EROSION PROCESSES ON THE GREAT SPHINX AND ITS DATING

Many recent Egyptologists have attributed the carving of the Great Sphinx of Giza to the Old Kingdom Pharaoh Khafre (Chephren), ca. 2500 B.C. On the basis of a number of lines of geological, seismological, Egyptological, and related evidence, I have come to the conclusion that the structure commonly known as the Great Sphinx was built in stages (originally it may not have even been a Sphinx).  Initial carving of the core body of the Sphinx is estimated to have taken place during the period of approximately 7,000 to 5,000 B.C.  The Sphinx has subsequently been reworked and refurbished many times over the succeeding millennia -- including, probably, during the reign of Khafre.  In particular, the rump or rear of the Sphinx was carved out much later than the core body, and the head of the Sphinx has been recarved.

My geological work suggests that Khafre merely restored the Sphinx. The body of the Sphinx, carved from the local bedrock and thus sitting in the bottom of an artificial hollow (ditch), and the walls of the Sphinx enclosure exhibit well-developed precipitation-induced (p-i) weathering (characterized by a rolling and undulating vertical profile) not typically seen on Old Kingdom Giza Plateau structures (which exhibit primarily wind-induced weathering marked by a more angular profile with soft layers removed by wind abrasion) also excavated from the Mokattam limestone.  This deep p-i weathering of the Sphinx is interpreted as predating the current arid regime of the area, and thus indicates that the body of the Sphinx predates Old Kingdom times by perhaps several millennia.  Though we continue to refine our knowledge of the details of the paleoclimatic history of the Giza Plateau over the last 10,000 years, we already know enough to associate certain dominant modes of weathering with certain parts of that climatic history. Portions of the Sphinx predate Old Kingdom times. The temples adjacent to the Sphinx are built of limestone coreblocks taken from the ditch quarried out to form the body of the Sphinx.  These coreblocks are faced with Aswan granite attributed to Khafre, but the coreblocks were already deeply weathered when the granite facing was originally applied.  The first of several ancient repair campaigns to the weathered body of the Sphinx was done with typical Old Kingdom style masonry, but the core body of the Sphinx was already deeply weathered when this earliest repair work was carried out (see Robert M. Schoch, 1992, KMT, A Modern Journal of Ancient Egypt, vol. 3, no. 2, pp. 52-59, 66-70; Robert M. Schoch with Robert Aquinas McNally, 1999, VOICES OF THE ROCKS, New York: Harmony Books).  Corroborative evidence includes low-energy seismic refraction data that records up to 100\% deeper weathering below the original floor of the Sphinx enclosure as compared to weathering seen in the identical limestones in an area presumably quarried during Khafre's time in the rear of the Sphinx enclosure. Seismic investigations have also uncovered a series of cavities or chambers under the Sphinx (see Thomas Dobecki and Robert M. Schoch, 1992, Geoarchaeology, vol. 7, no. 6, pp. 527-544).