Greek mythology holds that the city of Canopus was named after Menelaus' helmsman, who was bitten by a viper and transformed into a god.
The Greek historian Herodotus wrote of having visited the cities in 450 B.C.
The cities' fortunes declined when Alexander the Great founded Alexandria in 331 B.C. Yet centuries later, Greek geographer Strabo (63 B.C.-A.D. 21) described the location and wealth of Herakleion, while Seneca (5 B.C.-A.D. 65) condemned the cities for decadent and corrupt lifestyles.
The cities disappeared mysteriously sometime during the eighth century A.D.
Dating a Disaster
The cities were found at depths of 20 to 23 feet (6 to 7 meters) below the waters of Abu Qir Bay. The ruins of Eastern Canopus are nearly 1 mile (1.6 kilometers) east of the Aku Qir headland; Herakleion rests more than 3 miles (5.4 kilometers) from the shore.
Stanley and his team studied cores from the seafloor, high-resolution seismic profiles, and the composition of the substratelayers of mud, shell, silt, and sand deposited over time. From their analysis, they concluded that the cities fell when a flood caused the land to suddenly liquefy into mud.
Two Arabic coins found at the site date from between A.D. 724 and 743. Written records that document a major flood of the Nile in A.D. 741 to 742 provide a framework for dating the disappearance of the two cities. There are no major earthquakes documented for this period.
Significant flooding not only would cause the river banks to collapse, but also would bring heavy loads of sedimentation. This combined with the weight of the roiling water could have caused the soft, unstable mud on which the cities had been built to liquefy, Stanley and his colleagues argue in Volume 412 of the journal Nature.
The authors note that similar processes have occurred at the mouth of the Mississippi River.
"River mouths shift over time," Stanley explained. "It's been very common after bigger floods for the mouth of the Mississippi to change drastically. You have liquefaction, slumping riverbanks, and parts of land going up and down all over the place."
"Even offshore, two weeks after a major flood," he added, "you can have areas that were underwater suddenly above water and other areas that were above ground completely underwater."
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