Rurinuma (Goshikinuma Pond Group)

One of roughly 30 shallow ponds and marshes that form the Goshikinuma group in Fukushima Prefecture, created when Mount Bandai erupted in 1888 and a landslide blocked the valley river. Rurinuma, meaning Lapis Lazuli Pond, shifts between shades of blue, green, and milky white depending on the light. Scientists attribute the unusual color to high calcium and sulfate ion concentrations in the water, along with Drepanocladus fluitans moss growing in rare mat formations on the pond floor. Because the water is fed by an acidic crater lake upstream, almost no aquatic life or plankton survives in it.