Friday, July 27, 2007
The Middle East region—especially coastal cities such as Beirut, above—faces an impending earthquake from an underwater fault that rumbles every 1,500 years, scientists say. A Beirut research team recently identified the fault as the likely cause of a devastating quake in A.D. 551, which struck the coast of Phoenicia, now Lebanon. Photograph by Barry Iverson/Time & Life Pictures/Getty
Major Quake, Tsunami Likely in Middle East, Study Finds
for National Geographic News
July 26, 2007
In A.D. 551, a massive earthquake spawned huge tsunamis that devastated the coast of Phoenicia, now Lebanon.
Now a new underwater survey has finally uncovered the fault likely responsible for the catastrophe and shown that it rumbles approximately every 1,500 years—which means a disaster is due any day now.
"It is just a matter of time before a destructive tsunami hits this region again," said Iain Stewart, an earthquake expert at the University of Plymouth in the United Kingdom not involved in the underwater survey.
The ample archaeological and historical evidence from the A.D. 551 earthquake indicate that it was truly a catastrophic event. The resulting tsunami damaged all major coastal cities between Tripoli and Tyr, and Tripoli was reported to have "drowned." (See a Lebanon map.)
Hitting the Jackpot
Earthquakes are common in Lebanon, but many of the faults remain hidden beneath the deep waters of the Mediterranean Sea.
Surveying the region is difficult because some of the continental shelf drops off very quickly in places, reaching water depths of around 4,921 feet (1,500 meters) only five miles (eight kilometers) from the shore.
Ata Elias of the National Center for Geophysical Research in Beirut, Lebanon, and his colleagues had a hunch that the fault responsible for the A.D. 551 earthquake would lie in this offshore region. So they did an underwater geophysical survey—and "hit the jackpot," Elias said.
By bouncing radio waves off the sea floor and studying the reflection patterns, Elias and his team were able to build a three-dimensional map showing all the lumps and bumps on the ocean bottom.
Running parallel to the Middle Eastern coast, they discovered a distinctive stepped ridge—the shape made by a "thrust" fault when one of Earth's tectonic plates shoves its way beneath another.
"We inferred that this thrust fault is the source of major earthquakes," Elias said.
The team was able to trace this fault along the coast for more than 62 miles (100 kilometers).
The findings are published in the August issue of the journal Geology.
Back on land the team found additional evidence to link this fault to the A.D. 551 earthquake. A "staircase" of platforms rising from present-day sea level shows how the land had moved upward each time the thrust fault moved.
Each time the thrust fault ruptured it lifted the coastline by around three feet (a meter), Elias said.
When the platforms were at sea level they were colonized by mollusks. But as soon as they were thrust out of the water by an earthquake the mollusks died.
By dating the mollusk shells on the raised platforms, Elias' team could determine when the thrust fault moved.
At least four earthquakes similar to the A.D. 551 quake have occurred over the past 6,000 to 7,000 years, the team found—suggesting a 1,500- to 1,750-year recurrence time for destructive quakes.
From the length of the thrust fault and the amount of uplift of the platforms on land, Elias and his colleagues estimate that the A.D. 551 earthquake must have had a magnitude of about 7.5 on the Moment magnitude scale, a more modern form of measurement than the Richter scale.
When the fault ruptured in A.D. 551, part of the the seafloor collapsed by around 5 to 10 feet (1.5 to 3 meters). This drop triggered a surging tsunami, which gained height rapidly as it pushed toward land.
Stewart of the University of Plymouth said the study is interesting, but remains cautious about blaming the newfound thrust fault for the A.D. 551 event.
"The Mediterranean has a lot of big earthquakes and there are lots of benches [platforms] everywhere. It is hard to link those benches to a particular fault," he said. (Related: "Ancient Tsunami Smashed Europe, Middle East, Study Says" [December 4, 2006].)
Nonetheless, he believes that the risk of another big earthquake occurring is very high, and should be taken seriously.
"In the past this area has had a lot of big earthquakes and tsunamis, but in modern history it has been quite quiet," Stewart said.
"We have been lulled into a false sense of security, just like we were in the [2004 Indian Ocean earthquake]."
Some of the many historical records from the time of the A.D. 551 earthquake describe the complete ruin of Berytus (Beirut), Jewel of Phoenicia, and the sea retreating one to two Roman miles, or 4,921 to 9,842 feet (1,500 to 3,000 meters) from shore, enough to ground mooring ships and uncover sunken ones.
More than 30,000 people died in Beirut alone. (Who were the Phoenicians?)
"If this earthquake and tsunami were repeated today, it would be a disaster of enormous proportions," said Sanford Holst, an author and expert on ancient Phoenicia.
More than 70 percent of Lebanon's roughly 4 million people live along the coast. The seaport of Beirut has a population of 1.5 million.
What's more, much of the country's infrastructure is also located along the coast. Major highways, electrical power stations, airports, and economic centers are all next to the sea, Elias said.
To prepare for the next big quake, many of the tall buildings that line the coast need to be reinforced to withstand earthquakes. New buildings need to be built with large earthquakes in mind. And people need to be informed.
"We need an earthquake and tsunami alert system and proper emergency plans," Elias said.
A cinder cone rises from the flank of Mount Etna in Italy. A new study says that an ancient landslide on Mount Etna triggered a series of killer waves along the Mediterranean coast from Italy to Egypt, wiping out Stone Age settlements. Photograph by J. Lowenstern/USGS
Ancient Tsunami Smashed Europe, Middle East, Study Says
for National Geographic News
December 4, 2006
A massive tsunami smashed Mediterranean shores some 8,000 years ago when a giant chunk of volcano fell into the sea, researchers say.
Waves up to 165 feet (50 meters) high swept the eastern Mediterranean, triggered by a landslide on Mount Etna on the island of Sicily, according to the new study.
The research team says the natural disaster likely destroyed ancient communities, with a series of killer waves hitting the eastern Mediterranean coastline from Italy to Egypt.
Italian researchers based their findings on geological clues and evidence of a hastily abandoned Stone Age fishing settlement in Israel.
Maria Teresa Pareschi and colleagues at the National Institute of Geophysics and Volcanology in Pisa estimated the tsunami's strength by modeling the impact of the landslide from Etna, the tallest active volcano in Europe.
The team's calculation, published in the journal Geophysical Research Letters, shows that 6 cubic miles (25 cubic kilometers) of mountainside collapsed into the sea, generating giant waves that reached coasts as far away as the Middle East and North Africa.
The waves would have reached heights of about 165 feet (50 meters) off southern Italy, the team says, with a sea surge reaching 43 feet (13 meters) swamping parts of Greece and Libya.
Smaller waves hitting coasts farther away would also have had devastating power, according to Pareschi, who led the study.
"A tsunami wave height of a few meters can penetrate deeply inland," she said.
The team estimates the tsunami would have hit a maximum speed of around 450 miles an hour (725 kilometers an hour), taking a little over three and a half hours to reach what are now Israel and Egypt.
Evidence for the natural disaster comes mainly from disturbed sediments along the bottom of the Ionian Sea to the east of Sicily.
Tsunamis are known to destabilize soft marine sediments, the team notes, leaving telltale coverings of clay deposits after they reach land.
These deposits identify Mount Etna as the source of the tsunami and discount other possible causes, such as an asteroid strike or an undersea earthquake, the team says.
The researchers also speculate that a Neolithic village just off the coast of present-day Israel was hit by the tsunami.
The well-preserved Atlit-Yam settlement, which due to altered sea levels today lies submerged, "shows evidence of a sudden abandonment" 7,000 to 8,000 years ago, the researchers write.
These signs include a pile of gutted fish that had been processed and then "stored for future consumption," which was discovered buried under a layer of clay.
Further research by the Pisa-based team will investigate whether secondary tsunamis were set off by the sediment flows triggered by the initial tsunami from the Mount Etna collapse.
Pareschi said the probability of a new big collapse on Etna is low, but she added, "the eastern sector of the volcano is sliding toward the sea, and we have to understand very well the triggering mechanisms."
If the Etna tsunami had happened today, she said, the impact would be catastrophic, because the eastern Mediterranean coast is so densely populated.
Some ten percent of tsunamis worldwide occur in the Mediterranean.
The most recent volcano-triggered tsunami was caused by a landslide on the Italian island of Stromboli in the Tyrrhenian Sea in 2002.
The volume of the landslide "was however a thousand times smaller than the Mount Etna one," Pareschi said.
A tsunami early warning system is currently being developed for the Mediterranean and the northeastern Atlantic. Due to become operational in December 2007, it will form part of a global tsunami warning system coordinated by the United Nations Educational, Scientific and Cultural Organization (UNESCO).
The measure follows in the wake of the devastating Indian Ocean tsunami, caused by an earthquake in December 2004, which struck coastlines with little or no warning.
Pareschi says the ancient Etna tsunami would have been comparable with the 2004 event, which claimed around 275,000 lives.
Who were the Phoenicians?
By Rick Gore
We know they dominated sea trade in the Mediterranean for 3,000 years. Now DNA testing and recent archaeological finds are revealing just what the Phoenician legacy meant to the ancient world—and to our own.
"I am a Phoenician," says the young man, giving the name of a people who vanished from history 2,000 years ago. "At least I feel like I'm one of them. My relatives have been fishermen and sailors here for centuries."
"Good, we can use some real Phoenicians," says Spencer Wells, an American geneticist, who wraps the young man's arm in a tourniquet as they sit on the veranda of a restaurant in Byblos, Lebanon, an ancient city of stone on the Mediterranean. The young man, Pierre Abi Saad, has arrived late, eager to participate in an experiment to shed new light on the mysterious Phoenicians. He joins a group of volunteers—fishermen, shopkeepers, and taxi drivers—gathered around tables under the restaurant awning. Wells, a lanky, 34-year-old extrovert, has convinced Saad and the others to give him a sample of their blood.
"What will it tell you?" Saad asks.
"Your blood contains DNA, which is like a history book," Wells replies. "Many different people have come to Byblos over the centuries, and your blood carries traces of their DNA. It's going to tell us something about your relationships going back thousands of years."
Wells has no doubts about the power of the new genetic techniques he is bringing to our understanding of ancient peoples. Nor does his bespectacled colleague standing beside him on the veranda, Pierre Zalloua, a 37-year-old scientist with a dark goatee and an intense passion for his Lebanese heritage. The two men hope to find new clues to an age-old riddle: Who were the Phoenicians?
Although they're mentioned frequently in ancient texts as vigorous traders and sailors, we know relatively little about these puzzling people. Historians refer to them as Canaanites when talking about the culture before 1200 B.C. The Greeks called them the phoinikes, which means the "red people"—a name that became Phoenicians—after their word for a prized reddish purple cloth the Phoenicians exported. But they would never have called themselves Phoenicians. Rather, they were citizens of the ports from which they set sail, walled cities such as Byblos, Sidon, and Tyre.
The culture later known as Phoenician was flourishing as early as the third millennium B.C. in the Levant, a coastal region now divided primarily between Lebanon, Syria, and Israel. But it wasn't until around 1100 B.C., after a period of general disorder and social collapse throughout the region, that they emerged as a significant cultural and political force.
From the ninth to sixth centuries B.C. they dominated the Mediterranean Sea, establishing emporiums and colonies from Cyprus in the east to the Aegean Sea, Italy, North Africa, and Spain in the west. They grew rich trading precious metals from abroad and products such as wine, olive oil, and most notably the timber from the famous cedars of Lebanon, which forested the mountains that rise steeply from the coast of their homeland.
The armies and peoples that eventually conquered the Phoenicians either destroyed or built over their cities. Their writings, mostly on fragile papyrus, disintegrated—so that we now know the Phoenicians mainly by the biased reports of their enemies. Although the Phoenicians themselves reportedly had a rich literature, it was totally lost in antiquity. That's ironic, because the Phoenicians actually developed the modern alphabet and spread it through trade to their ports of call.
Acting as cultural middlemen, the Phoenicians disseminated ideas, myths, and knowledge from the powerful Assyrian and Babylonian worlds in what is now Syria and Iraq to their contacts in the Aegean. Those ideas helped spark a cultural revival in Greece, one which led to the Greeks' Golden Age and hence the birth of Western civilization. The Phoenicians imported so much papyrus from Egypt that the Greeks used their name for the first great Phoenician port, Byblos, to refer to the ancient paper. The name Bible, or "the book," also derives from Byblos.
Today, Spencer Wells says, "Phoenicians have become ghosts, a vanished civilization." Now he and Zalloua hope to use a different alphabet, the molecular letters of DNA, to exhume these ghosts.
Posted by lmurx at 5:22 PM