Many Florida Keys visitors ask about the curious sulfur smell that permeates the Florida Keys. This is a common observation made by both visitors and residents of the island chain, and it’s an interesting phenomenon with a geological explanation.
The Florida Keys sit atop a formation known as the Florida Platform, which is composed primarily of limestone and other sedimentary rocks. Embedded within these limestone deposits are pockets of naturally-occurring sulfur compounds. As groundwater, tidal movements, and other natural processes interact with the limestone, it causes the sulfur to be released into the atmosphere.
This off-gassing of sulfur is what creates the distinctive rotten egg-like odor that is so prevalent throughout the Florida Keys. The sulfur can also leave yellow staining on rocks and other surfaces, providing visual evidence of its presence.
While the sulfur smell may be unpleasant for some, it is simply a natural consequence of the Keys’ unique geology. Residents and frequent visitors often become accustomed to the scent over time, viewing it as an integral part of the character and identity of the island chain.
So in short, the Florida Keys smell like sulfur because they are quite literally sitting on top of a giant sulfur deposit. It’s an unavoidable result of the region’s geological makeup, and something that has been part of the Keys’ environment for centuries.
Sulfur smells can also come from decomposing Sargassum seaweed, which often accumulates on beaches in the Keys and along Florida’s east coast.