A mega-tsunami slammed into what is today Israel’s northern shore nearly 10,000 years ago, reaching a height of up 40 meters and traveling inland for kilometers, researchers have discovered.
This massive wave would have wiped out prehistoric villages along a segment of the coast and might explain why archaeologists have found no evidence of habitation in this area for a span of millennia during the early Neolithic.
These finds serve as a warning that such events can be surprisingly frequent, and devastating, even in a relatively small, all-but-closed sea like the Mediterranean, experts say.
A team of archaeologists and geologists from the University of California San Diego and the University of Haifa uncovered evidence of the prehistoric cataclysm at Tel Dor, an ancient seaside settlement just south of Haifa.
They were not actually looking for evidence of a tsunami but were analyzing the geological history of the area to understand environmental changes and how they influenced life at Dor, explains Gilad Shtienberg, a geoarchaeologist from UC San Diego who is the lead author on the study.
High as a 12-story building
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While the town of Dor was founded around 2000 B.C.E., the researchers drilled down into the local beach to extract sediment cores going further back in time.
Some of the oldest sediments, dating from 15,000 to 7,800 years ago and buried at a depth of up to nine meters (30 feet), consisted of dark silt and clay typical of freshwater or brackish wetlands.
This was not unexpected since in prehistoric times sea levels were lower and this area, which is now a beach, would have been a few kilometers inland. But Shtienberg noticed something strange: sandwiched between the long sequence of dark sediments was a lighter layer about 20 to 30 centimeters thick, consisting of sand and fragments of seashells.
“This is strange because we are not supposed to find sand trapped inside clay like that,” he recalls. “So I was like, wow, this is something.”
The find was not a fluke, because other sediment cores taken along Dor beach showed the same layer, dated to between 9,900 and 9,300 years ago.
The only possible explanation for the presence of these marine materials so far into a freshwater marshy environment is that they had been transported there by a tsunami, concludes Prof. Thomas E. Levy, who co-directs the marine archaeology center at UC San Diego. It can often be difficult to distinguish whether anomalous sand layers have been deposited by tsunamis or violent storms, but even the most extreme storm surge can only travel a few hundred meters inland, Levy says.
In this case, the researchers estimate that the seashore would have been between 1.5 and 3.5 kilometers away (0.9 to 2.2 miles) at the time when the layer of sand was deposited. For it to travel so far, the tsunami would have had to rise to a height of 16 to 40 meters – or something between a five and a 12-story building, they report.
Those figures are similar to wave heights experienced in the 2004 Indian Ocean tsunami, the most devastating in recorded history, which killed more than 200,000 people. Of course, that event affected thousands of kilometers of coastline across South Asia and East Africa, while the tsunami detected at Dor likely had a more limited impact.
How limited we don’t exactly know. Dor was purposely chosen for the study because the site includes a series of protected bays, which are rare in Israel’s fairly linear coastline. Elsewhere, the telltale sand layer has probably been eroded long ago by the sea, so it is difficult to determine how wide the affected area was, Shtienberg notes.
Depending on the mechanism that generates them, even large tsunamis don’t necessarily propagate along a large swath of coastline, explains Beverly Goodman, head of the marine geosciences department at the University of Haifa and an expert on ancient tsunamis. “One area of a coastline could be highly impacted during an event while a few hundreds of meters away from that zone the effects are barely felt,” says Goodman, who did not take part in the Dor study.
Mind the gap
Wherever it did hit, the Neolithic mega-tsunami must have had devastating effects, Levy says. It may in fact explain why Israel’s norther coastal plain displays a “settlement gap” of about 4,000 years right around this time.
While evidence of human activity is pretty much continuous on the higher ground, on the Carmel ridge that runs along the shore, the coast itself shows signs of habitation at the end of the Paleolithic, before 12,500 years ago, and then again 8,500 years ago in the late Neolithic – but pretty much nothing in between.
This could mean that the tsunami wiped out any evidence of preexisting settlements and damaged the local ecosystem to the point that it took centuries until people returned, Levy tells Haaretz.
Artifacts and buildings from the area’s revival in the late Neolithic have been uncovered offshore at Dor during this latest study, as well as in earlier underwater digs at sites like Atlit Yam, once a large prehistoric settlement just bit further north on the Carmel coast.
All these sites were abandoned again and permanently submerged around 7,000 years ago as melting glaciers and icecaps led to a global rise in sea levels.
As for the cause of the mega-tsunami at Dor, researchers suggest that it may have been caused by an earthquake along the very active Dead Sea Fault – the source of most temblors in present-day Israel as well.
Damage to a nearby cave in the Carmel ridge has previously been dated to around 10,000 years ago, suggesting that there may have been a strong earthquake in the area that caused a massive underwater landslide near Dor, triggering the tsunami, Shtienberg and colleagues write. Scarring on the seabed left by such a landslide has indeed been identified at a depth of around 200 meters some 16 kilometers west of the site, they report.
It will happen again
Whatever the cause of this particular event, the new research adds to our growing understanding of the frequency and impact of tsunamis on human civilizations and the lands they are built on. For example, mega-tsunamis are believed to have contributed, along with rising sea levels, to the final submersion of Doggerland, a low-lying region that connected mainland Europe to Britain until around 8,000 years ago.
The Dor event is the oldest tsunami documented so far in the Mediterranean – which doesn’t mean such events didn’t happen earlier, just that we haven’t found the evidence. For later years, no less than 23 tsunami deposits from the past 6,000 years have been detected along the Eastern Mediterranean coasts, the PLOS ONE article notes.
Some of these events, like the wave that hit Phoenician settlements along Israel’s northern coast in the 8th century B.C.E., are only known through geology and went unrecorded by history. Others, such as the tsunami that ravaged the Nile Delta in 365 C.E., have left us with vivid accounts of the death and destruction wrought by the wrath of the sea.
As he investigated the Dor tsunami, Shtienberg acknowledges that he did not expect a closed basin like the Mediterranean could produce such a massive wave.
“Imagine if something similar occurred today on the coast of Israel: we have to be prepared because it could definitely happen again,” he says.
“The more events are recognized, the more awareness and preparation we can have to avoid major loss of life and make the best coastal management decisions today,” Goodman concurs. “Paleotsunami event discoveries can help save lives today.”