The February 2010 issue of Smithsonian has a long article about the sphinx, based mostly on observations and findings of Mark Lehner. I thought the most interesting part of the article was the followsing:

"The Sahara has not always been a wilderness of sand dunes. German climatologists Rudolph Kuper and Stefan Kröpelin, analyzing the radiocarbon dates of archaeological sites, recently concluded that the region’s prevailing climate pattern changed around 8,500 B.C., with the monsoon rains that covered the tropics moving north. The desert sands sprouted rolling grasslands punctuated by verdant valleys, prompting people to begin settling the region in 7,000 B.C. Kuper and Kröpelin say this green Sahara came to an end between 3,500 B.C. and 1,500 B.C., when the monsoon belt returned to the tropics and the desert reemerged. That date range is 500 years later than prevailing theories had suggested."

"Further studies led by Kröpelin revealed that the return to a desert climate was a gradual process spanning centuries. This transitional period was characterized by cycles of ever-decreasing rains and extended dry spells. Support for this theory can be found in recent research conducted by Judith Bunbury, a geologist at the University of Cambridge. After studying sediment samples in the Nile Valley, she concluded that climate change in the Giza region began early in the Old Kingdom, with desert sands arriving in force late in the era."

"The work helps explain some of Lehner’s findings. His investigations at the Lost City revealed that the site had eroded dramatically—with some structures reduced to ankle level over a period of three to four centuries after their construction. “So I had this realization,” he says, “Oh my God, this buzz saw that cut our site down is probably what also eroded the Sphinx.” In his view of the patterns of erosion on the Sphinx, intermittent wet periods dissolved salt deposits in the limestone, which recrystallized on the surface, causing softer stone to crumble while harder layers formed large flakes that would be blown away by desert winds. The Sphinx, Lehner says, was subjected to constant “scouring” during this transitional era of climate change."

“It’s a theory in progress,” says Lehner. “If I’m right, this episode could represent a kind of ‘tipping point’ between different climate states—from the wetter conditions of Khufu and Khafre’s era to a much drier environment in the last centuries of the Old Kingdom.”


In the new appendixes to the revised edition of Serpent in the Sky, John West says that the initial response to his argument that water induced weathering of the sphinx proved that it was carved in pre-dynastic times, was that the erosion was caused by wind and sand. After Robert Schoch and other geologists confirmed that the erosion was water induced, Lehner, among others, responded by saying that the erosion was due to groundwater leaching. West and Schoch disputed the theory of groundwater leaching based on the visual evidence of the vertical grooves cut into the sphinx and the sphinx enclosure, and the similar water erosion of the megalithic blocks used for the sphinx temple, that could not have been eroded by groundwater leaching since they are stacked blocks and not live stone. West also says that Lehner contended that all of the groundwater erosion of the sphinx occurred during an approximately 500 year period between the carving of the sphinx and the first of several repairs/renovations. West pointed out that revovation would not have stopped the erosive effects of groundwater leaching, if that was the agent, and also pointed out that the erosion of the sphinx and of the sphinx enclosure is similar, and the sphinx enclosure was not renovated. Now it seems that Lehner agrees with the original findings of Schoch that rainwater explains the erosion of the sphinx, but he says that this does not show that the sphinx was carved in pre-dynastic times because the sahara was green from rainfall until the middle of the fourth dynasty.

I thought it was pretty well established that Egypt has been desiccated since pre-dynastic times and that was why the ancient Egyptian population had concentrated solely along the Nile river in the first place. The article says that the report of a green Egypt in dynastic times comes from two climatologists who based their findings on radiocarbon dates of archeological sites. I wonder what that means? Am I the only one that questions this major adjustment in the timeline for the desiccation of Egypt?