Soda lakes are the favoured environment for flamingos, which – in the words of the Kenya Birds organization – enjoy standing in boiling caustic soda. They have a high concentration of dissolved alkalis, mainly sodium hydroxide. But how did they get that way?
Susan Baumgarte of Brunswick Technical University in Germany points out that such lakes are not unique to the Rift Valley of East Africa. Soda lakes and soda deserts can be found from Hungary to the US. They tend to be in places with unusual geology, where sodium and potassium dominate the metals dissolved in water. Both of these metals, unlike the more usual calcium or magnesium, produce soluble alkaline compounds that can be concentrated in water, as they are not removed by evaporation. They also occur most often in hot places and usually lose water only by evaporation, not through rivers. Some have sodium salts in such abundance that they can be mined industrially.
A soda lake's pH can be as high as 125 – in other words, they are very alkaline. But despite the hostility of this environment, they are brightly coloured with bacteria and other microfauna and flora. Some of these bacteria can even chew on denim, and have been used in the chemicals that create that pre-worn look in jeans. At the time of writing this was the subject of a legal action between the manufacturers and the Kenyan Wildlife Service.
Naturally, this abundant food supply is not going to go to waste. Hence the flamingos'enthusiasm for standing beak-down in such waters all day.