It is known that three lakes at the top of the Indonesian Kelimutu volcano on Flores Island change color unpredictably - from milky white to bright turquoise and even blood red. This phenomenon is unique.
These images were taken by the OLI tool kit on the Landsat 8 satellite and show different colors of crater lakes on three different days. All three crater lakes are located on the crest of the volcano, and the two eastern lakes even have a common crater wall.
The changing colors of the lakes have inspired local folklore. Locals say that lakes are the resting places of departed souls. Depending on the good or bad deeds done in their life, the dead are placed in different lakes.
The westernmost lake, known as Tiwu Ata Mbupu (meaning "old people's lake"), is usually blue. Tiwu Nuwa Muri Koo Fai ("lake of young men and women") is usually turquoise in color. The southeastern lake, called Tiwu Ata Polo ("enchanted lake"), is usually red or brown. It is believed to be home to those who have committed evil deeds. Depending on the time, the colors can vary - white, green, blue, brown or black. In 2016, the lakes changed color six times.
Although it is known that lakes can be colored by different types of bacteria, the color changes of Kelimutu lakes are more likely associated with fumaroles - cracks that are the source of hot gas emissions. Fumaroles produce a rise in water in lakes - denser mineral water rises from the bottom to the surface. All lakes have relatively high concentrations of zinc and lead.
Minerals only partially explain the phenomenon, another key factor is the amount of oxygen in the water. Like blood, lake waters appear bluer (or greener) when oxygen levels are low. When they are enriched with oxygen, they look blood red or even black.