Sinkholes in Florida form when water from underground aquifers dissolves the porous limestone bedrock and pushes toward the surface. Eventually, the ground collapses into the water and an hourglass-shaped sinkhole is formed.
Florida has more springs than any other state in the U.S. Some are quite large, while others—such as Little Salt Spring—are smaller, at 243 feet (74 meters) wide. Because the spring water comes from underground, it stays at a constant temperature of 75 degrees Fahrenheit (24 degrees Celsius).
When Little Salt Spring was formed during the last Ice Age, sea level was lower and what is now the Florida peninsula was much wider. Sources of freshwater were scarce. Ancient Native Americans came to the sinkhole to drink the water and perhaps find a meal.
"Florida was much drier than it is today," Gifford said. "Essentially, [Little Salt Spring] was an oasis." Gifford and his divers worked last summer on a ledge about 90 feet (27 meters) below the surface where the stake and tortoise remains were found.
Gifford's divers will return to lower depths of Little Salt Spring soon, but will wait until their recent finds have been analyzed. They hope to eventually uncover evidence of campfires on the ledge. And because Little Salt Spring's waters contain little or no oxygen that would support bacteria that eats away at artifacts, it's possible they'll find near pristine items.
"There may be lots of stuff—basketry, woven fabrics, wooden implements—that you wouldn't otherwise find in an archaeological context," said Bruce Smith, curator of North American Archaeology at the National Museum of Natural History in Washington, D.C.
Finding fragile wooden artifacts would "open a new window" of understanding how early Native Americans lived, Smith said. "You can really get excited by it."
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