Photograph by Howie Goodman
To almost anyone else, the broken shells would look like…broken shells. But Dr. Beverly Goodman stares at the shattered fragments and sees an ancient tsunami. What's more, the mysterious story she coaxes from the two thousand year-old remnants may also predict the future.
Goodman blends skills from archeology, geology, and anthropology to explore the complex ways nature and humans interact on coastlines. "Analyzing the causes and effects of ancient environmental events like tsunamis can help tell us which types of coasts are at greatest risk, and what kind of damage to expect in the future," she explains.
As coastal populations increase exponentially, and sea levels continue to rise, the information she gleans becomes ever more crucial. "No place is more vulnerable than our coasts. We can either make responsible choices, or face enormous repercussions."
The physical evidence her team collects and analyzes helps to reveal the causes and frequency of tsunami events. "Was it caused by a volcanic eruption? An underwater earthquake? A deep sea landslide? Did it occur every 5,000 years, or far more often? Those answers can help predict and perhaps even monitor dangerous events along today's coasts," she notes.
Goodman's fieldwork centers in Caesarea, Israel where Herod the Great built a massive harbor at the end of the first century B.C. Her team's findings prove that a tsunami struck the ancient harbor sometime in the first or second century A.D., and likely caused its destruction. Written records exist, but until the team's discoveries, virtually no physical evidence had been found to corroborate historical texts. "Relying on texts alone can be unreliable," she points out, "because many of those records are actually requests for help, and often exaggerate the extent of damage."
The tsunami studies that now consume Goodman began quite by accident. She originally came to Caesarea to help explore the harbor's ancient design and construction. While investigating suspected shipwreck sites just outside the harbor, her team found a typical layer of ceramics and stones. Then they did what geologists do: dig deeper. "All of the sudden we hit a massive shell deposit," she remembers. "Instead of a normal half-inch layer, this band of shells was more than three feet thick! Totally unlike anything we'd seen here."
The first core sample was taken, launching years of still-ongoing collection and analysis. Layers within core samples can be read like the rings of a tree. Carbon dating revealed the entire deposit was the same age—indicating a single, rapid, violent, event. And since almost all shells were broken, they had clearly been transported from somewhere else. From the position of the shells, the team could estimate the level of energy which had carried them. The puzzle was coming together, and every piece fit the unmistakable profile of a major tsunami event.
Goodman's Caesarea explorations produced not only important new information, but a new way to gather it. "Coring in very shallow or deep water is fairly straightforward," she observes. "But in the upper shelf zone where we work, it's very difficult. The sand is much harder to penetrate." To overcome the problem, she helped develop a new coring technique, allowing effective collection at this depth for the very first time.
Underwater finds such as this often yield richer information than land deposits. "Even in places regularly hit by tsunamis, people don't leave," she says. "They clean up, rebuild, and most evidence is erased. Underwater, you don't find that same degree of human disturbance and influence. We get a much more accurate picture."
Soon Goodman plans to "take our method on the road," performing excavations throughout the Mediterranean. The expedition will gather and study core samples from several offshore archeological sites, seeking to connect the dots and show a pattern of tsunami activity across the region.
"Our fieldwork requires massive planning," she says. "But that's all on paper. Then suddenly it's time to put on your wetsuit and it's not theoretical anymore. When the first core goes in and everything succeeds, there's a big adrenaline rush, and huge relief. Coastal regions present one of the major challenges of our time. I hope I'm collecting clues that will help us avoid catastrophic consequences down the line."
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In Their Words
Coastlines are the most dynamic natural environments on earth. We need to understand where to build, what to anticipate, and how to avoid disasters.
National Geographic Explorers Christina Conlee and Beverly Goodman investigate past tsunami sites and save treasures.
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