Floods Swept Ancient Nile Cities Away, Expert Says
By Hillary Mayell
for National Geographic News
|October 17, 2001|
Two cities that lay at the edge of the Mediterranean more than 1,200 years ago, Herakleion and Eastern Canopus, disappeared suddenly, swallowed by the sea. Now, an international team of scientists may have figured out the mystery of why it happened.
The researchers have concluded that the two cities collapsed when the land they were built on suddenly liquefied.
Until recently, the only evidence that they existed came from Greek mythology and the writings of ancient historians. Then, during expeditions in 1999 and 2000, a team of French marine archaeologists headed by Franck Goddio found the ruinsalmost completely intactburied on the seafloor of the Abu Qir Bay in Egypt.
Since then, there has been much speculation about why the cities disappeared so suddenly. Earthquakes, subsistence conditions, and a rise in sea level have all been suggested as possibilities.
"There are no written documents on how, when, or why these two cities went down," said Jean-Daniel Stanley, a geoarchaeologist with the Smithsonian Institution in Washington, D.C.
Stanley and his colleagues at the Institut Européen d'Archéologie Sous-Marine in Paris (the European Institute of Marine Archaeology) argue that a major flood of the Nile in the middle of the eighth century A.D was to blame. The flood, they say, triggered the sinking of Eastern Canopus and Herakleion by turning the ground beneath the cities into liquefied mud.
The collapse was sudden and catastrophic, said Stanley. "We can tell," he said, "because in both places we've found gold and jewelry, which, if there had been time, people would have taken with them when fleeing."
Gateways to Egypt
Herakleion and East Canopus once stood at the mouth of the now-extinct Canopic branch of the Nile. Built sometime between the seventh and sixth centuries B.C., as the days of the Egyptian Pharaohs were coming to an end, the cities flourished as gateways to Egypt.
Herakleion was a port of entry to Egypt that grew wealthy collecting taxes on goods being shipped upriver.
Frozen in time below the waters were many temples and statues of gods and goddesses, also attesting to the cities' role as destinations for religious pilgrims.
Until the undersea discovery, historians knew about the cities only through myth and ancient literature. Menelaus, the king of Sparta and husband to Helen, over whom the Trojan War was fought, was said to have stayed in Herakleion following the ten-year war against Troy.
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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