Robert Schoch, Boston University, Boston, USA 

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 o f a number of lines of geological, seismological, Egyptological,
and related evidence, I have come to the conclusion that the structure
commonly known as th e 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, th e rump or rear of
the Sphinx was carved out much later than the core body, and th e 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-d eveloped 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 a s 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 w e 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 associat e certain dominant modes of weathering
with certain parts of that climatic histor y.  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 whe n 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: Harmon y 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).


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