A series of devastating tsunamis -- not an earthquake -- might have swept away the birthplace of the Olympic Games in ancient Greece nearly 1500 years ago, according to new findings.
Scholars have long assumed that Olympia, located at the confluence of the Kladeos and Alpheios rivers in the western Peloponnese, was destroyed by an earthquake in 551 AD and later covered by flood deposits of the Kladeos river.
Indeed the site where the first Olympic Games took place in 776 BC, was rediscovered only some 250 years ago, buried under 26 feet of sand and debris.
Systematic excavations by the German Archaeological Institute, which began in 1875, brought to light the remains of some of the finest works of classical art and architecture, such as the huge temple of Zeus. It boasted a now lost 40-foot statue of the god made of gold and ivory that was numbered among the Seven Wonders of the World.
According to Andreas Vött of the Institute of Geography of Johannes Gutenberg University Mainz, Germany, the burial of ancient Olympia "is one of the most interesting geoarchaeological mysteries in the Mediterranean world."
It is hard to explain how the tiny Kladeos River could first have buried Olympia under several meters of sediment, only to subsequently get eroded by 10 to 12 meters (33 to 40 feet) down to the flow level used in ancient times.
Vött, who is investigating the paleotsunamis that occurred along the coastlines of the eastern Mediterranean over the last 11,000 years, carried sedimentological, geophysical, geochemical and microfaunal analyses by drilling 22 vibracores at the site.
"Both the composition and thickness of the sediments we find in Olympia do not go with the hydraulic potential of the Kladeos river and the geomorphological inventory of the valley,” said Vött.
Strong evidence for repeated tsunamis came from the presence of molluscs, snail shells and the remains of abundant foraminifera (marine protozoa). The sediments were transported inland at high speed and energy, reaching Olympia although the site lies some 108 feet above sea level.
"In earlier times, Olympia was not 22 kilometers (13.6 miles) away from the sea as it is today. Back then, the coastline was located eight or perhaps even more kilometers further inland," said Vött.
In this scenario, tsunamis came in from the sea and rushed into the narrow valley of Alpheios, into which the Kladeos River flows, forcing their way over the saddles behind which Olympia is located.
Further supporting the Olympia tsunami hypothesis, is the fact that identical high-energy sediments of tsunamigenic origin were found on the sea facing side of the hills.
"Olympia documents at least four phases of high-energy flood events that obviously affected the whole valley bottom," Vött and colleagues wrote in a paper to be presented in September 2011 at an international academic conference in Corinth, Greece.
One of the high-energy flood deposits encountered near Olympia was dated to 585-647 AD. This fits "well with the earthquake in 551 AD during which Olympia is reported to have been destroyed," wrote the researchers.
According to Vött, more evidence against the earthquake hypothesis lies in the fallen fragments of the columns of the Temple of Zeus, which do not lie directly on top of each other, as expected after an earthquake impact, but are "floating" in sediment.
Mainly the result of extensive seismic activities along the Hellenic Arc, tsunamis are a frequent occurrence in the eastern Mediterranean.
The most recent mega-tsunami in the Mediterranean occurred in 1908 and was related to a devastating earthquake in the Straits of Messina in southern Italy, where than 100,000 people died.
A 30 meter-high tsunami wave was recorded in the southern Aegean in 1956.
"The evaluation of historical accounts has shown that in western Greece there is one tsunami every eight to 11 years on average," said Vött.
Lorenzi, Rossella. 2011. "Tsunamis Buried Ancient Olympics Site". Discovery News. Posted: July 12, 2011. Available online: http://news.discovery.com/history/tsunami-olympics-buried-110712.html