Ancient Sites Beneath the Sea

Two years ago, a diver accidentally discovered a 7,000-year-old burial site 21 feet underwater, in what was once a peat bog off the coast of Manasota Beach, Florida. Archaeologists were delighted, but not surprised. They knew that Florida’s western coastline had extended about 100 miles seaward from its current location when the last ice age peaked 14,000 years ago. As sea levels rose, valuable prehistoric sites were covered by water. Finding the Manasota site may have been a lucky break, but researchers aren’t leaving their next big discovery to chance. Archaeologists say that “drowned sites” could improve our understanding of how Homo sapiens reached the Western Hemisphere, and they’re adapting high-tech tools to make that happen.

The Manasota site dates to the Middle Archaic period, 8000 to 6000 BC, when hunter-gatherers began living in permanent villages. It was a major find in the 40-year exploration of the “Florida Shelf,” which began in 1973 when archaeologist Reynold Ruppé found pottery fragments and shell mounds in shallow waters near Manasota. In those early years, a search for drowned sites involved little more than a small boat towing a diver, recalls archaeologist Michael Faught.

Today, larger boats deploy submersible robots that use multi-beam side-scan sonar. The data are transmitted wirelessly to GPS-linked onboard computers that can analyze the sea floor and underlying sediments. They can cover a lot of ground fast but at a cost that approaches $25,000 a day—far beyond the means of most archaeologists and the academic institutions that support them.

Faught, however, may find answers to this problem sooner than he thinks. Offshore wind farms, which require huge undersea surveys for permitting, are poised for rapid expansion in the next few years and could turn up more exciting archaeological discoveries along the way.