Salt flats (sometimes called salt pans) form by evaporation of water from brine trapped in a drainage basin. This leaves the dissolved minerals behind. But the process is very slow, taking thousands (or millions) of years. As an example, the Bonneville salt flat in Utah, covering about 45 square miles, was formed from a lake that existed abut 17,000 years ago. Sodium chloride (common salt) makes up most salt flats. But some contain potassium and lithium salts. These materials make fertilizer and batteries. Salt flats form most easily in a desert climate. As a result, Africa, South America, and the U.S. all have large salt flats. The salt flats on Tidy Island are different from these old, large salt flats.

The island’s salt flats are young, tiny, and will not last long. The surge from a hurricane created them by washing over the island in 1921. And rising sea level will soon destroy them. Much more information about Tidy Island’s salt flats is here.

A few photos of the Tidy Island west salt flat

This is the westernmost salt flat on the island. It is the best preserved of the three salt flats on Tidy Island because it is nearest to Sarasota Bay and drains more rapidly than the other salt flats. This gives it more time to dry out between spring tides. It may also be newer than the other salt flats because of a 1941 hurricane washing over only the west end of the island, which was then lower than the rest of the island.

Dead, partially buried mangroves are visible in the middle of the flats, probably caused by the 1941 hurricane depositing new sand on a community of mangroves in what was a low spot. The pattern of vegetation reflects the variation in salinity. Nothing grows in the middle of the salt flat where salinity is highest. Moving outward, plant species appear in order of their salt tolerance: first salt wort, then spartina grass, then stunted black mangroves, and then progressively taller black mangroves.

This is an old black mangrove on the west salt flat. A possible explanation is that the 1941 wash-over left the sand here too salty for the mangroves to survive.

A fiddler crab on the west salt flat defending his burrow. One claw on the male grows very large. He waves this about in the hope of inducing a female to join him in his burrow. He looks like he is playing a fiddle – hence the name.