Lessons from shell mound
When Hurricane Helene tore through the Southeast in September 2024, it didn’t just upend lives and landscapes, it scattered pieces of history. As one of the deadliest storms on record, Helene reshaped entire communities, including those in Florida’s Big Bend. Just miles from where the storm made landfall stands a site that has endured more than a thousand years of change, until Helene came ashore.
Located just a few miles north of Cedar Key, at the southern end of the Lower Suwannee National Wildlife Refuge(opens in new tab), lies the Shell Mound archaeological site. Composed of an estimated 1.2 billion oyster shells, the mound itself is perched atop and alongside the southern arm of a parabolic dune. Oysters were a staple food for Native Americans living in this area, a resource archaeologists think they improved and maintained. They also used the shells of oysters to construct a ridge extending south and east of the dune arm to create a crescent-shaped mound the size of two football fields. Between approximately 400 and 650 CE, when the mound was constructed, only about a hundred people lived at Shell Mound, but they occasionally hosted large gatherings of people from across the region. These gatherings resulted in archaeological traces that bear relevance to the challenges of coastal dwelling today.
Shell Mound is a fascinating site for archaeologists, especially those seeking deeper insights into Indigenous experiences with climate-related events like hurricanes. Hyatt and Cici Brown(opens in new tab) Professor of Florida Archaeology Ken Sassaman has been leading UF’s research efforts there for years, funded by an endowment created by Hyatt (BSBA, Business ’59) and Cici Brown in 2009. This endowment supports research into the ancient cultures of Florida, coastal lifeways, circum-Caribbean connections, wet site archaeology and ecological sustainability.
A place for gathering, renewal and connection
There were once several such sites of regional gatherings (known to archaeologists as “civic-ceremonial centers”) along the Gulf Coast, but what made Shell Mound particularly interesting both to those who settled there and those studying it today was its relationship with the summer solstice. Molded by Ice Age winds, the dune on which Shell Mound was built, like most dunes in the area, was aligned with the rising summer solstice sun. The ritual calendars of many Indigenous people, including those in Florida, were structured around the annual cycle of the sun. Certain ceremonies were timed to coincide with key solar events, such as the summer solstice, when it rises and sets at its northernmost point on the horizon. Sassaman and his students have compiled substantial evidence suggesting that people gathered at Shell Mound during the summer solstice for communal events, eating mullet and other fish caught in a nearby tidal trap. Sassaman believes these yearly gatherings were meant to restore balance to a world unsettled by climate change.
Aligned with the solstices, dunes of the area held deep spiritual meaning long before any civic-ceremonial centers had been built. Around 4,500 years ago, Indigenous Floridians began creating burial sites for their ancestors at the ends of dune ridges that pointed toward the place where the sun set on the winter solstice, which was the opposite point of the summer solstice sunrise. Like many other ancient cultures, they likely viewed life and death as parts of a continuous cycle. Their ancestors, they believed, hadn’t vanished but continued as members of their communities to provide wisdom and guidance for future planning.
“Ancestors are critical because they are still active in the lives of the living and curate memories that provide long-term perspective on change,” Sassaman said. “We suspect that ancestors interred in the nearby cemetery, as well as others, were active participants in summer solstice feasts and world renewal.”
Indigenous Floridians also practiced reciprocity, a social norm that encourages one to give back to others, both human and nonhuman, in exchange for the gifts they provided. It encouraged working toward the common good and brought people together to forge mutually beneficial relationships. Reciprocity applied not just to people, but also to the land itself, and they believed that giving back to the planet (Mother Earth) would help maintain balance in the planet’s natural cycles. Rituals like the ones that took place at Shell Mound were reciprocal, held for purposes of world renewal.
Shell Mound’s significance extends beyond its use as a religious site. Neutron activation analysis of pottery conducted by UF researchers suggests that Shell Mound attracted visitors from across the state and even from areas in southern Georgia. People traveled far and wide to participate in these world renewal ceremonies, and in the process, facilitate the dissemination of knowledge and ideas. They also created a sense of unity, fostering large and complex social networks that served as safety nets and helped identify friends, allies, and kin.
Sassaman calls this the predigital equivalent of Facebook. “Gatherings at Shell Mound, and other similar sites, created and reproduced interpersonal connections among people who were otherwise dispersed across the region,” he said.
Even after Shell Mound was abandoned around 650 CE, it is believed that the social networks forged by its rituals persisted long after but eventually faded or took on a new form. Shell Mound’s inhabitants didn’t die off but instead left to find a new home farther inland. In this sense, the creation of social networks enabled by gatherings at Shell Mound succeeded in affording options to relocate from the coast when local conditions soured.
Floridians are no strangers to severe weather events, whether it be hurricanes, floods, or tornadoes. Indigenous Floridians like those who lived at Shell Mound were no different in this regard, and their culture was also shaped by these catastrophes. Just as their views of life and death were cyclical, they likely understood weather as part of long-term natural cycles that extended beyond the yearly seasons. However, rare and powerful events, such as Category 5 hurricanes, disrupted these predictable patterns. Such disruptions may have prompted Indigenous communities to perform rituals aimed at restoring balance to the world.
It was one of these extreme events that Sassaman believes triggered the start of the summer solstice gatherings. Before Shell Mound’s residents first set up their civic-ceremonial center, the area around the mound was simply a peninsula, and at the tip of the peninsula was an ancestral cemetery. About 1,800 years ago, a major climate event or series of events eroded nearby shorelines along the Gulf Coast to enable the sea to transgress about 2 kilometers inland. The higher water cut off the cemetery from the rest of the peninsula, leaving it stranded on a freshly formed island 500 meters west of Shell Mound.
By that time, Indigenous Floridians had been burying their ancestors in that cemetery for about 900 years, and the relatively sudden cut-off from that land was likely a major existential crisis for them. Something had separated them from their ancestors, and many of their collective memories were tied to the land on which they were buried. According to their belief in reciprocity and co-creation, a large event like this one would require rebalancing, leading to the start of yearly solstice rituals. “The gatherings and feasts continued for 200-250 years until the sea regressed during a period of global cooling and coastline regression, reconnecting Shell Mound with the ancestors,” Sassaman said. “One could read this as a successful rebalancing.”
Although Shell Mound has stood abandoned for many centuries, there is still much we can learn from the place and its people. Even without the advanced meteorological equipment we use to forecast major weather events today, Indigenous Floridians were prepared for hurricanes and were able to quickly bounce back from these destructive events.
“What we call Traditional Ecological Knowledge arises from experience that is accumulated and passed along through practice,” Sassaman explained. “The longer the time-depth of knowledge, the better able to deal with low-frequency but high-magnitude events that disrupt life.”
We can see this in the structure of Shell Mound, which demonstrates how they worked with the natural environment to prepare for extreme weather. They built their community next to a hill and constructed a shell ridge to create an enclosure, creating a buffer between themselves and the water, and they used their discarded oyster shells to make parts of the hill even taller to help protect themselves from the strong winds. Evidence also suggests that this terraforming effort was done relatively quickly, with the south ridge being constructed around 500 AD from the north ridge’s extant shell deposits. They had a multi-generational perspective and prepared not just themselves but their descendants to endure these extreme weather events.
What shell mound teaches us now
After Hurricane Helene dissipated, a team of UF archaeologists and U.S. Fish and Wildlife staff returned to Shell Mound to assess the damage. Restoration would be no small feat and was done in collaboration with Friends of the Lower Suwannee and Cedar Keys National Wildlife Refuges. Sassaman additionally enlisted the help of several anthropology students, including graduate student Lukas Desjardins.
“My work at Shell Mound is part of my master’s project,” Desjardins said. “I was interested in researching how archaeological sites were impacted by climate change, so when Dr. Sassaman asked if anyone wanted to join him in the restoration efforts, I volunteered.”
Their work began with researchers mapping the area using a scanning method called Light Detection and Ranging, or LIDAR for short. LIDAR scanning uses drone-mounted lasers to shine beams onto surfaces, measuring the length of their reflections to create detailed 3D scans. These scans were conducted by UF Associate Professor of Forest Ecology and Geomatics Eben Broadbent, and his GatorEye Unmanned Flying Laboratory, which had previously created another 3D scan of Shell Mound back in 2018.
Now armed with a scan from before Helene and one from after, Desjardins used a mapping visualization program to begin comparing the two. Altogether, about 540 cubic meters of shell were displaced throughout Shell Mound, enough to fill up about a fifth of an Olympic-sized swimming pool. Very few areas were left untouched, but a significant portion of these damages occurred in areas that had already been impacted by previous human activities.
There were three main areas: the north ridge alongside the road to the parking lot, the west edge closest to said parking lot, and an area on the south end that had been mined out for shells during the 19th and 20th centuries. Desjardins hypothesizes that this pattern is a result of elevation, as each of these areas has a higher slope than surrounding areas and thus received more energy from the storm surges and winds that crash into them. Despite severe damage to exterior areas, the plaza inside the crescent-shaped mound was left relatively untouched, protected from storm surges and roaring winds by the natural and man-made barriers.
Once the most damaged areas were identified, restoration efforts began. In July 2025, a mix of displaced shells gathered from the road and crushed limestone was spread along the hardest-hit areas of Shell Mound’s south ridge.
“The hope is that after a few rains, once the material settles, it will begin to harden and create a more durable surface to survive future storms,” Desjardins said. “By re-creating a more natural slope on the south ridge, wave energy will be better attenuated during storm surges, and waves will be less likely to undercut the site.”
The road to recovery remains long, but he hopes their work will help Shell Mound emerge stronger, continuing to stand as a testament to the past and a potential touchstone on coastal sustainability for generations to come.