What are these red pools?

Every fly into the SF Bay Area? Ever notice those bright red, green, and orange pools in South Bay? Ever wonder what they are? Check it out: they're salt flats.

A local company has been making salt in the Bay Area since the mid-19th century. The original harvesting methods included an 8-guage "portable railroad." During WWII, their salt dredging ship was used to fish spent artillery shells out of the bay. After WWII, they produced 1.3 million tons of salt per year, including almost all the salt consumed by Japan.

Now they're much smaller, due to economic changes and new technology that lets them harvest more salt on less land. So they've given the entire 40,000 acre site to the State of California and have turned it into a wildlife preserve. They still operate about a third of the area as a functioning commercial salt flat, even though it's a wildlife preserve.

What about the colors? Well, the light green is relatively fresh sea water. They pump the brine from one pond to another during the process. As the salt content increases, the fish die out and are replaced with brine shrimp. (The shrimp are also harvested and used in fishing.) The shrimp turn the pools orange and red. When the salt content gets too high, the shrimp die off and are replaced by algae. The algae actually change color and become deep red. Then it's evaporated, leaving fields of pink salt. (The red liquid is also harvested and used to clean highways.)

Here are some fun links:

• Google Earth Community: What are these red pools? (With a link to the location in Google Earth)
• Cargill Salt home page, with explanations of the different colors and a virtual tour