Washington Report on Middle East Affairs, April/May 1992, Page 70

Science Watch

By Kurt Holden

Silence of the Sphinx May Have Lasted 9,000 Years

The theory that the Great Sphinx of Giza was created in the 26th century B.C. during ancient Egypt's fourth dynasty has been challenged by Boston University geologist and anthropologist Robert M. Schoch. In a paper introduced at the February meeting of the American Association for the Advancement of Science in Chicago, Schoch maintained that the 240-foot-long, 66-foot-high representation of a man's head on a lion's body may be twice as old as previously believed.

Schoch and a team of colleagues re-examined old evidence and used sound waves to analyze heavy weathering of the statue's base, which extends well below the surface of the ground. Unlike nearby 4,500-year-old temples, which many scientists consider contemporary with the giant statue, the sphinx was not built from rectangular stone blocks. Instead it was carved from a single limestone outcrop.

The conventional theory has been that the sphinx was left standing at stone blocks for the temples were quarried from around it. Pointing out that the temples have not suffered the heavy erosion visible on the sphinx's base, Schoch proposes instead that the sphinx was carved between 7,000 and 9,000 years ago by workers who dug into the bedrock in pre-dynastic times, between 800 and 3,000 years before the first pharoah. The blocks were quarried from around it long after its creation, Schoch suggests.

Schoch also has a theory to account for the perplexing fact that the sphinx's head shows much less erosion than its base. The Boston University scientist believes this probably results from recarving of the head in later dynastic times. Schoch's conclusions were contested by other archeologists at the meeting.

Paleontologists Plan Tunis Probe for Cause of Dinosaur Extinctions

The El Kef rock formation in Tunisia will be the site of an unusual scientific face-off between paleontologists Gerta Keller of Princeton University and Jan Smit of the Free University in Amsterdam in April. They and other paleontologists will meet to collect marine-fossil-bearing rocks from above and below a thin clay layer discernible at El Kef, as in rocks around the world, and known as the K-T boundary. The clay layer is enriched with iridium, an element rare in the earth's crust but common in meteorites.

Most scientists now agree with a theory advanced in the 1970s by a father and son team of American scientists, Luis and Walter Alvarez, that the layer represents the fallout from an immense cloud of dust raised by the impact of an asteroid of comet that struck the earth 65 million years ago. Many scientists believe the remnants of the crater created by the impact of this object from space can be traced in the Caribbean-Yucatan area.

What is in dispute in the Tunisian face-off is whether or not a tremendous die-off of land and marine plants and animals that resulted in huge numbers of extinctions occurred suddenly and almost solely as a result of this impact. Not in dispute is that the clay layer occurs at the boundary in geologic time between the rocks laid down at the end of the Cretaceous period, when the last of the dinosaurs disappeared after 150 million years on earth, and the beginning of the Tertiary period, the age of mammals, in which primates and, millions of years later, humans evolved.

Keller is among scientists who believe that the extinctions around the K-T boundary took place gradually over a period of time and probably resulted from a series of climate-altering causes, possibly including clouds of volcanic ash raised by a series of cataclysmic volcanic eruptions in India. She cites microscopic marine plankton (foraminifera) fossils from El Kef and other sites as evidence that about one-third of the extinctions of the period took place some 100,000 to 300,000 years before the hypothesized impact, one third around the time of the impact, and a final third well after that time.

Smit, however, says "there was a major crash in the oceans of 97.9 percent of all living organisms in the surface." He says that species Keller reports became extinct before the K-T boundary were living right up to the time of the impact. At the April gathering at El Kef, originally scheduled for the spring of 1991 but cancelled because of the Gulf war, the scientists will collect Tunisian samples and then exchange them with each other. None of the participating scientists will know from what points in the time sequence the rocks they are analyzing have been collected by their colleagues, until all compare their field and laboratory notes.

The results should go a long way toward settling the question of sudden versus gradual extinctions all over the planet, and the reason or reasons for them.

Kurt Holden is a documentary film producer from Southern California who divides his time between the U.S. and the Middle East.