Thank you for the opportunity to address the ongoing debate about the age of the Sphinx. I have assumed throughout my presentation that most readers are aware of the alternatives, which have been presented regarding this fascinating topic. As a result, I may have glossed over some of the details, but am certainly willing to elaborate if asked.
To preface, I am not an Egyptologist and have never been to Egypt. I am a geoarchaeologist who has worked in the western United States since 1973.My professional task is to establish the geological setting of the vast array of sites which occur in my area of responsibility. I have worked at sites along the Pacific coast, the temperate rainforests of the Olympic Peninsula, the Columbia Plateau, and, perhaps most pertinent to the discussion at hand – the Basin and Range Physiographic Province which includes mid-latitude deserts similar to those found in Egypt (Nevada, SE California and SE Oregon). So, in a sense, I’m familiar with the environment, if not the archaeology of the Sphinx. Perhaps my independence from the “great” personalities involved in debates about the Sphinx could also be viewed as an asset – I’m not going to lose my job, my funding or access to my study area if I ruffle someone’s professional feathers.
John Anthony West and Robert Schoch first sparked my interest in this topic in the program Mystery of the Sphinx. I was, like many, mildly surprised that someone with Schoch’s credentials would be willing to share the stage with West. However, as the result of his participation, I did not dismiss that portion of the program out of hand. I watched with interest as he dismantled the only alternative hypothesis he chose to present (wind erosion). This, of course, is a straw man argument (maybe, see below). Everyone familiar with desert environments knows that windblown sand is only an effective agent of erosion a few feet, at most,above the ground. Saltating grains of sand, even in the strongest winds, just don’t get much higher than that. So, by eliminating a very weak hypothesis, Schoch concludes the only other possible alternative is running water. He then states bluntly there is little running water at Giza and hasn’t been for the last 5000 years. At that point, I choked a bit. Unless we’re talking Antarctica, there are few deserts on Earth where high intensity thunderstorms are rare. I held my tongue (for my wife’s sake) and expected him to elaborate. But, much to my chagrin, he essentially stopped there. Of course, West then came forward to contradict his expert witness by exaggerating Schoch’s age by a factor of 2 (as we know, this is perfectly acceptable in the world of alternative science).
Over the next couple of years, I noticed other geologists had taken up this problem and presented credible alternatives to Schoch’s running water hypothesis. The most convincing of these was K.L. Gauri’s (1995) argument that the key culprit was salt crystal stress induced exfoliation (SCrySIE).
On reading this paper’s abstract, it occurred to me that the weathering pattern on the Sphinx and it’s enclosure looks very little like that caused by running water, it looks more like what’s called spherical weathering. This process is driven primarily by chemical processes and, basically, turns cubes into spheres (thus, the name). Any object (in this case limestone), exposed to the environment, will be attacked most rapidly at those points which are most exposed, that is, on the corners. As the corners weather, the object presents a smaller and smaller surface area to the erosive environment until, in an ideal world, it achieves the minimal surface area it can present – that of a perfect sphere. I recalled the shape of the stones Schoch had been leaning on in the rear of the Sphinx enclosure – what did they all have in common – they were all nicely rounded – in fact, nearly spherical on their expposed face.
In my mind, this was the end of the debate. No serious archaeologist, geologist, or layperson would support Schoch’s position. My confidence was premature. Along came Colin Reader’s Khufu Knew the Sphinx which I first read on the “Giza: The Truth” website. However, much to Colin’s credit, his argument is better constructed than Schoch’s. Colin explains that the greater degredation of the west wall and western parts of the south wall of the enclosure were the result of runoff from the Plateau west of the Sphinx BEFORE Khufu’s pyramid was built. He then posits that excavation of the quarries used to build the Great Pyramid intercepted this runoff, thus slowing the rate of erosion in the Sphinx enclosure. He goes on to develop the argument that the Sphinx was part of a pre- or early dynastic Solar Cult – perhaps the first megalithic structure in Egypt. According to Colin, later structures at Giza were, in essence, built around this statue. Of course, this does not really support Schoch’s idea. Colin only pushes the Sphinx’s age back a few hundred years, not the thousands of either Schoch or West.
After I “met” Colin on the Amun egroup in the Fall of 2000, he and I engaged in a lively exchange about his ideas and “my” alternatives. Mr. Reader is a true gentleman and an excellent scholar. He has the expertise and the experience at Giza to make valid observations. His interpretations should not be taken lightly.
Colin and I agreed to a few preconditions in the early part of our debate.Perhaps the most important was our choice to exclude the body of the Sphinx from our discussion. We agreed that all of the attempts to stabilize the beast over the last 4500 years may have had effects for which we cannot control. Placing any kind of artificial covering on the body may have hastened or slowed the rate of weathering. Painting the limestone may also have affected the processes acting on it. However, several thoughts about the Sphinx’s condition have occurred to me since our debate which I will present below. Of course, Colin is free to respond to these observations. Toward the end of our debate, Colin threw what he called a “thermonuclear hand grenade.” He sent me a .jpg of the north wall, west of the Sphinx temple where the limestone is much more degraded than that which was quarried during the IV Dynasty beside the Sphinx Temple (the east portion of the north wall). I have not directly challenged his interpretation of that observation as yet, but will below.
Essentially, I am convinced that weathering of the Sphinx and its enclosureare due primarily to the effects of aspect and length of exposure. Running water is a minor player – and here’s why.
To reiterate, the walls of the enclosure under discussion are the west wall (east facing) and the south wall (nearly north facing). Colin correctly observed that the west wall and the western portion of the south wall are more degraded than the eastern part of the south wall and wondered why. He presented the idea that when there were no quarries west of the Sphinx,then a large rain water catchment area would have allowed any sheetwash generated there to reach these walls. When this sheetwash poured over the enclosure walls it would strip off any loose material, exposing newlimestone to chemical weathering (including SCrySIE) and thereforeincreasethe rate of erosion on any wall or portion of a wall it could reach. He sees a change in the rate of erosion near what’s called the “Great Fissure” in the south wall (this fissure extends through the body of the Sphinx as well). He posits that this fissure intercepted the sheet wash – preventing it from reaching the eastern part of the south wall – which is why it’s less degraded.
Superficially, this looks like an excellent idea. It explains why there are differences in degree of weathering at different places within the Sphinx enclosure. But it ignores some basic facts about running water -the most important is its tendency to quickly form channels, not flow as sheetwash for any significant distance (if you doubt this, take a sheet of glass, tip it slightly and spray it with water – it forms into nicely meandering streams). This is particularly true at Giza, where the surface of the limestone is in a state which Colin characterizes as “incipient karstic.” Karst topography occurs where ground- and rainwater dissolves limestone – eventually creating valleys, sinkholes and caverns. At Giza, solution of the limestone has only progressed to the point where joints in the Mokattam limestones are slightly open, leaving the distinctive “blocks” you can see in the walls of the Sphinx enclosure. There is no reason why these open joints, under Colin’s hypothesis of an uninterrupted limestone edifice, would not have extended to the surface of the Plateau before any development at Giza. They would have quickly intercepted any sheetwash and channelized it. I suspect under these conditions the only sheetwash atGiza would be off the surface of each of these blocks and into theirsurrounding joints and thus to the groundwater. So, essentially,Colin’s suggestion that the Great Fissure explains the different degrees of weathering along the south wall undermines his main premise. There are many greater and lesser fissures at Giza, all would intercept sheetwash and insure it never reached the west and south walls en masse – which Colin’s hypothesis requires.
Of course, this whole discussion ignores the fact that much of the time the surface of the Giza Plateau was (and is) covered by sand dunes. But this does nothing to support Colin’s hypothesis. Sand dunes would disrupt the catchment area Colin describes, and channelize the water between the dunes,probably trapping it between dunes before it could flow anywhere.
The final piece in this part of the puzzle is the Sphinx itself. Schoch’s right, it is as severally weathered as any wall in the enclosure, and nothing in Colin’s hypothesis explains why this is the case. No reasonable amount of water originating from the Plateau could have affected the upper body of the Sphinx. But both chemical and thermal weathering could have. My reasoning for setting the Sphinx aside originally still stands – it has been messed with by many different people and is not as clean a lab as the enclosure walls, but any hypothesis regarding weathering must account for its condition as well.
In science, it is one thing to dismantle an idea, it is quite another to come up with an alternative hypothesis which better explains the facts. When I first got into this discussion, I tossed out a lot of hair-brained schemes which Colin quickly dispatched, however, there is one straightforward observation which he has never explained away to my satisfaction – the simple fact the west wall faces east and the southwall doesn’t. To this I can now add another observation based on historic photographs of the Sphinx and its enclosure recently posted to the Amun egroups site and pointed out frequently in past discussions about the Sphinx – it’s spent much of its existence partially buried in sand (partially being the operative word).
The Solar Hypothesis was developed to explain the differences between the south and the west walls. Although we don’t have any numbers with which to quantify the differences, it’s pretty obvious the west wall is in worse condition than the south wall. The solar idea doesn’t take a lot of imagination – just think about what happens when the sun comes up at Giza. On clear days, even during winter, the west wall is immediately exposed to a rapid change in temperature and a concomitant rapid change inhumidity. The Mokattam limestones are made up of muddy limestone fragments, sand and fragments of the creatures whose skeletons formed the limestone. The important point being that there is significant variability between the albidoes of these various particles – some are light colored, others are dark colored. The darker particles heat up more rapidly than the lighter ones – and they expand. This sets up stresses between the light particles nd the dark ones – this stress can be relieved by deformation or fracture.In the case of fracture, micro-cracks open between the particles. When the sun goes down, the particles shrink and fall away from each other. Also, the surface of the rock heats more rapidly than the interior – again setting up stresses which often results in what’s called spherical exfoliation.
And remember that rapid change in humidity? It influences how fast and how often salt crystal stress induced exfoliation will occur. On the west wall, heat from direct sunlight would very rapidly drive off any moisture that had condensed during the night, causing any salts dissolved by the moisture to precipitate rapidly. Again, rapid change means rapid adjustment, making fracturing, rather than deformation, more likely. It is not surprising why the west wall is in very poor condition – it takes the brunt of the sun’s rays when it’s most vulnerable, when it’s relatively cold and wet.
But, what about the west end of the south wall? I think Colin is correct when he states this portion of the wall is more the worse for wear. And here things are not quite so straightforward and involve a bit more speculation. However, I can certainly throw out a couple of observations which explain this difference without re-writing the history of the Plateau by placing the Sphinx in the pre-dynastic period.
First, and perhaps foremost, the west end of the south wall is higher than the east end. This is due to the fact the entire Plateau dips to the east southeast. From the photographs, it appears the west end is at least a couple of meters higher. What does that imply? It’s more “in the weather”and therefore will automatically experience more rapid weathering. Also,in an idealized world, each time the enclosure filled with sand, the eas tend of the south wall would be completely buried first – protecting it from weathering (Harrell’s “wet sand” hypothesis aside). The west end of the wall would be buried later – perhaps much later – perhaps not at all. But it isn’t an ideal world. We know there were two structures near the east end of the exposure – Khafre’s mortuary temple and the Sphinx Temple. Sand blowing into the enclosure may have banked against these structures, burying the south wall progressively from east to west. This same idea may explain the differences Colin noted along the north wall – the east end was buried by sand sooner (not to mention protected by the Sphinx Temple itself) and the west end was buried later, or not at all.
Finally, remember Schoch’s straw man? I invite you to look at the historic photographs at Amun. Over just a few decades, the pattern of sand burying the Sphinx changed notably. Under these conditions, the “zone of influence” of wind blown sand grains would have migrated up and down the Sphinx’s body – probably contributing to its overall degradation. But the head, inarguably the rock in the best condition of all, would never have been affected by this process. Its preservation may, in part, be due to it’s elevation above the zone where wind blown sand is an erosive agent. Before someone catches my apparent inconsistency (the western south wall is higher and therefore more weathered), let me catch it first. I’m only talking about the possible effects of wind blown sand. The main reason the head is in better condition is because it’s better limestone (MemberIII).
To sum up: the weathering seen on the Sphinx and it’s enclosure do not resemble that caused by running water, there are no dominant channels such an idea implies. It is apparent that spherical weathering of the exposed limestone , caused by variations in temperature and humidity coupled with CrySIE, best explains what we see at the Sphinx – on the body itself and along the enclosure walls. Schoch’s and Reader’s assumption that conditions have changed dramatically since the time of the Sphinx’s construction are not necessary to explain its current condition, and should be rejected.