The problems with the ‘wet-sand hypothesis’, as I perceive them, are discussed in the introduction and accompanying notes of my original paper². In his recent paper¹¹, Harrell retracts high Nile inundation as one of the mechanisms for wetting the sand in the Sphinx enclosure, but re-confirms his view that the Sphinx is attributable to Khafre and, specifically, that the degradation within the Sphinx enclosure can be fully interpreted in terms of the climatic conditions which have prevailed over the last 4500 years.

Harrell confirms my observations that the intensity of degradation within the Sphinx enclosure is greatest along the western walls (observations that do not appear to have been noted by any other author in the original debate). However, Harrell rejects my hypothesis that, before Khufu’s quarrying, the sloping Giza plateau would have directed surface run-off at the Sphinx enclosure. He also rejects my argument that Khufu’s quarrying brought an end to this run-off and, therefore, an end to erosion within the Sphinx enclosure. Harrell bases these objections on three primary points:

Unfortunately for Harrell’s argument there is a major contradiction inherent in these objections. His statement that run-off can be observed today does not sit particularly well with his second point that, as rainfall would infiltrate the exposed limestones, run-off would not be generated at Giza. This contradiction is maintained when later in his March 2000 paper, Harrell returns to run-off as one of the primary methods by which sand within the Sphinx enclosure will have become wet. Harrell presents a line of reasoning which I have maintained throughout, stating:

Notwithstanding these contradictions, I readily accept that Giza continues to experience significant rainfall, with annual totals (in the order of 0.5m) recorded in Cairo today. With respect to his first point, following an editorial qualification posted by Ian Lawton on the G:TT website, it now appears that the anecdotal evidence cited by Harrell actually refers to run-off from the south western corner of the Sphinx enclosure only and may be associated with Khafre’s causeway.

With respect to Harrell’s second and third points, I have two fundamental objections to this line of argument. My first objection is that, if rainfall infiltrates the surface limestones why would it not infiltrate the limestones that form the base of the quarry? Secondly, as discussed by Lehner in his seminal paper The Development of the Giza Necropolis: The Khufu Project¹³, the base of Khufu’s quarries reach up to 30m deep (approx 10m above sea level), lower than the base of the Sphinx enclosure (approx 20m asl). Any sub-surface flow from the base of the quarries is likely, therefore, to pass beneath the Sphinx enclosure, rather than emerge as a series of springs in the face of the western enclosure wall, as Harrell suggests.

Notwithstanding this, it is my opinion that the degradation of the Sphinx enclosure is not consistent with what would be expected from the mechanism described by Harrell. If sub-surface flow emerged as spring lines in the western face of the Sphinx enclosure, a series of open, solution cavities (Karstic features seen elsewhere at Giza) would be evident emerging from deep into the limestone. These features, if present at all, do not dominate the western Sphinx enclosure walls. In fact the most significant degradation consists of the deep sub-vertical features and rounded or coved appearance to the rocks, features that are so typical of surface erosion by flowing water.

Having ‘disposed’ of my argument, Harrell then goes on to describe the work of Gauri et al¹⁴, fellow advocates of the conventional Fourth Dynasty age of the Sphinx. Gauri attributes the degradation of the Sphinx to chemical weathering and exfoliation, a process that Harrell views as complimentary to his own ‘wet-sand’ hypothesis. Whilst I accept that Gauri’s chemical weathering has affected the exposed limestones within the Sphinx enclosure, in my July 1999 paper², I discussed at length the limitations of this process, indicating that it fails to explain the more intense degradation of the western Sphinx enclosure walls.

Both chemical weathering and wet sand are considered by their respective authors to have been particularly active up to the present day and are the cause, they believe, of the more intense degradation in the western Sphinx enclosure. On this basis they argue that it is not necessary for the Sphinx to have been built before the Fourth Dynasty. The evidence from the site, however, is that the processes that led to the more intense degradation of the Sphinx enclosure, are not currently active and have not been experienced for at least the past 2500 years.

This evidence comes from a number of 26^th Dynasty tombs (ca 600BC) located close to, and in a similar hydrogeological setting to, the Sphinx. The first of these tombs is the so-called ‘Campbell’s tomb’ a square-sectioned shaft tomb located a short distance to the west (up slope) of the Sphinx enclosure, between the Sphinx and the backfilled Khufu quarry. Like the Sphinx enclosure, Campbell’s tomb was filled with sand, only being cleared in the 1830s. If rain from the quarried plateau was responsible for the continuing wetting of accumulated sand and for the degradation of the Sphinx enclosure, as Harrell argues, features of erosion similar to those in the west of the Sphinx enclosure would be expected on the western walls of Campbell’s tomb. Such features are not, however, present. Some may argue that the difference in degradation is simply due to the Sphinx being the older of the two monuments, however, it is not the intensity, but the nature of the degradation that is so markedly different, with the exposed limestone in Campbell’s tomb showing not even the slightest evidence of the coved appearance that characterises the western Sphinx enclosure walls.

There is, however, even stronger evidence that the processes that led to the degradation of the western Sphinx enclosure are not active today and have not been active since the 26^th Dynasty. Three 26^th Dynasty tombs have been cut into the limestone beds exposed along the western enclosure wall. Although the strata into which these tombs were cut are intensely degraded, the tomb portals still show extensive chisel marks made during their excavation, evidence that recent degradation has not be particularly aggressive. These portals are exposed to direct sunlight for much of the day and, as with the Sphinx, they were buried in sand for long periods of time. If chemical weathering or Harrell’s wet sand hypothesis had been significant agents of degradation, it is without doubt that the portals of these tombs would have been affected. It is quite clear, therefore, that the intense degradation of the Sphinx enclosure walls can not be attributed to any degradational processes that have been active since 600BC.

It is possible to extend this argument even further back in time. According to the well-respected and widely accepted reconstruction of the climate, established by Karl Butzer¹⁵, the weather conditions experienced today at Giza have not changed significantly since ca. 2350BC (towards the end of the Fifth Dynasty). If the rounded features of degradation that characterise the western Sphinx enclosure have not developed since the 26^th Dynasty, there is no reason to believe that they would have developed during the period between the 26^th Dynasty and the end of the Fifth Dynasty, particularly, as Butzer has stated, the climatic conditions have changed very little during this time.

The evidence from the 26^th Dynasty tombs suggests, therefore, that neither chemical weathering, wet sand or rainfall have been responsible for the intense degradation of the limestone exposed in the western Sphinx enclosure and that the erosion present must have developed under a different degradational regime. I consider that the most significant change to the degradational regime at Giza came with the excavation of Khufu’s quarries, which brought an end to the possibility that rainfall run-off could discharge into the western Sphinx enclosure.

Finally, Harrell also objects to my pre-Fourth Dynasty attribution for the alignment of ‘Khafre’s’ causeway. I based this conclusion on the fact that this linear body of rock had survived Khufu’s quarrying of the site, which suggests that it was a feature of some importance (consistent with my view that it was part of an early site of solar-worship). Harrell considers that when Khufu was developing the site, his son’s mortuary complex (i.e. Khafre) may well have already been in the planning stage and the alignment of the causeway may have already been established. This argument, however, neglects any consideration of the reign of Djedefre, Khufu’s direct successor, who began the construction of his mortuary complex at Abu Rawash. I consider that the shift in location to Abu Rawash severely weakens any consideration of a ‘masterplan’ for the Giza site.

Schoch dates the excavation of the Sphinx to a period before 5000BC and supports this date by three principal lines of argument:

Although this argument appears persuasive, there are a number of inherent weaknesses and one fundamental flaw: that a pre-5000BC date for the Sphinx does not fit into any known context.

In G:TT, Ian Lawton and Chris Ogilvie-Herald have a chapter titled Context is King. For a site such as Giza, in which there is strong evidence for Fourth Dynasty activity, context is widely used to date an artefact. It is the strength of the context from Giza that has supported the attribution of the Sphinx to Khafre for so long and it is only when hitherto unknown and detailed evidence comes to light, such as the geological evidence described by Schoch and, subsequently, myself does the context begin to weaken.

Having advocated a pre 5000BC date for the excavation of the Sphinx, Schoch has attempted to establish a role or context for his early Sphinx. In search of such a context, Schoch has suggested links with Jericho (from where stone masonry is known, ca. 8000BC) and to stone artefacts from the Nabta Playa in southern Egypt from about 6000BC.

I have investigated these suggested links and have found them both unconvincing. With respect to the possibility of links with Jericho, Michael Baigent in his book Ancient Traces¹⁶ links Predynastic pots found at Giza (see also my paper²), to evidence of traders from the Jericho region who had settled in the Late Predynastic town of Maadi, across the Nile valley from Giza. Baigent describes how many of the pottery remains encountered during the archaeological excavation at Maadi, were clearly influenced by Jericho - evidence, he concluded, that people from Jericho had settled in Maadi, bringing with them their knowledge of working masonry and, he implies, building the Sphinx.

Whilst this link is intriguing, it can not be substantiated by archaeological evidence from the site. An important publication on the subject is "Maadi I - the pottery of the PreDynastic Settlement"¹⁷, in which the authors discuss the presence of Palestinian (including Jericho) pots of Chalcolithic age (4000-3000BC). Not only is this date not consistent with the 5000BC date advocated by Schoch for the construction of the Sphinx, the authors note that the Palestinian pots were of a single type and represented only some 3% of the total assemblage. Given the rich variety of forms of Palestinian ware, the firm conclusion reached was that these pots were not imported in their own right, nor were they brought with settlers - their presence in Egypt was simply due to the fact that they were the standard container for a certain class of goods imported from Palestine.

As for the Nabta Playa, well the Sphinx and Sphinx temple actually have very little in common with the stone circle discovered at this site in southern Egypt (dated to approximately 6000BC¹⁸). The scale of the two monuments could not be different, the Sphinx is some 74m long, whereas the Nabta circle is only 4m in diameter. Unlike the Sphinx temple particularly, which consists of carefully quarried, worked and placed masonry, the Nabta circle is built from roughly hewn blocks. A number of large worked stones have also been found buried in the sand at Nabta. Whilst these monoliths show some advanced features of working in stone, they do not represent masonry and can not, therefore, be associated with the Sphinx.

These distant sites (Jericho and Nabta) fail to provide the early context for the Sphinx that Schoch has sought. More to the point, however, is that we do have archaeological evidence from Egypt for the period ca. 5000BC. The capabilities of the culture from this time are well established, however, they do not include the working of stone masonry.

On the recent Internet posting⁸, criticising Chapter 7 of G:TT, and in his recent book "Voices of the Rocks", Schoch has made the point that I have not commented on the geophysical data that he had obtained from within the Sphinx enclosure, nor have I considered the implications of this work on the dating of the Sphinx.

My reason for not addressing the seismic investigations was primarily connected with the value of this form of investigation when used in isolation. Geophysics, provides an immensely useful range of non-destructive tools, however, in all cases these techniques can merely be considered as prospecting tools. It is common for one geophysical technique to show anomalies where no features exist and visa versa. In addition, different results can often be obtained by the same technique if additional factors come into play. Conclusions drawn from geophysical investigation should always be confirmed by intrusive methods. No intrusive investigation has been undertaken by Schoch.

An illustration of the vagaries of geophysical survey is provided by the team from Waseda University in Japan (Yoshimura et al^19&20), who used two advanced geophysical techniques within the Sphinx enclosure: ground penetrating radar (GPR) and microgravity techniques. In their first season, Yoshimura et al used GPR with a frequency of 150MHz and identified two potential cavities in front of the Sphinx. During their second season, however, the same techniques were used but with a reduced frequency of 80MHz: no significant anomalies were encountered at the appropriate locations. It is not possible to be certain which set of geophysical data is to be believed, however, as Yoshimura et al state²⁰ - ‘It was found that the existence of a cavity could not be confirmed without a boring operation’.

In Schoch’s opinion, however, the seismic geophysical surveys undertaken by Dr Thomas Dobecki and himself²¹ confirm his pre-5000BC date for the original construction of the Sphinx. Schoch’s argument can be summarised as follows:

After excavation of the Sphinx, the newly exposed rocks, particularly the floor of the enclosure, began to weather. In his recent criticism of G:TT⁸, Schoch appears to advocate arid, sub-aerial weathering as the main agent of this degradation, dismissing the effect of modern rainfall etc. However, in his earlier papers, particularly the first paper that he co-wrote with Dobecki²¹, a wider range of weathering agents are considered including sub-surface dissolution and karstic development (related to dissolution of the limestone). Schoch considered that if the Sphinx had been carved in one operation, the depth of weathering below the floor of the Sphinx enclosure would be uniform. He argued that the shallower weathering at the rear of the Sphinx, indicated that the excavation at this location had been cut more recently. Zahi Hawass²² has indicated that a number of masonry blocks on the rear of the Sphinx, date from the Fourth Dynasty. Schoch associated this restoration with excavation at the rear of the Sphinx and, on this basis, argued that the more shallow weathering represented a late phase of excavation, limited to the rear of the Sphinx enclosure, which had been undertaken in the Fourth Dynasty. As the weathering elsewhere across the floor of the enclosure is between ‘fifty to 100%’ deeper, Schoch argued that the enclosure had been excavated some 50 to 100% earlier than the Fourth Dynasty - that is about 7000 to 5000BC. In this way, Schoch‘s was able to ‘confirm’ his early date for the Sphinx, which he had initially established on the basis of a known period of rainfall.

It is necessary to question, however, the validity of Schoch’s key assumption: that the results of the seismic geophysics actually represent evidence for weathering rather than some other factor. Schoch’s conclusion, that the seismic survey indicates anomalous shallow weathering at the rear of the Sphinx, is only one possible interpretation of the data. As discussed by Harrell¹¹, there are other equally valid interpretations, including one in particular that may cast some doubt on Schoch’s interpretation.

In his original KMT article⁵ Schoch discusses four seismic lines within the Sphinx enclosure. The line at the rear of the Sphinx (line S3) suggested a depth of weathered limestone in the order of 1.2m. Three further lines (S1, S2 and S4) on the north and south of the Sphinx, parallel to the body and in front of the paws, indicated weathered rock to 1.8 to 2.5m depth. However, the KMT article simplified the original seismic work, omitting any discussion of seismic line S9, which ran across the floor of the Sphinx temple. In their joint paper²¹, Dobecki and Schoch report that S9 indicated weathering to 1.2-1.5m depth. In addition, they state that the depth of weathering indicated by S4 (in front of the Sphinx) approached 4m, not the 2.5m stated by Schoch in KMT. If these depths are plotted on an east-west section through the Sphinx enclosure and Sphinx temple (bearing in mind that the floor of the Sphinx temple is cut three metres lower than the floor of the Sphinx enclosure) the ‘weathered’ depths can be connected by a sub-horizontal line that closely parallels the dip of the strata. Schoch’s ‘weathered zone’ may, therefore, be a function of the structure of the Member I rock - reflecting the bedding of the limestones beneath the Sphinx enclosure.

A series of First and Second Dynasty mudbrick tombs are situated on a limestone ridge at Saqqara, overlooking the Nile Valley. These early tombs, which conventionally are considered to pre-date the Sphinx, show little evidence of degradation by rainfall. Schoch has taken this in support of his pre-5000BC date for the Sphinx, arguing that the rainfall which eroded the early Sphinx had ended by the time the later mudbrick tombs were built.

We know, however, that significant rainfall has been experienced in Egypt and that, in the appropriate hydrological setting, the resultant run-off can lead to considerable destruction. Reisner showed that sometime after its Fourth Dynasty construction, mudbrick elements of Menkaure’s valley temple were damaged by rainfall run-off. I also consider run-off to be a significant agent of degradation at the Sphinx. Unlike the Sphinx and Menkaure’s valley temple, however, the mudbrick tombs at Saqqara were built on an area of high ground and do not lie within any natural catchment. These tombs will not, therefore, have been exposed to any significant run-off.

That the First and Second Dynasty mudbrick tombs at Saqqara do not show any evidence for erosion is, therefore, a function of their hydrological setting rather than their age. Although it is beyond question that these tombs will have been exposed to rainfall, the fact that they are not significantly degraded, as Schoch has pointed out, demonstrates that rainfall itself has not been a significant agent of degradation in Egypt.

Schoch has also suggested that the Sphinx temple and Khafre’s valley temple are also older than generally thought, having reached this conclusion on the basis of the condition of the masonry of the temples. In support of this idea they cited work by Dr. Mark Lehner⁴. Lehner argued that the masonry used to build the Sphinx and Khafre valley temples was quarried from within the Sphinx enclosure. The concept of the Sphinx as a source of building stone for both temples appears, however, to be the result of some confusion.

On p127 of the Complete Pyramids²³, Lehner uses the word ‘probably’ when discussing the Sphinx enclosure as the source of the masonry for Khafre’s valley temple. In an article in Archaeology²⁴, Lehner is even more circumspect (p33) "..Khafre Valley Temple [was built] from huge blocks of limestone…..that were quarried from the upper layers of rock corresponding to those of the Sphinx head and possibly higher". I also draw your attention to the figure at the top of p207 of the Complete Pyramids. The caption quite clearly states that "Monoliths for Khafre’s temples were channelled out of a quarry southwest of the Sphinx".

If there is a lack of clarity on this issue, it is possibly because of a working hypothesis Lehner developed during the original ARCE Sphinx Project. Lehner postulated that Khafre’s valley temple had been constructed from the Member I rock quarried to form the platform for the Sphinx temple and then the Sphinx temple had been built from Member II rocks quarried from round the Sphinx.

When Lehner tasked a geologist with confirming this, that geologist - Thomas Aigner - was unable to do so. "A typology of core blocks was established on the basis of lithological and paleontological features. The attempt was then made to trace the individual and/or broad types of blocks to the geological stratification and to the horizontal distribution of the facies within given units. In general the study confirmed an earlier hypothesis that the core blocks of the Sphinx Temple derive from the quarry immediately to the west from which the Sphinx was formed. The earlier suggestion that the blocks of the Khafre Valley Temple were taken from the cut into the Member I which created the lower terrace of the Sphinx complex was definitely nullified by Aigner’s study."²⁵

So, whilst it has been proven that the masonry used for the construction of the Sphinx temple was quarried from within the Sphinx enclosure (indicating that the Sphinx and associated temple are of the same age) the source of masonry for the valley temple is by no means proven. It can not be stated, therefore, that Khafre’s valley temple is contemporaneous with the Sphinx.

As discussed above, I attribute the construction of the Sphinx and associated structures to a time when, on the basis of archaeological evidence, the inhabitants of Ancient Egypt had established the skills of working stone masonry - tentatively, the second half of the Early Dynastic Period. This limits the period of time available for the development of the more intense degradation of the Sphinx enclosure to a few centuries rather than the millennia available under Schoch’s dating. Neither, Schoch nor Billington (who by his own admission, is not a geologist) consider that my dating allows sufficient time.

In the preceding sections of this paper, a number of issues have been explored and conclusions drawn. It is probably worth reviewing these issues with respect to the age of the Sphinx:

Can run-off discharging into the western Sphinx enclosure during the latter half of the Early Dynastic Period account for the degradation that is present? I touched on this matter in the 1999 revision of my paper² and argue that, on a face exposed to Gauri’s processes of chemical weathering and exfoliation, soluble salts will first be drawn towards the surface of the rock and will then be exposed to leaching and abrasion once exfoliation has occurred. As weathering progresses, soluble salts are removed from increasing depth, leaving an increasingly insoluble matrix near the surface. This process can, therefore, be seen to be somewhat self-limiting and it is only when a chemically weathered face is subject to erosion - such as from rainfall runoff - will the insoluble veneer be abraded off, exposing salt-rich rocks from the sub-surface. These newly exposed rocks will, once again, begin to rapidly weather and so the cycle repeats.