Svartsengi, or the Black Meadows, is a region of Iceland's Reykjanes peninsula defined by the black porous rock of an ancient lava flow. For 35 years, effluent from a nearby geothermal power plant has continuously flooded a portion of the region, transforming the landscape from black to blue. The effluent, a warm mixture of seawater and freshwater drawn from geothermal aquifers, contains a variety of minerals, most notably silica, or silicon dioxide. Once discharged from the power plant, the effluent fills a shallow pool where the silica collects to form light-scattering particles that impart a bright blue color. The resulting lake, lined with a soft white silica mud and inhabited by a unique variety of microbes, is thought to confer health benefits to those who bathe in the warm waters. Although the science behind the claims is evolving, nearly 400,000 visitors each year take a dip in this unique body of water better known as the Blue Lagoon.