Earthquake debris shores up evidence for lost city.
"There occurred violent earthquakes and floods. And in a single day and night of misfortune... the island of Atlantis disappeared in the depths of the sea."
This account, written by Plato more than 2,300 years ago, set scientists on the trail of the lost city of Atlantis. Did it ever exist? And if so, where was it located, and when did it disappear?
In a recent paper in Geology, Marc-Andre Gutscher of the European Institute for Marine Studies in Plouzané gives details of one candidate for the lost city: the submerged island of Spartel, west of the Straits of Gibraltar.
The top of this isle lies some 60 metres beneath the surface in the Gulf of Cadiz, having plunged beneath the waves at the end of the most recent ice age as melting glaciers caused the sea level to rise.
Geological evidence has shown that a large earthquake and a tsunami hit this island some 12,000 years ago, at roughly the location and time indicated in Plato's writings.
Gutscher has surveyed this island in detail, using sound waves reflected off the sea floor to map its contours1. His results bring mixed news to Atlantis hunters.
Ups and downs
“With the information we have from the ancient text, it may never be found, if indeed it ever existed. Floyd McCoy, geologist , University of Hawaii, Kaneohe”
At first, his conclusions seemed disappointing. At the time identified by Plato for the city's loss, the sea level would have been fairly high on the island's banks.
According to sea-level measurements alone, Gutscher estimates the island "would have been reduced to wave-swept rocky islets" and would have been less than 500 metres in diameter, making it impossibly small for a sophisticated city.
But there is a saving grace. Gutscher says the island might have sunk further since those times from seismic activity.
Layers of turbidite, the sand and mud shaken up by underwater avalanches, suggest that eight earthquakes have happened in the area since Atlantis sank. Each earthquake could have resulted in a drop of the sea floor by several metres.
So 12,000 years ago, Spartel might have been 40 metres higher than expected, and could have measured five by two kilometres.
"This is an interesting contribution to the discussion," says Jacques Collina-Girard, a geologist at the University of the Mediterranean in Aix-en-Provence, who suggested Spartel as a candidate for Atlantis a few years ago.
"This does not mean the island was inhabited," Gutscher cautions. At a conference of Atlantis researchers in Greece this month, he became convinced that the sophisticated city described by some could not have existed this long ago. "If inhabited, it would have probably been simple fishermen and not a Bronze Age culture as described by Plato," he says.
The Bronze Age is usually described as beginning just 5,000 years ago. Gutscher adds that his sound reflection data revealed no unusual geometric structures that could suggest an extinct civilization.
He says that the Egyptians who told Plato the Atlantis story may have used a different definition of 'years', meaning the destruction of Atlantis happened more recently than thought.
The conference in Greece came to no firm conclusions about the city's existence. But researchers managed to agree on 24 criteria that a geographical area must satisfy in order to qualify as a site where Atlantis could have existed. The place must have accommodated such oddities as hot springs, northerly winds, elephants, enough people for an army of 10,000 chariots, and a ritual of bull sacrifice.
At present there are half a dozen candidates for Atlantis's location, each one with its own shortcomings. Some say that settling on a final answer may prove impossible.
"The geophysics is well done, the geology excellent," says geologist Floyd McCoy of the University of Hawaii, Kaneohe, of Gutscher's study. "But most of Plato's description of Atlantis is so ambiguous and open to interpretation. With the information we have from the ancient text, it may never be found, if indeed it ever existed."
GutscherM. A., et al. Geology, 33. 685 - 688 (2005).
University of Hawaii, Kaneohe