The Age of the Sphinx? Colin Reader vs. Robert Schoch – Water Erosion?

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I basically grew up believing the theory proposed by Robert Schoch and John Anthony West in 1992 that the Sphinx was eroded by water and, as the story goes, the only time that could have happened was about 5000-7000 BC. ((Schoch, Robert M. (1992). “Redating the Great Sphinx of Giza”)) which is of course far earlier than the conventional date for the construction of the Sphinx (during the reign of the Pharaoh Khafra c. 2558–2532 BC.) ((Dunford, Jane; Fletcher, Joann; French, Carole (ed., 2007). Egypt: Eyewitness Travel Guide. London: Dorling Kindersley, 2007))

Schoch’s  early date for the Sphinx has been subsequently used by folks like Graham Hancock to support his theory of the existence of ancient civilizations like Atlantis. Others have noted Schoch’s work to promote the idea of  a prehistoric alien visitation and similar ideas. I think such theories are unnecessary in light of the evidence I will present in this article.

Unlike similar debates with ancient alien implications this one has played out in scholarly circles, most of the articles being published in the late 90’s and early 2000’s. For a very thorough, unbiased cataloging of this scholarly debate I would recommend this series of posts from  David P. Billington’s website.

One of the first things I think it is important for anyone that believes Schoch’s model to understand is that this debate is not really about the sphinx itself, but rather it is mostly about the western side of the enclosure wall in which the Sphinx sits. If you do an image search for “water erosion Sphinx” or a similar phrase, you will not typically see close up pictures of the Sphinx itself, instead you will see a lot of pictures of the western enclosure wall, and the western side of the southern enclosure wall.

Colin Reader, a British geologist who was inspired by Schoch’s claims did a study of his own which concluded that the water erosion that was noted by Schoch is not evenly distributed at the site, and he concluded that the western enclosure wall was not eroded by rainfall per se, but rather rainfall run-off (explained below.) Rainfall run-off would explain the extreme water erosion on the western side of the enclosure, and why the same characteristics could not be found either on the other enclosure walls, or on the Sphinx itself. ((Reader, Colin (2002). “Giza Before the Fourth Dynasty”, Journal of the Ancient Chronology Forum

The Giza Plateau has an eastward sloping topography which causes a natural rainwater run-off into the west part of the Sphinx enclosure which would erode the limestone along the exposed western enclosure walls and selectively exploit any joints exposed along the cut face. This view is contrasted with Schoch’s initial assertions which stressed that direct rain was the cause of the erosion of the Sphinx enclosure, not rain run-off such as Reader proposed.

Reader’s theory was met with more enthusiasm than Schoch’s by mainstream egyptologists, who by this time had realized that they too had better come up with a theory on this anomalous weathering on the enclosure wall. But there was a problem with Reader’s theory as far as they saw it. If Reader was right, it would mean that the the Sphinx was about 400 years older than they thought, and even though Reader’s date was 3000 to 5000 years after Schoch’s  it was still not something they were excited about agreeing to, though at present they have settled on a type of stalemate, calling Readers theory “possible” but not “proven.” ((A. J. Shortland, C. J. Doherty, Comments on ‘A Geomorphological Study of the Giza Necropolis, with Implications for the Development of the Site’

The reasons that Colin Reader proposed that Khafre didnt build the Sphinx often were the same ones that Schoch was using with a few notable differences. Primarily because if the erosion was caused by the water drainage coming into the enclosure, then the Sphinx would have had to have been built before the quarries which lay to the west. This is because the natural path that the water would have taken on the way to the western enclosure wall would have been forever interrupted when the large quarries were made.

In addition Reader proposes that the Sphinx was carved by an early solar cult on the plateau, which is why the Sphinx is facing toward the rising sun. He also proposes that it likely once had the head of lion and not a man, but that the head was carved down to look like the head of Khafre during the time that the Sphinx was integrated into Khafre’s memorial complex, which may explain the current disproportionately small head in relation to the bigger body. It seems that Schoch is endorsing this lion view on his website too.

In many ways this debate comes down to rainfall, when was it happening at Giza, and how much of it was there? As I have already stated Schoch’s model emphasized that rainfall, not rain run-off was responsible for the deep erosion on the western enclosure wall, and therefore Schoch needs a lot of rainfall, and a lot of time to make his theory workable. Whereas Reader’s theory, since it proposes that the collected water from the plateau gathered together and drained at the western enclosure wall, he needs a substantially less amount of rainfall and time to account for the erosion of the limestone wall.

So lets talk about rain. Despite what a lot of the websites and documentaries that talk about Schoch’s theory try to make you believe, the increased period of rainfall that Schoch always sites did not just end abruptly 10,000 years ago. I will quote from Reader’s article published in the journal Archaeometry called “A Geomorphological Study of the Giza Necropolis, with Implications for the Development of the Site:”

“The rainy conditions of c. 5000±7000 BC, to which Schoch attributed the degradation of the Sphinx, will have been separated from these later arid conditions by a transitional phase, during which increasingly arid conditions will have been interrupted by occasional, probably seasonal rains. Flood damage to Menkaure’s valley temple (Reisner 1931) attests to the fact that, even during the late Old Kingdom, rainfall run-off was a significant agent of erosion at Giza.” ((

In other words there is more than enough rain to cause the erosion during the time that Reader is proposing for the Sphinx, especially when you consider that Reader’s theory needs only a tiny fraction of the rainfall that Schoch’s theory needs. But again this transitional period between 7000 BC and 2350 BC had plenty of rain, and even short bursts of rain which would cause the kind of flash flooding that could cause very quick erosion, Reader sites other examples of this on the Giza plateau in the excerpt above.

Though Schoch has not written anything new in the scholarly journals about this, he did briefly interact with Reader’s points in a point counter-point which I have put together, and will post at the end of the article. Also in an interesting twist, in a June 2005 interview Schoch endorses Reader’s theory about the water run-off and the quarries, but says he doesn’t think that even with run-off being the primary agent of erosion, it would be enough water to cause the erosion seen on the western enclosure wall, obviously implying that he still thinks it needs the increased rainfall of his much earlier period. Though his reasons for this belief are not clear, he offered that though he agrees that the limestone is of poor quality on the wall, suggesting it could be eroded easily, it is not as bad a some writers suggest. (( This interview with Robert Schoch originally appeared in Issue 1 of our free online magazine SUB ROSA June 2005))”

As far as I am aware Schoch has never interacted with Readers’s responses to his criticisms ( which are listed below), nor has he explained why he thinks the limestone rocks would need more time or more water than what there was during Reader’s earlier date. He does however make points regarding the context of the site, and his own subsurface findings which are discussed at length below.

To be sure there are other types of erosion, besides water run-off going on at the Sphinx enclosure and on the Sphinx itself, but almost all parties agree more or less on the basics of the others these days, even the mainstream guys.

The Sphinx is made up of three different types of limestone, each with different strengths. The top and the bottom parts are much stronger than the middle part which makes up most of the body of the Sphinx, and is badly eroded by a number of factors. As I said almost all parties agree, including Schoch and Reader, that the erosion seen on the Sphinx itself is caused by a number of factors including rainfall (not run-off.) Even the conventional date for the Sphinx allows for a couple hundred years of light rainfall. (( K. Butzer: Environment and Archaeology: An Ecological Approach to Prehistory (Chicago, 1971) ‘… extensive sheet washing – in the wake of sporadic but heavy and protracted rains – are indicated c. 4000-3000 BC. Historical and archaeological documents suggest that the desert wadi vegetation of northern and eastern Egypt was more abundant as late as 2350 BC, when the prevailing aridity was established.’ )) In addition all parties now agree that salt exfoliation, or “chemical weathering” proposed by K. Lal Gauri also is playing, and has in the past played a major role in the erosion of the Sphinx. Here is a description from Colin Reader about this process which can, and does happen even in the desert conditions today:

“Dew, forming at night on the exposed limestone, removes soluble salts from the surface of the rock. Capillary forces draw this solution into the pores of the limestone matrix, where further salts are dissolved from the internal pore walls. As daytime temperatures rise, the solution begins to evaporate, precipitating salt crystals within the confined neck of the pores. The pressure which the crystals exert as they grow, leads to flaking of thin rock layers from the surface of the limestone.”

Schoch has another line of evidence which centers on what Schoch believes to be subsurface weathering of the floor of the Sphinx enclosure. He attained this data from non invasive seismic geophysical surveys. This part is a bit technical for me but it was explained to me this way by someone involved in this debate who wished to remain anonymous:

“What Schoch tried to do was date the exposure of the enclosure floor to dry-air weathering. When rock is exposed to the atmosphere, it begins to undergo chemical changes and the depth of this change or weathering can be a measure of how long the rock has been exposed. What Schoch did was measure the depth of weathered rock using sound waves (these bounce back very fast if the rock is sound and more slowly if it has weathered). He found that the rock under the floor, along the sides and front of the monument, had weathering that was twice as deep as the rock under the passage in back of the monument. From these findings, he concluded that if the back passage was excavated by Khafra, then the main body of the Sphinx would have stood on an exposed floor beginning sometime between 4750 and 7000 BCE.”

Colin Reader’s response to this is typical of the other geologists that have reviewed Schoch’s claims in this regard.

“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 al19&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.”

To make a long story short, if Schoch is right about this subsurface weathering, he will need to have cores drilled at the site to prove it, as it will be assumed to be the sloping natural bedding otherwise. Regrettably, the Egyptians drilled below the floor in the 1990s to determine how high the water table had risen but they did not preserve any samples of the subsurface rock. A sample may be possible to take if somebody remembers to do so the next time there is drilling to monitor the water table.

In conclusion, I think that the following points are persuasive:

  • The very selective severe weathering, on the western side of the enclosure wall, and not on the other sides of the enclosure, or on the Sphinx itself are very positive signs for Reader’s theory being true, especially considering the positive evidence for the Sphinx enclosure being a natural drainage for the plateau.
  • The rainfall during Reader’s revised construction date (400 years earlier than the mainstream view, but 2500-5000 years later than Schoch’s) was more than enough to produce the erosion seen at the Sphinx site. The rainfall tapered off over thousands of years, it did not abruptly end.
  • The other aspects of this debate, such as the context and the other buildings around the area are in Reader’s favor which can be understood by reading some of the articles below.

See the links section below for more reading, this issue requires more reading if you want to be fully informed on it.

Also check out Reader’s responses to Schoch below, as far as I know there has been no further public interactions after that point.


Reader’s response to Schoch’s criticims

Schoch: 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 precipitation-induced erosion seen in the Sphinx enclosure was produced in only a few centuries.

Reader: 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: 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 3100-3000 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: 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.