for National Geographic News
Tsunamis like the the one that devastated ancient Alexandria in A.D. 365 may hit the Mediterranean relatively often, a new study argues.
Scientists say they have pinpointed the geological fault—off the coast of the Greek island of Crete—that likely slipped during a huge quake and caused the ancient tsunami.
Massive earthquakes—greater than magnitude 8—may strike the Mediterranean roughly every 800 years, the research suggests.
But other scientists say that not enough is known about these faults to predict how often such quakes might strike. They argue that the 365 disaster may have been unique.
The authors of the new study measured the remains of corals, algae, and other sea life that run in a band along the coast of Crete.
"The ancient shoreline resembles a bathtub ring high above the sea on the cliff face," said Beth Shaw of the University of Cambridge in England, lead author of the study.
The findings, published in Nature Geoscience, fix a date to when western Crete was suddenly lifted up, strengthening the tie between this event and the tsunami (see a map of Crete).
The team narrowed down the date of the uplift to within a few decades of 365, bolstering the idea that the upward shift happened in one sudden jolt.
"Ten meters [33 feet] of uplift is quite astonishing," Shaw said. "Unexpectedly, our results confirm that all [of the] uplift did happen in the 365 A.D. earthquake."
For at least 150 years, scientists have recognized that something unusual happened along western Crete.
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