellite image. Located on the island of Java, Kawah Ijen has a volcanic crater that emits hot sulphurous gases that precipitate into sulphur. Miners extract this sulphur to make products such as white sugar and matches. Kawah Ijen also has a turquoise-coloured caldera lake. The lake's bright colour is due to the extreme acidity and high concentration of dissolved metals in the water. Image obtained by a Pleiades satellite on 29th April 2018.