Evidence has been found that torrents of water flowing down the Mississippi River from a rapidly melting ice sheet some 11.600 years ago raised worldwide sea levels enough to explain for the many accounts of a great prehistoric flood.
Scientists from the University of Miami, reporting this in the Sept. 26 issue of the journal Science, note that the time coincides with that set by Plato for the destruction of Atlantis by flooding.
The time also matches that of a great southward thrust, or “surge.” of the North American ice sheet into central Wisconsin. Since this was a period of global warming, the surge is thought to have occurred when melting at the base of the ice enabled it suddenly to flow south and melt rapidly.
Some scientists believe similar surges carried ice into Hudson Bay and the North Atlantic off Newfoundland, contributing, to the sudden rise in sea level. According to Dr. Cesare Emiliani of the University of Miami, sea level at the start of that rise was 40 meters, or 131 feet, lower than it is today.
Hence successive beach lines and other evidence for a swift rise would now lie submerged. Dr Emiliani is an authority on the history of past climate as recorded in oceanic sediments. He is widely known for his argument that there have been eight major ice ages over the past million or two million years rather than the traditionally accepted four. He and seven other University of Miami scientists prepared the report on the sea?level rise.
The evidence was derived primarily from two cores of sediment extracted from the floor of the Gulf of Mexico on the edge of the Continental Shelf midway between Florida and the Mississippi delta.
Based on Shell Carbon
The timetable of this change was based on ages determined by measurements of radioactive carbon in the shells. The fact that it was a warm period was shown by the relative abundance of warm?water species.
In a telephone interview yesterday, Dr. Emiliani pointed out that, according to Dr. Willard F. Libby of the University of California at Los Angeles, the southward surge of ice into Wisconsin, known as the Valders Advance, coincided with the timing of 11,600 years determined for the massive discharge of fresh water into the Gulf.
Dr. Libby won A Nobel Prize for his discovery that the ages of biological samples can be determined through the extent to which radioactive carbon-14—within them has decayed. Since the organism, be it a tree or sea creature, no longer incorporates carbon 14 into its wood or shell, once it dies the extent of carbon?I4 decay is a measure of time elapsed since the death.
Similar Evidence Found
From the carbon in trees levelled by the Valders Advance. Dr. Libby was able to establish its age. Reached by phone yesterday, he said that evidence for ice advances coincident with the Valders Advance had been found in samples from Europe. South America and, reportedly, from New Zealand.
The evidence that the Valders Advance into Wisconsin coincided with a warming and massive discharge of fresh water into the gulf. Dr. Emiliani says, is “ironclad proof” of the surge hypothesis. It means, he added, that the proposition that similar surges may occur in the ice sheet of western Antarctica must be taken seriously.
It has been suggested that such surges could raise sea levels rapidly enough to result in a serious impact on coastal cities and agricultural areas.
As noted in the Science article, there are accounts of unique and catastrophic floods in the traditions, of the Americas, Australasia and Eurasia. Two of Plato’s dialogues—the Timaeus and Critias—tell of the destruction of Atlantis by flooding.
The account, according to Plato, was given to his ancestor, Solon, by Egyptian priests; who said it occurred 9,000 years in the past. Since Solon would have been alive in about, 560 B.C., this would be 11,535 years before the present.
Speculation Over Atlantis
Because the civilization of Atlantis, as described by Plato, resembles the Minoan culture of ancient Crete, some have speculate that the engulfing speculated that the engulfing the destruction of that civilization by the explosive eruption of the volcano at Thera, about 1400 B.C.
Biblical scholars have sought to reconstruct the chronology of the Old Testament and set a time for the deluge, described in Genesis. The most famous effort, by Bishop James Ussher of Ireland in the 17th century, put it at about 2350 B.C. or 4,325 years ago. The Bible itself, however, is imprecise in this regard.
It has been proposed, Dr. Emiliani said, that tales of the great flood in various traditions derived from a single catastrophe—for example in Mesopotamia—word of which then spread.
It seems improbable, he said, that it could have travelled so widely. The Navajo Indians, for example, regarded the Grand Canyon as the product of a deluge long before their first contact with Europeans.
Another proposal is that great. floods occur sooner or later in the history of every culture. Dr. Emiliani, however, believes a global sea?level rise between 11,000 and 12,000 years ago to be the best explanation.
He pointed out that the first indication of a rush of fresh water into the Gulf of Mexico was obtained by Dr. James P. Kennett of the University of Rhode Island and Dr: N. J. Shackleton of Cambridge University in England. Reporting in Science last April 11, they estimated that the torrent occurred between 12,000 and 15,000 years ago, based on cores obtained farther west in the gulf.
The new, more precise date, Dr. Emiliani said, now links the input of fresh water to the Valders Advance and a warm period. In both cases, the input was determined from a reduction in the relative amount of heavy oxygen—oxygen 18—in the sediment.
Water from melting glaciers is much depleted in oxygen 18, relative to seawater. The salinity of the gulf dropped 20 per cent, Dr. Emiliani said. Co?authors of the report were Koneta Eldridge, Dwight K. Elvey, Stefan Gartner, Ting Chang Huang. Barbara Lidz, Jerry J. Stipp and Mary F. Swanson.