If you've been to San Francisco by aircraft, you may have seen a colorful patchwork of ponds along the coast. These are the Cargill Salt Ponds, which have largely been sold to the government and non-profit landowners for rehabilitation.
For 150 years, salt was one of the city's main industries. The salt mines, which covered over 15,000 acres, are now part of a huge tidal wetland restoration project. This implies that the vividly colored ponds won't stay around forever.
So, why did the salt mines produce such a vibrant landscape? It's all due to a bacteria called Dunaliella, a form of algae. The algae grows into a bright red or coral pink color due to the high salt concentration of the water. In low-salt environments, algae bloom green.
While orbiting the earth, astronauts have used the salt ponds as a visual landmark, highlighting the stunning color rainbow from space.
