Santorini volcanic ash found in Egypt.

Santorini volcanic ash found in Egypt

Today towns of brilliantly white houses cling to the tranquil but steep cliffs of the partially collapsed volcano called Santorini in the southern Aegean Sea of Greece. But 3,500 years ago the volcano raged with a fury at least comparable to the 1883 eruption of Krakatoa, whose blast was heard 1,500 kilometers away and whose ash cloud extended 50 km into the sky. Santorini's massive eruption may have given rise to the Atlantis legend and is thought to have destroyed the Minoan civilization on Crete, 120 km to the south.

In spite of the 13 to 18 cubic km of material ejected by Santorini, until recently no traces of the ash had been found on land south of Crete. Last week, however, at the Geological Society of America meeting in Orlando, Fla., two researchers reported the southernmost find of Santorini volcanic ash grains--microscopic glass shards--along Egypt's northern coast, 800 km southeast of Santorini.

Daniel Jean Stanley and Harrison Sheng of the Smithsonian Institution's National Museum of Natural History in Washington, D.C., discovered the ash grains in four cores taken from the banks of Lake Manzala in the Nile Delta. The researchers had searched for a year, sorting through hundreds of thousands of silt grains, before they found 12 volcanic shards. Microprobe and scanning electron microscope analyses revealed that the chemical makeup of the ash grains closely coincides with that of the ashes that cover Santorini.

Stanley and Sheng dated the grains by interpolating the radiocarbon dates of core mud layers lying 1 meter above and below the ash layers. They obtained an age of about 3,500 years, which falls right in the range of eruption dates estimated for Santorini by others. "It's right on the button,' says Stanley.

According to Stanley, the find confirms that Santorini produced a tremendously powerful blast and that the ash cloud covered a wide area including Egypt. The site of the new discovery extends the pattern mapped by previous finds in deep-seacores, indicating that the Santorini ash was carried southeast by winds. Stanley suspects that the grains found in Egypt survived because they had been dropped into a quiet coastal environment; grains dropped farther offshore were probably carried away by strong ocean currents or masked by large sediment deposits from the Nile.

The new find also adds some scientific spark to a long-standing debate among archaeologists and historians over the date of the Israelites' exodus from Egypt, for which the Bible notes: ". . . for three days there was deep darkness over the whole land of Egypt' (Exodus 10:21). Many biblical scholars have maintained that the exodus took place around 1200 B.C., while others have suggested a date closer to 1450 B.C. Stanley believes that some of the ash that darkened Egyptian skies now provides the strongest nonarchaeological evidence in favor of the latter theory by offering a radiocarbon-based date of about 1500 B.C.

Photo: Twelve grains of volcanic ash thought to have come from Santorini's eruption in 1500 B.C. were discovered in northern Egypt. The scanning electron micrograph shows one of the micron-scale grains. Researchers plan to hunt through 17 newly drilled Egyptian sediment cores for additional Santorini ash.