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This article was written in 1999-2000 and published in slightly modified form

 in 2002/2003, In Emilio Spedicato and Adalberto Notarpietro, editors, New Scenarios

 on the Evolution of the Solar System and Consequences on History of Earth and Man,

Proceedings of the Conference, Milano and Bergamo, June 7-9th, 1999,

 Universitŕ degli Studi di Bergamo, Quaderni del Dipartmento di Matematica,

Statistica, Informatica ed Applicazion,

Serie Miscellanea, Anno 2002, N. 3, pp. 171-203.


by Dr. Robert M. Schoch © 1999-2000




     Many recent Egyptologists have attributed the carving of the Great Sphinx of Giza to the Old Kingdom Pharaoh Khafre (Chephren), ca. 2500 B.C. However, 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 or recarved 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 or enclosure), and the walls of the Sphinx enclosure exhibit welldeveloped precipitationinduced (rainfall runoff) weathering, erosion, and degradation (characterized by a rolling and undulating vertical profile) not typically seen on Old Kingdom Giza Plateau structures (which exhibit primarily windinduced weathering marked by a more angular profile with soft layers removed by wind abrasion) also excavated from the Mokattam limestone. This deep precipitationinduced 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 so-called Sphinx Temple, located just east of the Great Sphinx, is built of limestone coreblocks taken from the ditch quarried out to form the body of the Sphinx. These coreblocks were faced with Aswan granite attributed to Khafre, but the coreblocks were already deeply weathered when the granite facing was originally applied. The same scenario may be true for the so-called Valley Temple just south of the Sphinx Temple. 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. Corroborative evidence for an older Sphinx 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.




        The Great Sphinx, carved out of limestones of the Eocene Mokattam Formation, standing 66 feet (20 meters) high and 240 feet (73 meters) long, sits on the edge of the Giza Plateau (just west of Cairo, Egypt) east of the three great pyramids. Most recent Egyptologists have attributed the carving of the Great Sphinx to the time of the Old Kingdom Fourth Dynasty Pharaoh Khafre (Chephren), approximately 2500 B.C. by various standard chronologies. In addition the so-called Sphinx Temple (sitting directly in front of the Great Sphinx) and Valley Temple (on the Sphinx's right side) are also attributed to Khafre (Lehner, 1992b, 1997).


        For many years the independent Egyptologist John Anthony West (see West, 1979, 1987, 1989, 1993a), based on the work of the late R. A. Schwaller de Lubicz (see Schwaller, 1982), has promulgated an interesting hypothesis: that the Great Sphinx of Giza may be older than its traditional attribution. Primarily on the basis of weathering and erosional features seen on the Great Sphinx and its associated temples, as compared to weathering seen on other structures attributed to the Fourth Dynasty, West suggested that the Sphinx may predate the Fourth Dynasty. West contacted me concerning his hypothesis in 1989, and although I was extremely skeptical of his ideas I did agree to look into it from a geological perspective. Beginning during the summer of 1990 West and I began to research this problem in earnest, including several expeditions to Egypt specifically to look at the evidence bearing on the age of the Great Sphinx (see Schoch, 1992a, 1992b, 1992c, 1992d, 1992e, 1993a, 1993b, 1994a, 1994b, 1995a, 1995b, 2000; Schoch with McNally, 1999, 2000; Schoch and West, 1991; West, 1993a, 1993b; see also Moore, 1992, and Payn, 1992).





        Major geological and field evidence bearing on the age of the Great Sphinx is summarized in this section. I have divided this evidence into four main categories:


1) Weathering Patterns, 2) Two-Stage Construction of the Sphinx and Valley Temples, 3) Ancient Repair Campaigns to the Body of the Sphinx, and 4) Seismic Surveys of the Sphinx Area.


Weathering Patterns


        Modifications to rock surfaces, such as those resulting from weathering, erosion, and paleosol development, have long been utilized as criteria in determining the relative times since fresh rock surfaces were first exposed to the elements (see, for example, Brookes, 1985; Coates, 1984; Evans, 1985; Finkl, 1984; and Vreeken, 1984). Such methodologies have been widely used to date Quaternary land surfaces in particular, but the same concepts can also be applied to other dating problems -- such as the age of the initial carving of the Sphinx relative to other cultural features found on the Giza Plateau.


There appear to be four distinct forms or modes of weathering and erosion

(degradation) exhibited on the Giza Plateau.


1) Precipitation-induced weathering and erosion is seen on the body of the Sphinx and in the ditch or hollow surrounding the Great Sphinx. This gives a rolling and undulating vertical profile to the weathered rocks, and is very well-developed and prominent within the Sphinx enclosure. The rocks that display this mode of weathering also often contain prominent vertical crevices and other solution features, as well as cross-cutting diffusion fronts (see El Aref and Refai, 1987 [discussed further below], who thoroughly describe these features; see also Issawi, 1992, p. 17, who notes that "in parts of the statue [the Sphinx], the limestone is highly porous and cavernous showing evidences of being greatly affected by water erosion."). Many of the vertical and inclined solution features follow joints and faults in the bedrock.


2) Wind-induced weathering and erosional features are seen on structures that are attributed unambiguously to Old Kingdom times. In this mode of weathering the original profiles of the carved faces of tombs and other structures are still clearly visible (sometimes containing easily legible hieroglyphic inscriptions) but the softer, less competent layers of rock have been "picked out" by wind and sand abrasion with the consequent formation of deeply eroded "wind-tunnel" features that give a relatively angular profile to the vertical rock surface. This wind-induced weathering is distinctly different in nature from the precipitation-induced weathering; it is well exemplified on various Old Kingdom tombs (such as on the tomb of Debhem, a late Old Kingdom overseer [illustrated in Schoch, 1992d, p. 57]) and structures south and west of the Sphinx which have been carved from the same sequence of limestones as the body of the Sphinx. Wind-induced weathering is also observed on the present head of the Great Sphinx and to a certain degree on the uppermost portion of the back of the Sphinx as well as on the uppermost limestone blocks of the Valley and Sphinx Temples. Wind-induced weathering features in the Sphinx enclosure form a relatively minor overlay on the precipitation-induced weathering features observed on the body of the Sphinx and on the walls of the enclosure. This wind-induced weathering may be due in part to the hot, dry, dust-laden khamsin winds that seasonally (March to mid-June) originate from the interior of the Sahara Desert and blow over the country.


3) Present on the body of the Sphinx, as well as on other structures (and essentially forming an overlay on many precipitation-induced and wind-induced megascopic weathering features), are weathering features that are interpreted as the result of relatively recent (within the last couple of centuries) efflorescing of dissolved and recrystallized minerals (such as halite) on the surface of the rock which have subsequently flaked off and deteriorated the stone. It has been suggested that subsurface moisture migrating up into the Sphinx and the surrounding rocks may account for much of this activity (see Gauri and Holdren, 1981). Alternatively, or complementarily to the migration of subsurface groundwater, similar weathering is actively taking place during the present day due to the condensation of atmospheric moisture on the rock. As described by Gauri, Chowdhury, Kulshreshtha, and Punuru (1988, pp. 725-726), "the moisture is able to condense as droplets of water in the cool of the night. This moisture forms concentrated salt solution, a process augmented by the hygroscopicity of the existing halite. The salt solution enters the pores under the influence of capillary force. At sunrise, as the water begins to evaporate, crystals of salt grow producing crystallization pressure. Often one can hear in the morning the sound of popping stone resulting from pressures produced under the surface layers."


        Gauri, Holdren, and Vaughan (1986) have suggested that much of the deterioration of the Sphinx is due to the migration of salts under the influence of water originating from the atmosphere. These authors (Gauri et al., 1986, pp. 4-5) state: "Burial of the Sphinx for centuries under the desert sand has, it appears, resulted in the migration of salts from the depth of the bedrock toward the surface. The authors deduced this phenomenon from observations made in the process of mapping the Sphinx geologically [Gauri, 1984], when sand was removed that had piled up in recent times against the rock surfaces bounding the ditch around the Sphinx. Even though the sand appeared dry at the surface, it was completely soaked with water a few inches below the surface. Also, the bedrock in contact with the sand was soaked with water. The source of this water is the atmosphere, and not the subsurface, because the water table lies many meters below the surfaces under consideration. Therefore, during the long burial of the Sphinx, the rock must have become wet to a considerable depth, and as it dried when exposed to the sun, the salts must have become concentrated in the surface layers."


        As is pointed out later in this paper (see section on "Ancient Repair Campaigns to the Body of the Sphinx"), the vast majority of the weathering and erosion occurred to the Sphinx prior to circa 1400 B.C. In places the walls of the Sphinx enclosure exhibit over a meter (3.3 feet) of erosion, and in places perhaps over two meters (6.5 feet) of erosion (see, for instance, the profile in Gauri, 1984, p. 32). It is hard to imagine that the mechanism of migrating salts, described in the last paragraph (quoted from Gauri et al., 1986), could be solely responsible for producing these deep weathering features in the time span from 2500 B.C. (when Khafre presumably had the Sphinx carved) to 1400 B.C. It is particularly difficult to reconcile Gauri et al.'s (1986) proposed weathering mechanism with the observed surficial morphology of the rocks in consideration of the following points: 1) As is described below, the Sphinx enclosure may have been buried in sand for at least half of the period between 2500 B.C. and 1400 B.C.; 2) the weathering patterns seen on the body of the Sphinx and the walls of the Sphinx enclosure clearly exhibit features associated with precipitation-induced weathering (cf. El Aref and Refai, 1987); and 3) as has already been pointed out, Old Kingdom tombs and other structures on the Giza Plateau that were carved from the same member of the Mokattam Formation do not exhibit the same weathering features to the degree seen on the body of the Sphinx and the walls of the Sphinx enclosure. If Gauri et al.'s (1986) mechanism of migrating salts since 2500 B.C. was the primary agent responsible for the weathering and erosional features seen on the body of the Sphinx and on the walls of the Sphinx enclosure, then one should expect to observe weathering and erosional features of a similar nature and degree on the Old Kingdom tombs and other structures that are carved out of the same sequence of limestones as the body of the Sphinx.


4) Weathering due to the dissolution and recrystallization of calcite and other minerals in the rocks is visible within various tombs and chambers cut into the bedrock of the Giza Plateau. This may occur on a daily basis as water condenses on the cool surfaces of these man-made caves, and subsequently evaporates once again as the temperature rises; this gives the surface of the rock, and any carvings it may bear, almost the appearance of slightly melted wax, at times covered with a very fine coat of mineral crystals. This is the most minor component of weathering observed on the Giza Plateau. It is preserved in only a limited number of tombs and other artificial cave-like structures, such as tombs directly north of the Sphinx on the eastern edge of the Giza Plateau.


        Of the four modes of weathering listed above, some rocks may show one mode of weathering overlain by another -- thus in particular cases the various modes of weathering may be somewhat difficult to sort out. On the whole, however, they are clear and distinct from one another on the Giza Plateau.


        What is interpreted as precipitation-induced weathering and erosion (#1, above) is the oldest predominant mode of weathering identified on the Giza Plateau. It is found only on the oldest structures of the Giza Plateau to any significant degree, such as the body of the Sphinx and the walls of the Sphinx enclosure. Of course it still rains on the Giza Plateau occasionally, and thus precipitation-induced weathering can be said to be found on all Giza Plateau structures to some small degree; here we are talking in generalities and attempting to look at the broad picture. In many places this precipitation-induced mode of weathering has superimposed upon it wind-induced weathering (#2, above). Presumably the major portion of this precipitation-induced weathering occurred prior to the onset of the current arid regime exhibited on the Giza Plateau (i.e., prior to the modern climatic regime of the Sahara Desert). On the Saqqara Plateau (about 10 miles [16 km] from Giza) there are fragile mudbrick mastabas that are indisputably dated to the first and second dynasties (presumably several hundred years earlier than the standard dating of the Sphinx) that exhibit no evidence of the precipitation-induced weathering seen in the Sphinx enclosure. Indeed, the mudbrick mastabas on the Saqqara Plateau have been preserved by being buried in dry, wind-swept sand, indicating that extremely arid conditions have persisted in this part of Egypt since early Old Kingdom times. As noted above, well-documented Old Kingdom tombs on the Giza Plateau, cut from the identical sequence of limestones as the body of the Sphinx, exhibit well-developed wind-induced weathering features but lack significant precipitation-induced weathering features. For these reasons it can be concluded that the well-developed precipitation-induced weathering features seen on the Great Sphinx and associated structures predate Old Kingdom times, and in fact may well predate dynastic times.


        The other two modes of weathering noted above (#3, efflorescing of dissolved and recrystallized minerals, and #4, dissolution and recrystallization of calcite) appear to be, on the whole, phenomena that have been significant only recently. In the 1960s the Aswan High Dam was built, and this, along with the accompanying intense agriculture and the generally burgeoning population of Egypt, has served to raise water table levels generally throughout the lands along the Nile. The annual floods of the Nile are now largely controlled artificially, and the water level of the Nile no longer is allowed to rise and fall as it did in earlier times. This means that salts which were once flushed from the rocks on a regular basis now accumulate and deteriorate stone monuments and buildings. Hillel (1991, pp. 148-149) describes the current situation in Egypt as follows:


        Intensified irrigation and the maintenance of the water level in the Nile have afflicted Egypt with still another salinity problem beyond its irrigated lands. Instead of being flushed out, as they were in the past, by receding flood waters, the salts that now remain in the groundwater are infused by capillary action into the porous soil and rocks. Water piped in to supply the needs of the expanding population of towns and villages along the Nile, and cesspools placed underground to dispose of their waters, have further raised the water table. As a result, there is now a constant upward seepage of salt-bearing moisture into Egypt's ancient temples and monuments, and these salts impregnate the porous stone walls.


        As they say in Egypt, 'salt is like a sleeping devil--only when it gets moist does it start to act.' When the moisture evaporates at the exposed surfaces of these structures, the salts recrystallize, forcing apart the grains of stone. The result is a flaking and crumbling of the ornately carved reliefs and inscriptions of Egypt's magnificent monuments. Salt bubbling up under the ancient wall paintings pushes the plaster off the walls, so that the exquisitely drawn and brightly colored portraits of the ancient kings, queens, and gods, as well as the vivid depictions of landscapes and scenes of daily life (notably including farming activities), are now deteriorating rapidly. If this deterioration continues for a few more decades, many and perhaps most of the reliefs and paintings adorning the ancient temples and graves will be erased from within, and only blank, pulverized surfaces of walls and columns will be left."


        All of these detrimental effects of rising water tables are currently exhibited on the body of the Sphinx, and around the area of the Giza Plateau generally. Other researchers have focused attention on these modes of weathering relative to the Sphinx, particularly the damage currently being done by mobilized salts (see for instance the work by Gauri and Holdren, 1981; Chowdhury et al., 1990; Punuru et al., 1990; Gauri and Punuru, 1989; Gauri et al, 1986; Gauri et al., 1988; Gauri, 1992; see also the article by Brock, 1990). These studies are of extreme importance in attempting to halt the current destruction of the Sphinx (Brookes, 1992; Egyptian Antiquities Organization, 1992; Hedges, 1992). It must be remembered, however, that studies of the weathering agents currently damaging the Great Sphinx may not be of relevance when attempting to determine the genesis of ancient weathering and erosional features on the Sphinx.


        In their work on the weathering of the Sphinx Gauri and his colleagues (see references cited above) have suggested that in general the upper beds of the middle member (Member II or Setepet Member) of the core body or thoracic region of the Sphinx are more durable than the lower beds of this member. These workers have calculated durability factors for different beds of this member; such factors range from about 100 (high durability) for the uppermost bed just below the neck of the Sphinx to about 11 for the lowermost bed of the member. There is a general trend of increasing durability factors, as calculated by these authors, going up section. Thus their bed 4i (located approximately halfway up the body of the Sphinx) has a calculated durability factor of 75 (see summary of this work in Gauri et al., 1988).


        It is significant to note that on the wall of the Sphinx ditch the beds for which Gauri et al. calculate the highest durability factors are not consistently the least weathered and receded in profile (assuming that the wall of the Sphinx ditch was originally cut vertically or nearly vertically, perhaps at an angle of 80 degrees or so). For instance, utilizing Gauri's own data (Gauri, 1984, p. 32, fig. 3C), in an east-west profile of the rear of the Sphinx and the wall of the Sphinx ditch one sees that beds 1i and 2i, which both have low durability factors of 11, are greatly receded and undercut the overlying units of higher durability (beds 1ii and 2ii). However, in the same section bed 2ii (with a durability factor of 76) is receded further back than is the lower-lying bed 1ii (durability factor of 56). Likewise, bed 3ii (durability factor of 76) is receded further back than the underlying bed 3i (durability factor of 42), and beds 4i and 4ii (durability factors of 75 and 86 respectively) are receded further back than the lower-lying bed 3ii. In general, the amount that a bed has receded is not so much a function of its present-day durability factor, but primarily a function of its geometric position on the exposure. It would be logical that precipitation falling down from above would preferentially weather the uppermost beds and cause them to recede back at a faster rate than the lower beds. Again, this train of thought suggests that the Sphinx and walls of the Sphinx ditch were subjected to precipitation-induced weathering.


        There have been a few other previous studies of note concerning weathering and erosion on the Giza Plateau. Emery (1960) and Said and Martin (1964) discussed briefly the weathering to the pyramids, but their work is not directly applicable to the present discussion. More pertinent to the topic at hand, El Aref and Refai (1987) made a comprehensive macroscopic study of paleokarst processes and features on the Giza Plateau, concentrating in particular on the area of the Sphinx enclosure. These authors pointed out many paleokarst features that are attributable to periods of seasonal rainfall. They illustrate and discuss solution holes, solution depressions, solution joints, symmetrical concentric cross-cutting diffusion fronts, and other dissolution features found on the body of the Sphinx and on the walls of the Sphinx ditch. El Aref and Refai (1987, p. 376) note that "The karstic rocks are mantled by soil material and/or surficial calcareous duricrust. The solution features are partially or completely filled with clay precipitates together with concretions of iron and manganese oxides and collapse breccia fragments." (As a side note, these iron and manganese oxides often take on a red or ocher color. Lehner [1991, p. 36] noted that "if you probe any seam in the masonry covering the lower part of the body [of the Sphinx], a red powder appears." This may simply be red earthy/clay material, typical karst sediments that one would expect in such a limestone terrane that has been subjected to weathering via precipitation. Lehner [1991] and Hassan [1949] both suggest that the Sphinx and surroundings were traditionally painted red. This putative red paint, however, may actually consist, in part, of natural weathering products of the rock, although the Sphinx may have been artificially painted red also.) El Aref and Refai conclude (1987, p. 376) that "The development of these karst features and the associated sediments indicate that the study area was subjected to intensive seasonal rainfall and evaporation of temperate (Mediterranean) climatic conditions."


        If the Great Sphinx was weathered heavily, and at an early period, by precipitation, this suggests that it may have been carved prior to the last period of major precipitation in this part of Egypt. Egypt was subjected to erratic floods and what is sometimes referred to as the "Nabtian Pluvial" (a period of relatively heavy rainfall) from 12,000 or 10,000 to about 5,000 years ago, and it has been suggested that there were sporadic but relatively heavy rains during the fourth millennium (4,000 to 3,000) B.C., and a less arid climate along the Nile as late as the middle of the third millennium B.C. (with relatively wetter conditions and unusually high Nile floods recorded sporadically during historical times; for a recent summary of the evidence bearing on the Holocene climatic history of northern Egypt see Said, 1990; see also Bower and Lubell, 1988, Clark and Brandt, 1984, Close, 1987, Holmes, 1989, and references cited therein).


        Hayes (1965, p. 23) summarized much of the classical work carried out on reconstructing the climate of this period in Egypt's history when he wrote: "Toward the end of the sixth millennium B.C. Egypt and neighboring lands appear to have enjoyed another slight, but effective increase in temperature and precipitation and to have entered upon a prolonged sub-pluvial or relatively moist phase, extending from early Neolithic times until late in the Old Kingdom (ca. 5000-2350 B.C.). . . . Since the end of the third millennium B.C. the climate of Egypt has been generally similar to that of the present day. Between 2350 B.C. and A.D. 700 the average temperature seems to have been, if anything, a trifle above and the average rainfall a little below the modern levels, but with at least two 'quite moist' spells, one in late Ramesside times [circa 1200-1100 B.C.] and one about 850 B.C." Butzer (1971, p. 584) summarized his well-known work on the same topic as such: "The Nile Valley provides further details and confirmation of several moist intervals . .  A period of accelerated wadi activity that began 9200 B.C. terminated by 6000 B.C. Shell proliferations suggest rather more vegetation in the wadis. A little later, ca. 5000 B.C., a red paleosol suggests a mat of vegetation and more frequent gentle rains. Finally, after a second dry interlude, accelerated wadi activity and extensive sheet washing in the wake of sporadic but heavy and protracted rainsare indicated ca. 4000-3000 B.C. Historical and archeological documents suggest that the desert wadi vegetation of northern and eastern Egypt was more abundant as late as 2350 B.C., when the prevailing aridity was established." Needler (1984, p. 17) summarized the relevant climatic history as follows: "In the late sixth millennium B.C. a slightly less arid climate set in, following a brief hyperarid episode abound 6000 B.C. These somewhat more favorable conditions lasted, with the exception of short hyperarid interruptions, until about 2400 B.C. During the first part of this period, the 'Neolithic Wet Phase,' some Epi-Palaeolithic hunters and collectors must have coexisted with new and expanding agricultural communities [in Egypt]."


        On the basis of the climatic history outlined above, one might tentatively suggest that the Great Sphinx was built in very early dynastic times or late predynastic times (late fourth millennium or earliest third millennium B.C.). However, one must account for the considerable weathering that appears on the walls of the Sphinx hollow, on the body of the Great Sphinx itself, and on the walls of the Valley and Sphinx Temples (see below) -- in the case of the Great Sphinx and its associated temples, weathering that was possibly covered up or repaired during the Old Kingdom (circa 2600-2400 B.C.). One must also take the seismic data into account (see below). These latter considerations suggest the possibility that the initial carving of the Great Sphinx may be at least several millennia older than its standard attribution.


Two-Stage Construction of the Sphinx and Valley Temples


        As far as can be determined, the core of the Sphinx Temple (and possibly the core of the Valley Temple) is constructed out of titanic limestone blocks taken directly from the ditch around the Sphinx (see the work of Aigner, 1982, 1983a, 1983b, 1983c, and Lehner, 1980, 1985a, 1985b, 1991, 1992a, 1992b, 1997). Therefore the limestone core of the Sphinx Temple (and also probably the Valley Temple) must be as old as the Great Sphinx itself. The limestone cores of these temples were later (perhaps thousands of years later; see discussion that follows) faced by the ancient Egyptians with ashlars (casing stones) made of Aswan granite (see Lehner, 1992b, who notes that the limestone cores of both temples were cased in granite at some point in their history). It also appears that the limestone cores of the temples, especially that of the Valley Temple, were perhaps partially rebuilt by the dynastic Egyptians. Based on my field observations, I believe that certain limestone blocks, as well as a few granite blocks, in the Valley Temple specifically do not originate from the Sphinx enclosure. These blocks are probably not original to the temple, but constitute additional blocks that were introduced during dynastic rebuilding of the temple. Since Old Kingdom times virtually all of the granite has been removed from the Sphinx Temple and much of the exterior granite has disappeared from the Valley Temple; this robbery of the granite may have taken place primarily during New Kingdom times (circa 1400-1100 B.C.; Lehner, 1992b) and later.


        Based on my field observations of the granite ashlars and the underlying limestone blocks, I believe that the limestone core blocks of both the Sphinx Temple and the Valley Temple were exposed to the elements and underwent considerable weathering and erosion before the granite was put into place. In places the backs of the granite facing blocks were cut in an irregular, undulating pattern so that they would complement or match the irregular weathering pattern on the limestone blocks that they were used to refurbish. In observing the Valley Temple in particular, one also notes that the limestone walls, where stripped of their granite, are not cut smoothly. Rather they have a higgledy-piggledy surface pattern where apparently the ancient Egyptians, before resurfacing the temple with Aswan granite, slightly cut back and smoothed out the weathered surface of the wall, but they did not take off enough weathered surface to make the wall perfectly smooth. Perhaps the ancient Egyptians, in renewing the temples with granite, were also consciously preserving as much of the original limestone structures as possible. Conceivably the original limestone structures were, even then, considered to be very ancient and very sacred.


        The general Egyptological community agrees that the granite facing on the Sphinx  and  Valley Temples is attributable to Khafre (see, for instance, Hawass, 1990, 1998). On site I found an inscription carved into the granite of the Valley Temple

which according to West (personal communication; see also Edwards, 1985; Grinsell,

 1947; Hawass, 1990) appears, on stylistic grounds, to be an Old Kingdom inscription.


        It seems a good assumption that the limestone core blocks would have been freshly cut (that is, unweathered) when initially used to construct the temples. Therefore if the granite facing is covering deeply weathered limestone, the original limestone structures must predate by a considerable degree the granite facing. Obviously, if the limestone cores (originating from the Sphinx ditch) of the temples predate the granite ashlars (granite facings), and the granite ashlars are attributable to Khafre of the Fourth Dynasty, then the Great Sphinx was built prior to the reign of Khafre. Note, however, that the attribution of the granite ashlars to the time of Khafre is itself circumstantial. As mentioned above, the ashlars bear Old Kingdom inscriptions and therefore must be at least as old as the Old Kingdom. But the Old Kingdom inscriptions could conceivably have been carved into still earlier structures.


Ancient Repair Campaigns to the Body of the Sphinx


        The body of the Sphinx has been subjected to various repair campaigns, beginning with the ancient Egyptians themselves and continuing up to the present day. The earliest repairs to the body of the Sphinx have been carried out using what appear to be Old Kingdom style masonry techniques. Gauri and his colleagues (see for instance Punuru et al., 1990, p. 230) consistently refer to these in such terms as "Pharaonic veneer stones" that have experienced "5,000 yr of exposure to local conditions," that is, they were applied during Old Kingdom times. Likewise, Hawass (1992, p. 14) states that: "It seems that the Sphinx underwent restoration during the Old Kingdom because the analysis of samples found on the right rear leg proved to be of Old Kingdom date." If the oldest repairs to the eroded body of the Sphinx do date to Old Kingdom times, this is another strong argument in favor of a much earlier date for the Sphinx.


        Lehner has analyzed the repair campaigns to the Sphinx (see Lehner, 1980; Hamblin, 1986), concluding that, despite his own evidence to the contrary, "To seek agreement with known historical facts [i.e., his contention, among other things, that the Sphinx was built in circa 2500 B.C. by Khafre], we should probably expect the earliest restoration to have been done in the New Kingdom [circa 1500-1400 B.C.]" (Lehner, 1980, p. 18). In summary, in order to save the attribution of the Sphinx to Khafre (Chephren), circa 2500 B.C., Lehner suggests that the earliest level of "large-block" (Old Kingdom style?) masonry was added to the Sphinx during the New Kingdom. Taking not only Lehner's work into account, but also the evidence for the two-stage construction of the Sphinx and Valley Temples (discussed above), the research that has been carried out concerning different modes of weathering on the Giza Plateau (discussed above), and the seismic surveys in the area of the Sphinx which give data on the subsurface depth and distribution of weathering around the Sphinx (discussed below), and considering the fact that the attribution of the Sphinx to Khafre is based on circumstantial evidence to begin with (see Schoch with McNally, 1999, 2000), I find one conclusion inescapable -- the initial construction (carving) of the core body of the Sphinx predated the time of Khafre. Lehner's own work is more easily reconciled with the hypothesis that the Fourth Dynasty Egyptians merely restored, refurbished, and added to the Sphinx and its associated structures, rather than being the original creators of the Sphinx complex.


Seismic Surveys of the Sphinx Area


        Seismic geophysical surveys (Dobecki, 1992; Dobecki and Schoch, 1992) indicate that the subsurface weathering in the Sphinx enclosure is not uniform. This strongly suggests that the entire Sphinx ditch was not excavated at one time. Furthermore, by estimating when the less weathered portion of the Sphinx enclosure was excavated and thus first exposed subaerially one can tentatively estimate when initial excavation of the Sphinx enclosure may have begun.


        During our April 1991 trip to Egypt, Dr. Thomas L. Dobecki, a seismologist then with McBride-Ratcliff and Associates of Houston, Texas, helped us carry out some low-level seismic work in the vicinity of the Great Sphinx with the permission of the Egyptian Antiquities Organization. We were able to gather a quantity of seismic data, and with this data we have been able to establish subsurface geometries of the bedrock and have located several previously unknown features below the surface.


        Nineteen refraction profiles, two reflection profiles, and a refraction tomography data set were collected on the Giza Plateau during April 1991. The seismic work performed around the base of the Sphinx consisted of hitting a sledgehammer on a steel plate, thus generating energy waves that entered the rock, travelled into the subsurface, and reflected and refracted off of subsurface features. In the Sphinx enclosure refraction profiles gave us information on the subsurface weathering of the rock. In addition, we located various voids, cavities, and other subsurface features (see Dobecki and Schoch, 1992).


        Analysis of the seismic data collected in April of 1991 contributes further to exploring the age of the Great Sphinx. Seismic lines taken in front of and along the body of the Great Sphinx on either side (east [seismic line S4], north [seismic line S1], and south [seismic line S2] of the Sphinx) indicate that below the surface the limestone is weathered up to six to eight feet [1.8 to 2.5 meters] deep. However, along the back (west side [seismic line S3]) of the Great Sphinx the identical limestone has only been weathered to a depth of approximately four feet [1.2 m]. These results were completely unexpected. It is the same limestone that surrounds the Great Sphinx (the floor of the Sphinx enclosure where all of the seismic lines were taken consists of Gauri's [1984] Rosetau Member, or Member I), and if the entire body of the Great Sphinx was carved out of living rock at one time, it would be expected that the limestone surrounding it should show the same depth of subsurface weathering. One possible interpretation of the data we collected is that initially only the sides and front (eastern portion) of the body of the Great Sphinx were carved free from the rock, thus projecting from the rock outcropping, while what would later become the back or rump (western end) of the Sphinx originally merged with the natural rock. To be more precise, the rump was probably initially carved down only to the level of the upper terrace (about 11.5 feet [3.5 meters] above the present floor of the Sphinx enclosure at the rump), which to this day remains immediately west of the Sphinx within the general Sphinx enclosure; below the level of the terrace the back of the Sphinx merged with the bedrock. Hassan (1949) suggests that the Sphinx was originally meant to be viewed from the front (rather than from the sides or rear), such that, with the Sphinx Temple before it, the Sphinx seems to sit on a pedestal. Alternatively, the rump or western end of the Sphinx may have been originally freed from the rock, but separated from the bedrock by only a very narrow passage not sampled by our April 1991 seismic line. In order to determine accurately when the western end of the Great Sphinx was freed from the bedrock, and to establish a chronology of the possible widening of the passage between the western end of the Sphinx and the bedrock, more detailed work (including the collection of several more seismic profiles parallel to seismic line S3) will be necessary. However, it is already clear that the limestone floor behind the rump (western end) of the Sphinx which we sampled seismically in April 1991 was exposed later (i.e., probably in Khafre's time) than the east, north, and south limestone floors. Once the sides of the body and eastern end of the Sphinx were carved, the limestone floor surrounding it began to weather, but what was to become the limestone floor behind the western end of the Sphinx was still protected by a thick layer of solid rock.


        A reasonable hypothesis is that when Khafre (circa 2500 B.C.) repaired and refurbished the Great Sphinx, the Sphinx Temple, and the Valley Temple, he either had the back (western end) of the Great Sphinx carved out and freed from the cliff or widened an existing passage behind the western end. It is difficult to argue that the back (rump) of the Sphinx was carved out and freed any later than Khafre's time; the rump has, like the rest of the core body of the Sphinx, been weathered and repaired with limestone blocks of various ages, including blocks that date back to at least New Kingdom times (see various articles by Lehner and discussion above) so the rump must have been freed well before New Kingdom times in order to have required repairs during the New Kingdom. Furthermore, one must account for the non-trivial four feet (1.2 meters) of subsurface weathering detected behind the rump of the Sphinx. It seems unlikely that this amount of weathering could have occurred since New Kingdom times.


        As an alternative to the scenario that Khafre had the back of the Sphinx carved free from the bedrock, one could suggest that if the back of the Sphinx was already freed from the bedrock prior to Khafre's time, but only separated from the cliff by a very narrow passage, Khafre may have widened this passage and uncovered the limestone floor that we sampled seismically. Our seismic line was positioned very close to the western wall of the Sphinx ditch. The Sphinx Temple also sits in a hollow carved out of bedrock just east of the Sphinx. Along the outside of the northern wall of the Sphinx Temple it appears that the bedrock face of the adjacent wall was cut-back so as to widen the passage between the temple wall and the carved limestone bedrock wall to the north, thus making room for the refurbishing of the wall with newer granite blocks. Possibly both of these areas, behind the rump of the Sphinx and north of the Sphinx Temple, were widened at the same time -- presumably around the time of Khafre.


        Once exposed, the limestone floor on the western end of the Sphinx began to weather. Assuming that the floor of the western end was first carved out around the time of Khafre, and given that there is 50% to 100% deeper weathering of the limestone floor on the sides and front of the Sphinx as compared to the floor in back of the Sphinx, we can estimate that the initial carving of the Great Sphinx (i.e., the carving of the main portion of the body and the front) may have been carried out circa 7,000 to 5,000 B.C. (that is the initial carving of the core body of the Sphinx is approximately 50% to 100% older than 2500 B.C.). It can be argued that this tentative estimate is a minimum date; given that weathering rates may proceed non-linearly (the deeper the weathering is, the slower it may progress due to the fact that it is "protected" by the overlying material), the possibility remains open that the initial carving of the Great Sphinx may be even earlier than 9,000 years ago (see further discussion below).


        Admittedly, estimating the date of the initial carving of the Great Sphinx by discrepancies in the depth of subsurface weathering below the floor of the Sphinx enclosure is less accurate and precise than we might desire. However, in the absence of other data and tests (such as proposed measurements of cosmogenically-produced isotopes in the surface layer of the rock of the Sphinx), we must work with the evidence at hand. I have pondered long and hard the many complex factors that could enter into the rate of subsurface weathering around the base of the Sphinx. Weathering rates may vary over time. As the climate was generally moister at an earlier period (prior to the middle of the third millennium B.C.) this might suggest that weathering progressed faster and deeper at this earlier period around the north, east, and south sides of the Sphinx (before the western end was freed from the bedrock). However, the subsurface weathering seen around the base of the Sphinx would not necessarily be accelerated by a moister climate per se.


        The subsurface weathering is probably primarily a function of alternating periods of moisture collecting on the surface of, and penetrating within, the rock followed by evaporation -- this cycle might take place on a daily, seasonal, or longer time-scale. The effects of a rainy versus more arid climate may be fairly minimal in terms of this particular weathering phenomenon if the alternating cycle of moisture penetration and evaporation occurred on a regular basis (as it seems to at the present time within the Sphinx enclosure) under various climatic regimes. If the limestone floor of the Sphinx enclosure were completely covered with standing water that did not evaporate off, the standing water might serve more to protect the limestone than weather it (after all, the limestone was originally precipitated in water). In other words, the absolute frequency of the number of rain/evaporation cycles may be more important relative to the subsurface weathering than the absolute volume of rainfall. The Giza Plateau has had a mean annual rainfall of about one inch (2.5 cm) per year since Old Kingdom times. During the earlier temperate wet period (the time of pluvials) the frequency of rainfall was undoubtedly greater, but any collected water may not have evaporated as quickly and completely. Also, as noted already, depth of weathering does not typically proceed linearly if, as in the case of the floor of the Sphinx enclosure, the overlying weathering products (the weathered rock) are not removed. As weathering depth increases, the rate of weathering decreases due to the protection afforded by the overlying material. Thus even if we postulate that the base of the original Sphinx structure initially weathered a bit more quickly due to moister climatic conditions prior to five thousand years ago, this initially faster rate of weathering would quickly decelerate as weathering depth increased.


        Taking the various factors that could affect the rate of subsurface weathering around the base of the Sphinx into account, as a first approximation I have simply assumed that the factors that would tend to accelerate the rate and depth of weathering are canceled by the factors that would tend to slow the rate and depth of weathering. On this basis I have used a linear extrapolation to estimate that the initial carving of the core body of the Great Sphinx occurred during the period of approximately 7,000 to 5,000 B.C. I believe that the estimate of 7,000 to 5,000 B.C. for the initial carving of the Sphinx is crude, but consistent and compatible with all of the other evidence at hand.


        It should also be noted that we ran a north-south seismic line [line S9] through the Sphinx Temple east of the Great Sphinx (Dobecki and Schoch, 1992). This line also shows a weathered layer above a sound limestone layer, with a uniform depth of weathering of about four to five feet [1.2 to 1.5 meters]. Given the contention that the Sphinx Temple was constructed at the same time as the carving of the Great Sphinx, this depth of weathering under the floor of the Sphinx Temple may be considered abnormally shallow. However, there is evidence that the current surface of the floor of the Sphinx Temple is lower than the original surface. Pillars inside the Sphinx Temple stand on rock pedestals - - it seems evident that the floor was lowered around them. It appears probable that the original, weathered floor of the Sphinx Temple was lowered and resurfaced during Old Kingdom restorations and refurbishing to the Sphinx Temple.


        In addition to the unanticipated differential weathering around the body of the Great Sphinx, our seismic work also revealed several other interesting subsurface features. For example, there is clear evidence of a possible void or chamber under the left paw of the Sphinx (Dobecki and Schoch, 1992). The seismic profiles indicate that the Great Sphinx and Sphinx Temple sit on a steep cliff (now buried in sand [seismic line S10]), and beyond this cliff are several elusive downdrop structures in the bedrock surface; these features may be either natural or man-made. In all, nineteen seismic profiles (seventeen collecting refraction data, and two collecting both refraction and reflection data) were taken. The geophysical data collected during the April 1991 trip to Egypt is described in more detail in Dobecki and Schoch (1992).




Recently the authors Lawton and Ogilvie‑Herald have summarized the major arguments against an older Great Sphinx in their book GIZA: THE TRUTH (1999).  Here I will summarize and comment on some of the arguments they discuss.


        Lawton and OgilvieHerald (page 313) agree with me that the current arid climatic regime of the Giza Plateau began approximately in the middle of the third millennium B.C. (circa 2350 B.C. by one standard dating scheme) and there were various periods of relatively heavy rainfall from about 10,000 or 8,000 B.C. up until the onset of the predominant aridity that has existed in the area for the last 4500 years or so. Lawton and OgilvieHerald also correctly point out that there were occasional rains, even heavy rains, during dynastic Egyptian times and up through the present day, resulting in periodic flash floods. Still, as will be discussed further below, such flash floods actually have little bearing on the weathering, erosion, and ultimately the determination of the age of the oldest portion of the Sphinx (here it is important to remember that the Great Sphinx was refurbished and partially recarved, including a recarving of the head, in dynastic times - - originally it may not have even looked like a Sphinx; see Schoch with McNally, 1999, 2000; West, 1992).


        Sporadic heavy rains and the resulting flash floods (due to the inability of the rain to penetrate and soak into the land's surface and thus it runs off and collects in valleys, wadis, and other depressions) commonly found in arid regions do have tremendous potential to move loose debris and even cause serious erosion. However, in my opinion as a geologist, the nature and especially degree of weathering seen in the Sphinx enclosure and on the body of the Sphinx itself, is incompatible with sporadic flash floods since dynastic times. Even if occasional heavy rains occur on the Giza Plateau, the fact remains that currently on average only about an inch of rain each year occurs in the region (25 to 29 mm annually).


        I do not believe that there has been enough rainfall in the area over the last 5000 years to account for the tremendous degradation of the actual limestone bedrock as seen on the western end of the Sphinx enclosure, much less to account for the extreme weathering and erosion seen on the core body of the Sphinx itself. The latter is an important point, because in the case of the body of the Sphinx only the back (top) of the Sphinx serves as a catchment area for any subsequent runoff. From what we understand of the climate of the area, it strains credulity to suggest that this weathering and erosion is the result of rainfall during the last 4,500 years. This is even more so the case when we take into account the calculations of Lawton and OgilvieHerald (page 312) that the Sphinx enclosure and body of the Sphinx have been buried in sand, and thus effectively protected from this type of erosion, for 3,100 of the last 4,500 years.


        Furthermore, based on the perceptive analysis of the geologist Colin Reader (1998; discussed below), since at least the time of Khufu (circa 2550 B.C. according to one standard chronology), the Sphinx has not even been situated in a position where it could receive the brunt of such flash floods. Among ancient Egyptian structures, those that show clear signs of having been damaged or otherwise significantly affected by the occasional heavy rains and resulting flash floods are those situated in valleys, wadis, and other low areas that serve as channels for the collected water. Lawton and OgilvieHerald cite the Valley of the Kings at Luxor as a case in point, and other authors have cited Reisner's suggestions of flood damage to the Menkaure valley temple on the Giza Plateau. Potential flood damage to Menkaura's valley temple is very different in kind and degree than the actual erosion and degradation of limestone bedrock as seen in the Sphinx enclosure. According to Lehner (1997, p. 137), Menkaure's valley temple "lies at the mouth of the main wadi" (as is clear from maps of the site, as well as personal inspection of the area) which would situate it to receive the brunt of any ephemeral flash floods and hardly is relevant to the western end of the Sphinx enclosure or the body of the Sphinx itself. Furthermore it was apparently finished in mudbrick by Shepseskaf, then rebuilt (after being "flooded" at some point) during the 6th Dynasty. To use an argument from Menkaure's valley temple or the Valley of the Kings at Luxor in an attempt to keep some semblance of the traditional date for the Sphinx, or at least keep it dynastic, just doesn't work.


        Lawton and OgilvieHerald proceed (starting on page 315) to discuss a number of "types of weathering" that they claim are taking place in the Sphinx enclosure, but it quickly becomes evident that they have little understanding of the topic. They discuss what they term "precipitation weathering" (caused by rainfall, as I have elucidated in my various works), "windsand weathering" (also based on my work), and "chemical weathering" (apparently based primarily on the papers of Gauri [see above] and Harrell, 1994, 2000). They divide the latter category into "capillary weathering" (apparently based on ideas from both Gauri and Harrell), "wetsand weathering" (based primarily on the ideas of Harrell), and "atmospheric weathering" (apparently based on the work of both Gauri and Harrell).


Rather than addressing Gauri and Harrell indirectly via a discussion of Lawton and Ogilvie‑Herald's reinterpretation of their ideas, here I will briefly discuss Gauri and Harrell directly.


        K. Lal Gauri has maintained that the weathering and erosion of the Sphinx and walls of the Sphinx enclosure are the result of the various effects of chemical weathering, particularly something known as "exfoliation" or the flaking away of the surface of the limestone. According to Gauri, dew that forms at night on the surface of the rock dissolves soluble salts found on the surface and then the liquid solution is drawn into tiny pores in the rock by capillary action. During the daytime the solution evaporates and salt crystals precipitate in the pores. As the crystals form they exert pressure which causes the surface of the limestone to flake away. This, in fact, is an important weathering factor that is currently taking place on the Giza Plateau. However, it alone cannot account for all of the weathering features seen in the Sphinx enclosure, and more importantly it alone cannot account for the specific distribution of weathering features actually found in the Sphinx enclosure (such as the more intense weathering, erosion, and degradation seen in the western end of the Sphinx enclosure, as discussed further below).


        The weathering processes proposed by Gauri will also have their maximum effect under extreme arid conditions with the Sphinx exposed to the elements. When buried under a layer of sand, the Sphinx and Sphinx enclosure are on the whole protected from these effects. Also, interestingly, the flaking away of the rock as proposed by Gauri is (or at least should be) operating on all of the limestone surfaces of the Giza Plateau, yet somehow virtually no other surfaces show the same type of weathering and erosional profile as seen in the Sphinx enclosure. While I do not deny that salt crystal growth is indeed damaging the Sphinx and other structures during the present day, this mechanism does not explain the ancient degradation patterns observed on the Sphinx's body and in the Sphinx enclosure area but virtually nowhere else on the Giza Plateau.


        Gauri has also suggested that the Sphinx and Sphinx enclosure have been, and are, subject to extremely rapid weathering, and he has pointed out that there has been significant deterioration of the Sphinx since the beginning of the twentieth century. As I have pointed out previously, however, and in all fairness Lawton and OgilvieHerald mention this in their book, one cannot extrapolate present modern weathering rates back into the past when it comes to the Giza Plateau. Industrialization, air pollution, acid rain, rising water tables due to encroaching settlement, tourism, automobile and bus traffic, and so forth, may (I believe are) affecting the structures on the Giza Plateau in a detrimental manner. Modern weathering and erosional processes are not the same as the ancient processes in every case.


        As I have discussed previously in a letter to the magazine "Archaeology" (Schoch,1995a), much of the HawassLehner argument (Hawass and Lehner, 1994; see also Hawass, 1998, and Lehner, 1980, 1985a, 1985b, 1991, 1992a, 1992b, 1997), which is in large part based on the work of Gauri, for a younger Sphinx hinges on the assertion that its present style and rate of weathering and erosion is representative of its past weathering. Hawass and Lehner (1994) have stated that "ancient and modern weathering on the Sphinx are, for the most part, the same ball game." They discuss how soft the limestone is in some places ("you can crumble the stone with your fingertips") and the flaking of the stone to produce "giant potato chips" without realizing that these surficial weathering features are primarily due to modern assaults (pollution, acid deposition, salt deposited by rising water tables from the adjacent village and the damming of the Nile, and so forth) that have not been operating over the last five millennia. The work of K. Lal Gauri has documented the modern deterioration, as opposed to ancient weathering, of the Sphinx. In one publication Gauri illustrates, using comparative photographs from ca. 192526 and ca. 198081, how amazingly rapid this deterioration has been over the span of just a few decades (Gauri and Holdren, 1981). This contradicts the HawassLehner assertion that the ancient and modern weathering are the same. Arguably the Sphinx has suffered more during the last century than it did during the previous 5,000 years.


        It has also been suggested that the Sphinx has been heavily weathered by the action of subsurface ground water being sucked up into the pores of the rock by capillary action (Lawton and OgilvieHerald, page 316). There are a couple of problems with this hypothesis. First, I have yet to see any evidence that this is actually occurring to any significant extent today, much less in the past. If it is a significant factor in producing the weathering profile seen on the Sphinx and in the Sphinx enclosure, then it should also produce the same features (and to the same degree) on rockcut structures carved from the same limestones and at the same elevation or lower found immediately to the south of the Sphinx enclosure. Yet such "capillary weathering" is not evident there. Second, such "capillary weathering," if it does indeed occur to any significant degree in the present day, may well be the result of rising water tables due to sewerage from the adjacent village that has been progressively encroaching on the Giza Plateau.


        James Harrell is the major proponent of the " wetsand" theory to explain the weathering and erosion of the Sphinx and Sphinx enclosure (Harrell, 1994). He has suggested that sand piled up for centuries in the Sphinx enclosure has been wetted by rainfall, Nile floods, and capillary action sucking water up into the overlying sand. Persistent flooding, however, would be expected to cut a wave bench into the Sphinx and the enclosure, and there is no such feature. Also, wet sand around the bottom of the Sphinx enclosure does not explain the obvious and pronounced weathering on the upper portions of the walls of the enclosure. Indeed, the major problem with the wetsand hypothesis is that there is no documented mechanism known by which wet sand piled against a limestone surface will produce the weathering and erosional profile seen on the body of the Sphinx and on the walls of the Sphinx enclosure. Sand, even wet sand (if it ever occurred in the Sphinx enclosure there is no evidence that it did to any significant degree), may actually have served more to promote the preservation of the Sphinx. Furthermore, capillary action, far from being a mechanism cable of keeping numerous feet of piled sand wet over many centuries, is negligible in loose sands in arid areas. Harrell's "wetsand" theory simply does not work as an explanation for the weathering and erosional features of the Sphinx and Sphinx enclosure.


        Lawton and OgilvieHerald (page 320) write "Schoch has emphasized that the enclosure walls are generally more eroded at the top than at the bottom, which appears at odds with the fact that the upper layers tend to be harder. However, Lehner argues that even the relatively uneroded eastern end of the south wall shows that it was deliberately cut with a slope in the original excavation of the enclosure." Thus, Lawton and OgilvieHerald imply that my observations are invalidated. However, as I already pointed out in the 1995 letter to "Archaeology," I have never implied that the walls of the Sphinx enclosure were originally absolutely vertical. In a published illustration (in J. A. West, 1993a, p. 227) I show them at an approximately 80 degree angle before being weathered. However, the fact remains that even taking such a small slope into account the harder layers at the top of the section have been in general eroded back further than softer layers lower in the section, thus corroborating the hypothesis of an older Sphinx.


        On page 320 of their book, as if to put the final "nail" in the coffin of an older Sphinx, Lawton and OgilvieHerald write: "Finally, West and Schoch have increasingly fallen back on the evidence of the deep, rounded, vertical hollows in the west and south walls of the Sphinx enclosure, insisting that these are too ["too" is stressed by being placed in italics by L and OH] obviously weathered by precipitation for the other arguments about weathering to matter. We have sympathy for this view, but again Gauri appears to have an answer. He suggests that they represent faults in the rock originating from the time when the structural deformation of the whole Plateau caused the rock strata to tilt, perhaps millions of years ago, and that they were widened into cavities or channels by the 'hydraulic circulation of the underground water'. They were then exposed when the bedrock was excavated from the Sphinx enclosure." Again, as I pointed out in the 1995 letter to "Archaeology," the limestones of the Giza Plateau are crisscrossed with fractures or joints, and these joints date back millions of years, and possibly some of them may be due to geologic faulting (but see comments by Coxill, 1998, quoted below). However, the joints are not opened up as fissures everywhere on the Giza Plateau. Vertical fissures such as those on the Sphinx enclosure wall can only be produced by water, primarily precipitation, and do bear on the age of the Sphinx. Basically the precipitation runoff follows paths of least resistance and thus works its way into weak joints and fractures. This is dramatically illustrated on the western wall of the Sphinx enclosure and the western portion of the southern wall (which have been subjected to substantial runoff) versus the eastern portion of the southern wall of the enclosure where the fissures are much less extreme; the eastern portion of the enclosure has not taken the brunt of the runoff. My critics, including Gauri, Lehner, Hawass, Lawton, and OgilvieHerald, do not distinguish between naturally occurring joints, on the one hand, and open fissures developed only through weathering processes on the other hand.


        Regarding these socalled "faults," the geologist David Coxill (1998, p. 14) notes: "The subvertical joints . . . are a distinctive characteristic of the surrounding pit [that is, the Sphinx enclosure], and to a somewhat lesser extent, of the Sphinx itself. They are natural fissures in the rock, that were formed by contraction of the carbonate rich sediments, when they were undergoing rockification. These are sedimentologically related fissures and not tectonic faults related to earthquakes, since they do not displace the strata. On the . . . Causeway edge, they are sometimes closed and grouted by fine grained carbonate sediments [a natural process], while others, are open at the top, narrowing, and eventually closing further down the vertical profile of the excavated pit face, and the sphinx's body . . . They represent lines of weakness that have selectively and progressively been exploited by the forces of weathering."


        It is worth quoting Coxill (pages 16‑17), an independent geologist  who has taken the time to study the Sphinx first‑hand,  further on these issues: "[Robert Schoch] presented his findings . . . that the weathering features present [on the body of the Sphinx and in the Sphinx enclosure] are caused by rainfall that has cascaded over the sides of the monument and the surrounding pit . . .


        Other theories have been put forward to try to counter the claim. Lal Gauri et al. (1995) consider that being porous, Member 2 limestone [of which the body of the Sphinx is carved], will suffer from morning dew condensation that dissolves salts within the limestone. When the heat of the day evaporates the water, the salts crystallise out and progressively exert minute pressure weakening the rock and opening up fissures already present. Both they, Hawass, and Lehner (1994), suggest that subsurface water movements, during Eocene times, caused the fissures to open as the water table dropped. This is intriguing, but unlikely to be the case.


        Firstly, condensation affects all monuments in the Giza complex, but very rarely do any show the same type of weathering features of the Sphinx, surrounding pit and cut stone blocks of the Valley Temple.


        Secondly, these weathering features require intense weathering to form their present profile, and, condensation/evaporation is a relatively mild and insignificant form of mechanical weathering in this arid climate.


        Thirdly, fluctuations in the water table do not lead to fissures being produced wider at the top.


        Lal Gauri [et al.] (1995) also suggest that the roundness of the laminars is due to gradational differences in the hardness of the strata. This does not account for variations in the weathering profile, within Member 2 beds, as previously discussed on the Sphinx's body or the presence of open fissures.


        Harrell (1994) suggests that wet sands from Nile floodwaters, and occasional rainfall, would have produced wet sands, leading to these weathering features. That is not acceptable, since floodwaters would have produced a wave cut bench and notch, which would certainly be seen today in the surrounding excavation pit. This is not the case, and again this theory does not satisfactorily explain the presence of erosion features higher up the Sphinx's body and pit face. . . "Therefore, by a process of elimination, it appears that floodwaters and fluctuating ground water levels cannot explain these weathering features, but rainfall does. " Bottom line: Coxill, an independent geologist (as of this writing, I have never met him nor corresponded with him), corroborates my analysis of the nature and agency  responsible for the predominant weathering and erosion seen

in the Sphinx enclosure and on the body of the Sphinx.


        Ian Lawton and Chris OgilvieHerald (pp. 324327), have also criticized my analysis of the seismic data. Unfortunately, they make a number of incorrect assumptions and perpetuate misunderstandings. For instance, Lawton and OgilvieHerald (pp. 324325) claim that I assumed that "the subsurface weathering has been caused by rainfall seeping down through the bedrock floor of the enclosure" when in fact I never postulated that to be the case at all. They then further argue incorrectly that when the Sphinx enclosure is filled with sand, as it has been for much of its existence, the sand will protect the underlying bedrock floor from subsurface weathering. Lawton and OgilvieHerald fail to understand the nature of subsurface weathering. Subsurface weathering is essentially a mineralogical and petrological change in the rocks that proceeds once the rock surface is exposed to the air or atmosphere (such as occurred when the core body of the Sphinx was excavated), no matter what the climate is like. Loose porous sand piled up in the Sphinx enclosure will not significantly protect the bedrock from this type of weathering. This type of weathering is certainly not caused primarily by rainfall collecting on the rock surface and seeping down. It could even be argued that in some cases a moister climate with periods of standing water on the rock that protects the surface from atmospheric exposure may actually result in a slower rate of this form of subsurface weathering than may occur under dryer conditions.


        To further dismiss the seismic data, Lawton and OgilvieHerald go on to claim (page 325) that "it is almost certain that the subsurface erosion has been caused far more by hydraulic and capillary action over the many millennia since the bed was laid down than by relatively recent rainfall and exposure." They are simply wrong. It is subsurface weathering, not erosion (erosion is where the rock is actually carried away), that is under consideration here, and postulating unknown and undocumented mechanisms of "hydraulic and capillary action" as a way to explain the data is essentially meaningless. Furthermore, their explanation of hydraulic and capillary action, quoted above, does not address the discrepancies in subsurface weathering seen within the Sphinx enclosure.


        Concerning the use of the seismic data to date the initial excavation of the Sphinx: It has taken about 4,500 years for the subsurface weathering at the younger, westernmost floor of the Sphinx enclosure to reach a depth of about four feet (assuming that the western end was fully excavated to approximately its present state during Old Kingdom activity at the site). Since the weathering on the other three sides is between 50 and 100 percent deeper, it is reasonable to assume that this excavation is 50 to 100 percent older than the western end. If we accept Khafre's reign as the date for the western enclosure, then this calculation pushes the date for the Great Sphinx's original construction back to approximately the 5000 to 7000 B.C. range.


        I believe this estimate nicely ties in with the climatic history of the Giza Plateau and correlates with the nature and degree of the surface weathering and erosion features. This estimate can be considered a minimum if we assume that weathering rates proceed nonlinearly (the deeper the weathering is, the slower it may progress due to the fact that it is "protected" by the overlying material), and there is the possibility that the very earliest portion of the Sphinx dates back to before 7000 B.C. However, given the known moister conditions on the Giza Plateau prior to the middle third millennium B.C. versus the prevailing aridity since then, some might argue that initial subsurface weathering may possibly (but not necessarily) have been faster than later weathering, and this could counter balance the potential "nonlinear" effect mentioned in the last sentence. In other words, the early moist conditions might, crudely, give deeper weathering which could appear to give it an "older" date but this is countered by the nonlinear nature of the weathering which could appear to give it a "younger" date. In the end, based on many hours of analysis and rumination, I am satisfied that the two opposing factors roughly cancel each other out and a crude linear interpretation of the data is justifiable. In this manner, I return to my estimate of circa 5000 to 7000 B.C. for the oldest portion of the Sphinx, a date that is corroborated by the correlation between the nature of the weathering in the Sphinx enclosure and the paleoclimatic history of the region.


        Lawton and OgilvieHerald (page 326) state that "Schoch himself accepts the existence of New Kingdom repair blocks on the rump ["rump" is stressed by being placed in italics by L and OH] of the monument, indicating that extensive weathering had taken place at the back since the orthodox carving date. So why could this rate of weathering not have applied all over?" This is a dishonest statement. From my original 1992 KMT article to my 1999 book VOICES OF THE ROCKS I have pointed out the disagreement among Egyptologists (such as Lehner and Hawass) as to whether the earliest repairs to the Sphinx date to the Old Kingdom or New Kingdom. I have never definitively "accepted" any particular date for them, although I tend to suspect that Hawass is correct and they are indeed Old Kingdom. Furthermore, I've made no statement nor judgement concerning the age of any repairs on the very westernmost end of the core body of the Sphinx in the vicinity of where we ran our seismic line. Indeed, this area is currently covered at ground level with twentiethcentury repair blocks that obscure any ancient repairs, and furthermore, evidence of New Kingdom repairs there (if they existed) would not invalidate the concept of an older Sphinx. It is well known that the Sphinx has been refurbished and reworked many times over the centuries. New Kingdom repairs could easily have replaced Old Kingdom repairs, and of course not all repairs from all time periods cover or repair equal amounts of damage as Lawton and OgilvieHerald imply in the quote above.


        Lawton and OgilvieHerald go on to state (page 326) that "it is clear that the west wall [of the Sphinx enclosure] behind the rump [of the Sphinx] which according to Schoch's theory must have been carved only c. 2500 BC shows exactly the same vertical and rounded profiles as the [presumably older] south wall. ["shows . . . south wall" is stressed by being placed in italics by L and OH]" They therefore conclude that this obvious contradiction refutes my analysis. Actually it does nothing of the kind. Lawton and OgilvieHerald fail to mention that two "back walls" lie behind the rump of the Sphinx. The higher "back wall," which lies farther to the west, does indeed show rain weathering ("vertical and rounded profiles") and dates back to pre Old Kingdom times. The seismic studies indicate that the lower "back wall," set directly behind the rump of the Sphinx and lacking the "vertical and rounded profiles," may have been excavated much later, possibly in Khafre's time (circa 2500 B.C.), when I believe the rump of the Sphinx was reworked and possibly at that time carved down to the same level as the floor of the Sphinx enclosure on the other three sides of the sculpture. I discuss this issue explicitly in my 1992 KMT paper titled "Redating the Great Sphinx of Giza" (see especially page 57).


        These same authors argue against the twostage construction of the socalled Valley and Sphinx temples, pointing out that some granite blocks have actually been worked into the Valley Temple and underlie an uppermost course of limestone blocks (page 331). Likewise, Old Kingdom pottery fragments have been found around and under detached limestone blocks of the Sphinx Temple (page 334). This evidence they take to "prove" that the temples, and therefore the Sphinx itself, must date to Khafre's time. However, it is perfectly conceivable, in fact to be expected, that Old Kingdom artifacts would be found around the temples and newer (that is, Old Kingdom) granite blocks would be incorporated into the actual temples during the rebuilding and refurbishing phase of Khafre's time. Clearly, there was much activity on the Giza Plateau during the Fourth Dynasty, and we should expect to find the remains of that activity.


        Harrell has published various comments on the Internet concerning the geological evidence for the age of the Sphinx (Harrell, 2000). When I first read the latest comments by James Harrell, I immediately said to myself “here we go again.” Essentially, he is recycling some of the same tired arguments and misunderstandings, which have already been discussed and falsified in the literature, while adding further to the misconceptions.


        In his opening paragraph Harrell claims that geologist Colin Reader “with slight modification” supports the dating of the Great Sphinx to the Fourth Dynasty, when in fact according to Reader the “excavation of the Sphinx” should be “tentatively placed sometime in the latter half of the Early Dynastic Period” or, in other words, in the Second or Third Dynasty (Reader, 1998; see further discussion of Reader’s paper below). Yes, Harrell later clarifies that Reader does not exactly agree with Harrell's date, but the way he first presents Reader as agreeing with a Khafre and Fourth Dynasty date is inherently deceptive. That “slight modification” of Reader's dating makes all the difference in the world. I may not fully agree with Reader's conclusions as to the absolute dating of the earliest portions of the Sphinx, but I do believe that Reader's meticulous study (Harrell's off-hand and anecdotal comments should not be allowed to detract from the importance of Reader's careful study) clearly establishes that the origins of the Great Sphinx are pre-Khufu. In fact, that is the crux of the debate over the age of the Great Sphinx as far as I am concerned. Is it Old Kingdom (i.e., Khufu-Khafre times) or earlier? A secondary question is: If it is pre-Old Kingdom, how much older is it? In my opinion, Reader has established that the Great Sphinx is pre-Old Kingdom, so now the focus should turn to the question of how much older than Old Kingdom.


        Harrell asserts that I have dated the Great Sphinx to 7,000+ B.C., when in fact, even though I do not absolutely rule out such an early date, I have stated on numerous occasions that I believe the geological evidence is quite compatible with a date of 5,000 to 7,000 B.C. However, I am not adamant about these dates whatsoever. For me, the important issue is whether or not the Sphinx is pre-Old Kingdom. I would note here, though, that my dating of 5,000 to 7,000 B.C. is partially based on an analysis of the seismic work that was carried out on the Giza Plateau with Thomas Dobecki (see comments above).


        Contra Harrell, the low-velocity layer found under the floor of the Sphinx enclosure does not follow the bedding of the strata. The strike and dip of the limestone layers, as well as their composition, are clearly visible by observing the sides of the Sphinx enclosure. The differential weathering pattern that we recorded in the subsurface cuts across the dip of the strata and parallels the floor of the enclosure (as is to be expected of weathering). Furthermore, the dramatically shallower depth of the low-velocity layer immediately behind the rump of the Sphinx is totally incompatible with the notion that the seismic data simply records original bedding in the limestone. It is consistent, however, with the reconstructed scenario of the excavation of the Sphinx in stages that I have proposed. I am not simply mistaking a “shoal-reef facies” for a subsurface weathered zone and a “nummulite bank” limestone facies for unweathered subsurface limestone, as Harrell suggests.


        Harrell asks how I know that the low-velocity layer seen under the floor of the Sphinx enclosure represents weathered limestone. He then goes on to state that “Nowhere has he [Schoch] ever given any evidence to support this claim. He has not dug or drilled into this layer and so has no idea of what is really down there.” Actually, this is not quite true (although I would add that, by the same token, Harrell “has no idea of what is really down there”). First, one can obviously observe the rock currently exposed on the surface of the floor of the Sphinx enclosure, and it is weathered limestone (and it should be, even according to Harrell's bogus “wet sand” hypothesis discussed further below). It is very strange to argue that the observed surface is weathered, yet the subsurface is unweathered, despite no differences in seismic velocities; this just does not make sense. I fail to understand Harrell's convoluted reasoning. Second, if Harrell had ever read the Geoarchaeology paper that Dobecki and I published (cited above), he would have noticed that several short seismic lines (lines S5, S6, S7, and S8) were run just north of the Great Sphinx on the terrace area in order to acquire velocities on undoubted disintegrated remains of the Setepet Member (the limestones of which much of the body of the Sphinx is composed) and the weathered Rosetau Member (which forms the lowest-most portions of the Sphinx and the floor of the Sphinx enclosure). In this area one can acquire both seismic data and look at the layers in cross-section (since the rock has been exposed as a nice vertical profile along the northern wall of the Sphinx enclosure). The Rosetau Member is weathered and we recorded velocities compatible with a weathered layer on the terrace. Similar velocities were recorded in the Rosetau Member under the floor of the Sphinx enclosure. The most parsimonious explanation is that the low-velocity layer represents a weathered zone, rather that hypothesize that it is following “original bedding” when the evidence is actually counter to such an interpretation. I stand by our analysis of the seismic data.


        Concerning the surficial weathering and erosion observed on the body of the Sphinx and on the walls of the Sphinx enclosure, this has been discussed at length in many other places (see especially Reader, 1998). Harrell's “wet sand” hypothesis has no basis in reality, and in my opinion does not merit further discussion at the moment (see comments above). As far as I can determine, the “wet sand” hypothesis was invented simply to explain away the degradation features seen in the Sphinx enclosure. There is no evidence that either there was wet sand in the Sphinx enclosure for long periods of time or that such wet sand would cause the degradation patterns actually observed. Let it be said here that if there was any truth to Harrell's “wet sand” hypothesis or similar ad hoc hypotheses formulated to simply explain-away the surface weathering and erosional features observed on the Sphinx and in the Sphinx enclosure, then similar weathering and erosional features (similar in both nature and degree) should be observed on and in numerous Old Kingdom shaft tombs and other structures found on the Giza Plateau, but they are absent.


        Harrell invokes climatic records from the past century to demonstrate that the Giza Plateau is rained upon periodically. Of course it is; that is hardly the issue. He also, less convincingly, argues that a sand-filled enclosure that is rained upon will remain wet for “many weeks or months due to capillary retention.” Actually, this is quite questionable (I don't believe there is any evidence to support Harrell's scenario along these lines), but in many ways it is beside the point. The real issue is whether wet sand piled against the limestone face will result in the degradation features and their distribution as actually observed in the Sphinx enclosure. I contend that the answer is no. Possibly wet sand against the limestone surface might result in some weathering of the rock, but it is uncertain to what degree. More importantly, wet sand piled against the limestone surface would probably protect the surface and impede the erosion of the rock (the actual carrying away of material), yet it is this pronounced erosion that is so prominent and important in the analysis of the degradation features seen in the Sphinx enclosure. Harrell's “wet sand” hypothesis cannot account for these features.


        What can account for these features is surface rainfall runoff in pre-Khufu times, as so well elucidated by Reader's analysis (1998; see below). Harrell attempts to counter Reader's analysis by claiming, based on admittedly anecdotal evidence, that rainfall runoff still reaches the Sphinx enclosure and thus the degradation features observed today could have formed, according to Harrell, over the last 4,500 years. This, however, is despite the fact that Harrell states that he thinks “it is now universally agreed that the Sphinx spent most of its 4,500 year history buried in sand... ” and, as discussed above, it is not at all evident that the observed degradation features would even form when the Sphinx enclosure is filled with sand.


        More importantly, however, is the fact that Harrell has no real handle on how much surface runoff there is now, or was in the past, or how it might actually degrade the limestones. His whole scenario is based on one anecdotal observation of a “torrent of water cascading into the enclosure during a rain storm”  one night in 1990 or 1991. Exactly how much water (this might be difficult to observe at night during a sound-and-light show), why it was cascading (there has been much modern modification of the Giza Plateau),what effects it had on the stone, and so forth, are all open questions. Harrell's musings should not be considered to invalidate the serious geological investigations that have been undertaken on the Giza Plateau.


        Harrell goes on to suggest that surface rainfall runoff is not really that important anyway, and states his belief that much of any rainfall will “sink into the limestone through its myriad fractures (joints) and then travel through these as well as along the bedding planes between the limestone layers.” This hypothesis, of course, counters his previous anecdotal evidence concerning a “torrent of water cascading into the enclosure during a rain storm.” To be blunt, I don't believe Harrell has any evidence that this is the case - - it is pure speculation on his part. It is important for Harrell to hypothesize this, however, if he wants to retain the traditional attribution of the Great Sphinx to Khafre of the Fourth Dynasty. Reader has made a strong case that surface runoff was responsible for the specific degradation features and their distribution seen in the Sphinx enclosure, and there was not sufficient runoff after the quarrying work done in conjunction with Khufu's pyramid (the Khufu quarry would have impeded surface runoff toward and into the Sphinx enclosure) to account for the pattern of degradation. Harrell argues (what he calls an “educated guess”): “The Khufu quarry would be no barrier to the subsurface flow of water and might even serve to collect the surface runoff and then channel it through the limestone on the west side of the Sphinx enclosure. I [i.e., Harrell] would expect it to emerge on the western walls as springlike seepages along the bedding planes.” In fact, there is no evidence for such a process. I have studied the western wall of the Sphinx enclosure closely and I have observed no signs of such spring-like seepages, either in the recent or distant past. Indeed, this type of water flow through and over the limestones of the Giza Plateau would give a very different pattern of degradation than is actually observed. Simply put, the evidence does not support Harrell's “educated guess” whereas it does support Reader's analysis. Unfortunately for Harrell and traditional Egyptologists, the evidence is not compatible with the traditional attribution of the Great Sphinx to Khafre, circa 2500 B.C.





        Two important geological studies have recently been carried out that go a long way toward supporting my basic analyses concerning the origins and history of the Great Sphinx. The first study, by the geologist David Coxill (1998), has already been mentioned and quoted above. After confirming my observations on the weathering and erosion of the Sphinx, and pointing out that other explanations (for instance, as proposed by Gauri and Harrell) do not work, Coxill clearly states (page 17): "This [the data and analysis he covers in the preceding portions of his paper] implies that the Sphinx is at least 5,000 years old and predates dynastic times." Coxill then discusses very briefly the seismic work that Thomas Dobecki and I pursued and my estimate of an initial date of 5,000 to 7,000 B.C. for the earliest parts of the Sphinx based on the seismic data. He neither supports nor refutes this portion of my work, but simply writes (page 17): "Absolute dates for the sculpturing of the Sphinx should be taken with extreme caution and therefore dates should be as conservative as possible ‑‑ until more conclusive evidence comes to light." I can understand that he could take this stance, although perhaps I feel more comfortable with, and confident in, the seismic analysis we did. Coxill, in the next paragraph of his paper (page 17), continues: "Nevertheless, it [the Sphinx] is clearly older than the traditional date for the origins of the Sphinx ‑‑ in the reign of Khafre, 25202490 BC."


        Another geologist, Colin Reader, has also pursued a meticulous study of weathering and erosion (degradation) features on the body of the Sphinx and in the Sphinx enclosure. This he has combined with a detailed analysis of the ancient hydrology of the Giza Plateau. Although as of this writing, his research has apparently not been formally published in journal or book form, Reader has been circulating his work as an illustrated paper entitled "Khufu Knew the Sphinx" (the copy I received from him is dated July 1998). Like Coxill, Reader points out the problems and weaknesses in the arguments of my opponents. Reader notes (quoted from the summary of his paper; no page number), that there is "a marked increase in the intensity of the degradation [that is, weathering and erosion] towards the west [western end] of the Sphinx enclosure." Reader continues, "In my opinion, the only mechanism that can fully explain this increase in intensity is the action of rainfall runoff discharging into the Sphinx enclosure from the higher plateau in the north and west . . . However, large quarries worked during the reign of Khufu [a predecessor of Khafre, the "traditional" builder of the Sphinx] and located immediately upslope, will have prevented any significant runoff reaching the Sphinx." Thus Reader concludes (page 11 of his paper) that "When considered in terms of the hydrology of the site, the distribution of degradation within the Sphinx enclosure indicates that the excavation of the Sphinx predates Khufu's early Fourth Dynasty development at Giza." Interestingly, Reader also concludes that the socalled "Khafre's" causeway (running from the area of the Sphinx , Sphinx Temple, and Khafre Valley Temple up to the Mortuary Temple on the eastern side of the Khafre pyramid), part of "Khafre's" Mortuary Temple (which Reader refers to as the "Protomortuary temple"), and the Sphinx Temple predate the reign of Khufu.


        As I have discussed in my book, VOICES OF THE ROCKS (Schoch with McNally, 1999, 2000), I have come out strongly in favor of not only an older Sphinx, but also a contemporaneous (thus older) Sphinx Temple (at least the limestone core being older than the Fourth Dynasty). Independently of Reader, John Anthony West and I have also concluded that part of "Khafre's" Mortuary Temple predates Khafre. Reader has now come to the same conclusion concerning "Khafre's" Mortuary Temple. I am pleased to see his confirmation.


        One should note that Reader clearly accepts the Sphinx Temple as predating Khufu, and if it is correct that the Valley Temple was constructed from limestone blocks that came out of the Sphinx enclosure at a higher level than the blocks that were used to build the Sphinx Temple (as clearly stated by Lawton and OgilvieHerald in their book on page 329; I believe they may be correct here), then the Valley Temple must also be preKhufu (as West and I have hypothesized and advocated all along).


        Reader tentatively dates the "excavation of the Sphinx" and the construction of the Sphinx Temple, ProtoMortuary Temple, and "Khafre's" causeway to "sometime in the latter half of the Early Dynastic Period [page 11]" (that is, circa 2800 to 2600 B.C. or so) on the basis of "the known use of stone in ancient Egyptian architecture [page 8]." I believe that Reader's estimated date for the excavation of the earliest portions of the Sphinx is later than the evidence indicates. I would make three general points:


1) In my opinion, the nature and degree of weathering and erosion (degradation) on the Sphinx and in the Sphinx enclosure is much different than what would be expected if the Sphinx had not been carved until 2800 B.C., or even 3000 B.C. Also, mudbrick mastabas on the Saqqara Plateau, dated to circa 2800 B.C., show no evidence of significant rain weathering, indicating just how dry the climate has been for the last 5,000 years. I continue to believe that the erosional features on the Sphinx and in the Sphinx enclosure indicate a much earlier date than 3000 or 2800 B.C. It strains credulity to believe that the amount, type, and degree of precipitationinduced erosion seen in the Sphinx enclosure was produced in only a few centuries.


2) In his July 1998 paper Reader never addresses the seismic work that we pursued around the Sphinx, which is in part the basis I used to calibrate a crude estimate for the age of the earliest excavations in the Sphinx enclosure. In my opinion, the date estimate based on our seismic work is compatible with the type and amount of erosion and weathering seen in the Sphinx enclosure, and also nicely correlates with the known paleoclimatic history of the Giza Plateau.


3) I do not find dating the Sphinx on the basis of "the known use of stone in ancient Egyptian architecture" convincing. I would point out that massive stonework erections were being carried out millennia earlier than circa 2800 B.C. in other parts of the Mediterranean (for instance, at Jericho in Palestine). Even in Egypt, it is now acknowledged that megalithic structures were being erected at Nabta (west of Abu Simbel in Upper Egypt; discussed in the text of my book, VOICES) by the fifth millennium B.C. and the predynastic "Libyan palette" (circa 31003000 B.C.), now housed in the Cairo Museum, records fortified cities (which may well have included architectural stonework) along the western edge of the Nile delta at a very early date. I find it quite conceivable that architectural stonework was being pursued at Giza prior to 2800 or 3000 B.C.


        Reader suggests that the head of the Sphinx may have originally been a prominent rock outlier that was first carved into some type of head (perhaps initially a lion, Reader suggests likewise, J. A. West and I hypothesized that the Sphinx may have originally been a lion in the 1993 video "The Mystery of the Sphinx" )and later recarved. Independently, I have come to similar conclusions relative to the head of the Sphinx once having been a prominent rock outlier, and I have stated so publicly. In my 1992 KMT paper I point out that while Farouk ElBaz's yardang (natural windshaped hill) hypothesis for the Sphinx as a whole is untenable (see El-Baz, 1981, 1982), the head may have originally been a yardang (which would mean that it was some kind of rock outlier), but it is too heavily modified by carving and recarving to know for certain.


        As far as I am concerned, Reader is one more geologist who has corroborated my basic observations and conclusions. The oldest portions of the Sphinx date back to a period well before circa 2500 B.C.




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Egyptian Antiquities Organization, 1992, The First International Symposium on the Great Sphinx:  Towards Global Treatment of the Sphinx.  Cairo, 29 February - 3 March 1992.  Prospectus, Programme, and Abstracts.  Ministry of Culture, Egyptian Antiquities Organization, Cairo.


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El-Baz, F., 1982, Egypt's desert of promise.  National Geographic, February, 1982, pp. 190-221.



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Gauri, K., 1984, Geologic study of the Sphinx.  American Research Center in Egypt Newsletter, Number 127, pp. 24-43.


Gauri, K. Lal, 1992, How old is the Sphinx?, Abstracts for the 1992 Annual Meeting of the American Association for the Advancement of Science, Chicago, p. 202.


Gauri, K. L., A. N. Chowdhury, N. P. Kulshreshtha, and A. R. Punuru, 1988, Geologic features and durability of limestones at the Sphinx, in Engineering Geology of Ancient Works, Monuments and Historical Sites (P. G. Marinos and G. C. Koukis, eds.), A. A. Balkema, Rotterdam, pp. 723-729.


Gauri, K., and G. C. Holdren, 1981, Deterioration of the stone of  the Great Sphinx.  American Research Center in Egypt Newsletter, Number 114, pp. 35-47.


Gauri, K. Lal, G. C. Holdren, and W. C. Vaughan, 1986, Cleaning Efflorescences from Masonry, in Cleaning Stone and Masonry (J. R. Clifton, ed.), American Society for Testing and Materials, Philadelphia, pp. 3-13.


Gauri, K. Lal, and A. R. Punuru, 1989, Characterization and durability of limestones determined through mercury intrusion porosimetry.  The Conservation of Monuments in the Mediterranean Basin (F. Zerra, ed.),  Proc. First Intern. Sympos. Bari, 1989, pp. 255-258.


Gauri, K. Lal, J. Sinai, and J. A. Bandyopadhyay, 1995, "Geologic Weathering and Its Implications on the Age of the Sphinx."  Geoarchaeology, 10, no. 2, pp. 119-133.


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Harrell, J. A., 2000, “Comments on the Geological Evidence for the Sphinx’s Age” Internet/WWW.  Available at:  13 March 2000.


Hamblin, D. J., 1986, A unique approach to unraveling the secrets of the Great Pyramids [article about the work of M. Lehner], Smithsonian, April 1986, pp. 78-93.


Hassan, S., 1949, The Sphinx:  Its History in the Light of Recent Excavations.  Government Press, Cairo.


Hawass, Z., 1990, The Pyramids of Ancient Egypt.  Carnegie Museum of Natural History, Pittsburgh.


Hawass, Z., 1992, History of the Sphinx Conservation, in The First International Symposium on the Great Sphinx:  Towards Global Treatment of the Sphinx.  Cairo, 29 February - 3 March 1992.  Prospectus, Programme, and Abstracts.  Ministry of Culture, Egyptian Antiquities Organization, Cairo, p. 14.


Hawass, Z., 1998, The Secrets of the Sphinx: Restoration Past and Present.  Cairo: The American University in Cairo Press.


Hawass, Z., and M. Lehner, 1994, The Sphinx: Who built it and why?  Archaeology, vol. 47, no. 5, pp. 30-47.


Hayes, W. C., 1965, Most Ancient Egypt, edited by K. C. Seele.  The University of Chicago Press, Chicago.


Hedges, C., 1992, Sphinx poses riddle about its own fate: Experts ponder ways to save monument from man and time.  The New York Times, 10 March 1992, p. C4.


Hillel, D. J., 1991, Out of the Earth:  Civilization and the Life of the Soil.  The Free Press (A Division of Macmillan, Inc.), New York.


Holmes, D. L., 1989, The Predynastic Lithic Industries of Upper Egypt:  A Comparative Study of the Lithic Traditions of Badari, Nagada and Hierakonpolis.  Part ii.  Cambridge Monographs in African Archaeology 33, BAR International Series 469 (ii), Oxford.


Issawi, B., 1992, Contribution to the Study of Geology of the Sphinx Area -- Giza Egypt, in The First International Symposium on the Great Sphinx:  Towards Global Treatment of the Sphinx.  Cairo, 29 February - 3 March 1992.  Prospectus, Programme, and Abstracts.  Ministry of Culture, Egyptian Antiquities Organization, Cairo, p. 17.


Lawton, I., and C. Ogilvie-Herald, 1999,  Giza: The Truth: The People, Politics and History Behind the World’s Most Famous Archaeological Site.  London: Virgin Publishing.


Lehner, M., 1980, The ARCE Sphinx project:  A preliminary report.  American Research Center in Egypt Newsletter, Number 112, pp. 3-33.


Lehner, M. 1985a, The development of the Giza Necropolis:  The Khufu Project.  Mitt. des Deutschen Archaologischen Inst., Cairo, Abt., 41:109-143.


Lehner, M. [interview by A. R. Smith], 1985b, The Search for Ra Ta.  Venture Inward [magazine of the Association for Research and Enlightenment and The Edgar Cayce Foundation], January/February 1985, pp. 6-11, 47; March/April 1985, pp. 6-11.


Lehner, M., 1991, Computer rebuilds the Ancient Sphinx.  National Geographic, April 1991, pp. 32-39.


Lehner, M., 1992a, How old is the Sphinx?, Abstracts for the 1992 Annual Meeting of the American Association for the Advancement of Science, Chicago, p. 202.


Lehner, M., 1992b, Reconstructing the Sphinx.  Cambridge Archaeological Journal 2 (1), 3-26.


Lehner, M., 1997,  The Complete Pyramids: Solving the Ancient Mysteries.  Thames and Hudson, London.


Moore, S., 1992, Riddles of the Sphinx.  Fortean Times, Number 64 (August/September 1992), p. 42.


Needler, W., 1984, Predynastic and Archaic Egypt in The Brooklyn Museum.  The Brooklyn Museum, New York.


Payn, M., 1992,  Sphinx redate response.  KMT, A Modern Journal of Ancient Egypt, vol. 3, no. 3 (Fall 1992), p. 3.


Punuru, A. R., A. N. Chowdhury, N. J. Kulshreshtha, and K. L. Gauri, 1990, Control of porosity on durability of limestone at the Great Sphinx, Egypt.  Environ. Geol. Water Sci., 15:225-232.


Reader, C., 1998, "Khufu Knew the Sphinx: A Reconciliation of the Geological and Archaeological Evidence for the Age of the Sphinx and a Revised Sequence of Development for the Giza Necropolis."  Unpublished.  July 1998.


Said, R., ed., 1990, The Geology of Egypt.  A. A. Balkema, Rotterdam.  [see especially Chapter 2, "Geomorphology" by R. Said, pp. 9-25; Chapter 17, "Nile Delta" by J. C. Harms and            J. L. Wray, pp. 329-343; Chapter 24, "Cenozoic" by R. Said, pp. 451-486; and Chapter 25, "Quaternary" by R. Said, pp. 487-507.]


Said, R., and L. Martin, 1964, Cairo Area geological excursion notes, in Guidebook to the Geology and Archaeology of Egypt (F. A. Reilly, ed.), Petroleum Exploration Society of Libya, Sixth Annual Field Conference, pp. 107-121.


Schoch, R. M. [interview by A. R. Smith], 1992a, The Sphinx: Older by Half?  Venture Inward [magazine of the Association for Research and Enlightenment and The Edgar Cayce Foundation], January/February 1992, pp. 14-17, 48-49.


Schoch, R. M., 1992b, How old is the Sphinx?, Abstracts for the 1992 Annual Meeting of the American Association for the Advancement of Science, Chicago, p. 202.


Schoch, R. M., 1992c, Scholars debate age of the Great Sphinx [Letter].  The Chronicle of Higher Education, 15 January 1992, p. B5.

Schoch, R. M., 1992d, Redating the Great Sphinx of Giza.  KMT, A Modern Journal of Ancient Egypt, vol. 3, no. 2 (Summer 1992), pp. 52-59, 66-70.


Schoch, R. M., 1992e, A modern riddle of the Sphinx.  OMNI, v. 14, no. 11 (August 1992), pp. 46-48, 68-69.


Schoch, R. M., 1993a, Reconsidering the Sphinx.  OMNI, v. 15, no. 6 (April 1993), p. 31.


Schoch, R. M., 1993b, Dating the Sphinx.  Cond Nast Traveler, v. 28, no. 2 (February 1993), p. 103.


Schoch, R. M., 1994a, “L'Age du Sphinx de Gizeh:  Vers Une Revision Dechirante?” Kadath, Chroniques des Civilisations Disparues, No. 81 (Winter 1993-1994), pp. 13-53.


Schoch, R. M., 1994b, “[On the Geological Evidence for an Older Sphinx].”  KMT, A Modern Journal of Ancient Egypt, v. 5, no. 2 (Summer 1994), pp. 6-7.


Schoch, R. M., 1995a, “Sphinx Links.”  Archaeology, vol. 48, no. 1 (January/February 1995), pp. 10-12.


Schoch, R. M., 1995b, “The Great Sphinx Controversy.”  Fortean Times, Number 79 (February-March, 1995), pp. 34-39.


Schoch, R. M., 2000, New Studies Confirm Very Old Sphinx.  Atlantis Rising, Number 23 (May 2000), pp. 39, 41, 68, 69.


Schoch, Robert M., with Robert Aquinas McNally, 1999, Voices of the Rocks: A Scientist Looks at Catastrophes & Ancient Civilizations.  Harmony Books, New York. 


Schoch, Robert M., with Robert Aquinas McNally, 2000,  “Epilogue: An Update to the Redating of the Sphinx, and other Pertinent Matters” IN Voices of the Rocks: Lost Civilizations and the Catastrophes that Destroyed Them, by Robert M. Schoch, with Robert Aquinas McNally (UK edition of “Voices of the Rocks”), pp. 243-249.  Thorsons, London.


Schoch, R. M., and J. A. West, 1991, Redating the Great Sphinx of Giza, Egypt.  Geological Society of America, abstracts with programs, vol. 23, no. 5, p. A253.


Schwaller de Lubicz, R. A., 1982 [translated by A. and G. VandenBroeck], Sacred Science:  The King of Pharaonic Theocracy.  Inner Traditions International, New York.


Vreeken, W. J., 1984, Relative dating of soils and paleosols, in Quaternary Dating Methods (W. C. Mahaney, ed.), Elsevier, Amsterdam, pp. 269-281.


West, J. A., 1979, Serpent in the Sky:  The High Wisdom of Ancient Egypt.  Harper and Row, New York.


West, J. A., 1987, Serpent in the Sky:  The High Wisdom of Ancient Egypt (second edition).  Julian Press, New York.


West, J. A., 1989, The Traveler's Key to Ancient Egypt.  Alfred A. Knopf, New York.


West, J. A., 1992, The case of the missing pharaoh.  The New York Times, 27 June 1992, p. 23.


West, J. A., 1993a, Serpent in the Sky:  The High Wisdom of Ancient Egypt (revised edition).  Quest Books, Wheaton, Il.


West, J. A., 1993b, Civilization Rethought. Conde Nast Traveler v. 28, no. 2 (February 1993), pp. 100-105, 168-171, 175-177.


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