Blue Pond, Biei, Hokkaido, Japan
It’s an artificial pond created when a dam was erected to protect the region from mudflows that might occur from the nearby volcano on Mt. Tokachi. The blue color of the pond has not been fully explained but is attributed to the presence of aluminum hydroxide in the water that reflects the shorter wavelength blue light the same way the earth’s atmosphere does. The color of the pond also changes depending on what angle you look at it from and even at different times of the day. Although the water appears blue when viewed from the land, the color is not found in the water itself. 

Blue Pond, Biei, Hokkaido, Japan

It’s an artificial pond created when a dam was erected to protect the region from mudflows that might occur from the nearby volcano on Mt. Tokachi. The blue color of the pond has not been fully explained but is attributed to the presence of aluminum hydroxide in the water that reflects the shorter wavelength blue light the same way the earth’s atmosphere does. The color of the pond also changes depending on what angle you look at it from and even at different times of the day. Although the water appears blue when viewed from the land, the color is not found in the water itself.