(Image from Nasa's The Earth Observatory.)
If you've ever flown into SFO airport in daylight, you've probably seen those enormous and brightly colored pools right at the southernmost edge of the San Francisco Bay.
For years, I had wondered what they were. When I first moved to California, I remember asking people about them all the time, especially anyone who had grown up in California, and particularly while making small talk at parties. I would always described them as looking like pools of paint. Sometimes, they would be extremely different colors, traffic-cone orange or pink or green. They are magnificent, but also a unsettling, as surely they are not natural. You can't miss them. Most of them are bigger than a football field.
One person I met was sure they were cranberry bogs. Another suggested it was a sewage treatment facility, and that the different colors represented a different chemical stage in the process, which was the answer I had entertained momentarily before thinking, "But why are all the pools exposed to open air? Isn't that dangerous?"
Just the other day, I finally, and quite accidentally, came across the truth.
They're salt ponds.
I was reading the last chapter of Michael Pollan's The Omnivore's Dilemma, in which he describes a grand meal that he is going to prepare for his family and friends who have helped to write the book by teaching him how to forage, hunt, and do other back-to-nature culinary tasks. His goal is for nearly everything served to have been a product of his own toil in some way. He's also looking to satisfy the last leg of the animal-vegetable-mineral trinity by putting self-scrounged salt on the table. And there it was (page 393):
"...I had learned that there are still a few salt ponds at the bottom of San Francisco Bay. You can see them flying into SFO, a sequence of arresting blocks of color -- rust, yellow, orange, blood red -- laid out below you as if in a Mondrian painting. The different colors, I learned, are created by different species of salt-tolerant algae and archaea; as the seawater evaporates from the ponds, the salinity rises, creating conditions suitable for one species of microorganism or another.
"After an interminable trek through acrid and trash-strewn wetlands, we found the salt ponds: rectangular fields of shallow water outlined by grassy levees. The water was the color of strong tea and the levees were littered with garbage: soda cans and bottles, car parts and tires, hundreds of tennis balls abandoned by dogs."
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