When Gilad Shtienberg began digging on an Israeli beach in August 2018, the last thing he expected to find were seashells. Boring some 9.14 m below the sandy surface, Shtienberg, a geomorphologist at the Scripps Centre for Marine Archaeology in California, was excavating a doorknob-shaped cove called the Bay of Dor. Nearly 10,000 years ago, the cove was part of a marshy wetland at least a mile (1.6 km) inland from the coast. So it was befuddling when he found evidence of marine life staring back at him in the sediment cores; a taupe strip in an otherwise-umber soil sample, evidence of a tsunami sandwiched within layers of the Neolithic Levant.
“A borehole is like a peephole to the past,” Shtienberg told Gizmodo, “because we can use the sediments that are acquired inside of these plastic tubes to get an understanding of how the environment changed over time.” Shtienberg is lead author of a new paper on the excavations, published today in the open-access journal PLOS One.
More than 60 holes were bored in the area of Tel Dor, a large mound of human settlement dating back to the Middle Bronze Age, which lies about halfway between the Roman ruins at Caesarea and the Crusader fortress at Atlit. Cored sediment samples kept turning up that beige strip of marine critters, suggesting whatever force brought the shells inland was widespread. “By the fifth core, I was sure that we had something,” Shtienberg said.
The research team, funded by the Koret Foundation and hailing from the University of California, Utah State University, and the University of Haifa in Israel, used optically stimulated luminescence technology to date the quartz-heavy mineral deposits from the beach. (The somewhat-better-known radiocarbon dating doesn’t work well on the beaches in the area, Shtienberg said, due to the large margins of error in measuring carbon isotopes from marine creatures). The technology detects the last time quartz was exposed to light — i.e., right before it was buried — and narrowed the event’s timeframe down to the eighth millennium BCE. Based on the location of the cores and how far west the ancient coastline was, the team estimates the tsunami was over 15.24 m high and may have swamped the shore up to 2 miles (3.2 km) inland.
“The study is very exciting because it adds another example of physical evidence of a paleotsunami event along the Israeli coastline,” Beverly Goodman, a marine geoarchaeologist at the University of Haifa who wasn’t involved with the recent study, said in an email. “The more events that are added to the catalogue, the more complete our understanding of tsunami risk in this region becomes.”
Goodman said the team provided convincing evidence that a tsunami did indeed hit the area — though its scale is uncertain, as the Levantine coast is relatively linear and prone to erosion, so the cored tsunami evidence only cropped up around the Bay of Dor. It’s uncertain how far and up and down the coast, the wave may have reached; whether it would have rushed ashore to the north in what are now Syria and Lebanon, or to the south, in what is now the Gaza Strip.
Goodman was more sceptical about the team’s claims as to the wave’s size and impact on humans, since it’s not totally clear what Neolithic settlement of the coast looked like. “The suggestion that it was a ‘megatsunami’ will require further work,” she said.
The eastern Mediterranean may not seem like a typical venue for a tsunami; it’s far from the famous fault lines and tectonic plates that have caused diluvian situations from Northwest Washington to Southeast Asia. But the telltale seashells of Tel Dor breathe life into the notion that ancient Levantine communities were similarly vulnerable, and the tsunami may have obliterated coastal settlements, prompting an inland migration that defined habitation of the area for centuries to come.
“Societies were transitioning from over a million and a half years of being foragers and hunters in the Middle East; they were experimenting with this village-based sedentary lifestyle,” Thomas Levy, an archaeologist at UC San Diego and a co-author of the recent paper, told Gizmodo. “These communities along the Carmel coast were wiped out, essentially, and their ecosystem right along the coastal plain was destroyed and disrupted by the tsunami.”
The largest source of earthquakes in the Middle East is the Dead Sea Transform, which runs under the Jordan River Valley and splits the African tectonic plate from the Arabian plate. The team’s current hypothesis is something of a domino effect, where an ancient quake in the Dead Sea Rift beget quakes in smaller faults closer to the shore, which beget underwater landslides, which in turn pushed a massive wave onto the western shore of the area, inundating its Neolithic inhabitants.
It’s hard to say what sort of living situation existed around what is now the Bay of Dor, Levy said, because objects from the Neolithic older than 10,000 years don’t turn up in the area — perhaps reinforcing the team’s theory, as a massive wave would’ve wiped out Neolithic settlements. Later populations on what is now Israel’s Carmel coast built seawalls to keep the water at bay, though those failed in time with the relentless march of sea level rise. Other groups moved inland, into the Jordan Valley and the Carmel mountains.
“The communities living around Dor on the coastal plain that were affected by this — they’re emblematic of some kind of settlement process,” Levy said. “By the Middle Neolithic, pre-pottery Neolithic, there’s an explosion of settlements in the inland areas of the southern Levant.”
Life took time to return to Tel Dor after the tsunami washed away fertile soil, effectively salting its fields and preventing its settlement immediately following the disaster. But return it did, as evidenced by late Neolithic structures and ceramic finds in shallow water just off the coast. It’ll take some doing to excavate, though, as it lies among the breakers, meaning archaeologists have to deal with the constant crash of waves as they work.
“We’re trying to develop a methodology for excavating in this shallow surf zone,” Levy said. “Some days it’s like being in a washing machine.”