<HTML>Alex, me old mate and sparing partner,
before you get too excited about my aparent conversion to Bourdeauism, please read on....
Hello All,
Thanks for the kind words of welcome, but I want to make it clear that I won’t be stopping long! I’ve enjoyed my involvement with EGYPTNEWS then AMUN but, when it comes to these discussion groups, I feel a bit exposed from viruses and find that as any contribution I can make is limited in scope, after the initial flurry of activity I don’t have that much to contribute. So, thanks to all those who spend so much time running and moderating the discussion sites but my approach from now on is ‘short and sharp’ – get in there, state my case, argue a few points and then disappear quietly……
Alex, was I acerbic? I thought I was being rude – must try harder :-)
Whilst I try to be proper about this and not get too personal, I think Alex knows very well (and indeed plays on the fact ;-) ) that there are two things about the way he conducts this argument that really wind me up:
1. that he focuses on one narrow aspect of the debate and refuses to engage in the wider arguments – case in point, I set out a number of issues in my post last night and he responded to one!!! I’ll come back to this..
2. despite repeating time and time again, Alex still has me advocating weathering clocks – now that really gets the blood boiling!!
Some have decried the geology, stating that it’s not proper science because it allows greatly different interpretations. It is the case that often there’s no right and wrong in geology because the processes that are being debated happened long ago and some of the unequivocal evidence has since been removed – is gone for good. But please, don’t throw the baby out with the bath water – if we could produce a number which gave an unequivocal answer and, indeed a proof, we would not be able to enjoy this debate – the thing would have been resolved years ago. So thank God for the room for manoeuvre the ‘science’ of geology gives us – it means we can enjoy the cut and thrust for a bit longer.
Focussing on the narrow evidence of the degradation of the Sphinx…..it remains my strongly held view that this is the result of erosion by run off, which ended with Khufu’s quarrying of the site and, since then, has been modified by chemical weathering and exfoliation as its proponent, Gauri calls it. Alex sees problems with this and advocates chemical weathering (or ScrySIE as he calls it) as the solution. As we’ve debated time and again though, ScrySIE explains far fewer of the observable degradation feature than the run-off model does.
For example, Alex has claimed that the more intense degradation of the western enclosure wall was the result of aspect – it faced east towards the rising sun and would therefore be expected to be more intensely weathered. But as I’ve pointed out endlessly, the chest of the Sphinx and a whole range of other (IV dyn and other) exposures at Giza also face east. I’ll mention here the tomb of Debehen which is probably, but not yet proven to be, cut into the same Member II strata as the Sphinx.
What is obvious, though, is that the degradation of all these other exposures is nothing like that of the western Sphinx enclosure wall – there’s not even incipient development of the rounded degradation of the Sphinx enclosure. So whilst ScrySIE may work in a narrow context (that of the walls of the Sphinx enclosure) it doesn’t work in a wider context because it does n’t explain ALL the features at Giza.
Alex’s response to this point has been to claim that, maybe, the quality of the rock of the western enclosure walls was different. While that’s not impossible, none of the geologists who’ve studied the rocks have identified such a change in rock quality. You’d imagine that if it WAS there, those that argue for the IV dyn Sphinx would have seized on it as it would certainly provide a ready explanation for the pattern of degradation. So at best this line of Alex’s is supposition and not supported from any quarter.
Therefore, I argue, run-off provides the BEST FIT for the site as a whole and, to boot, it is also consistent with other features that are present – the channel across the floor of the enclosure for example. If you reject run-off, you then have to explain why only the Sphinx and a few other limited exposures have the degradation features that seem to cause so much excitement!
As I argued last night, the evidence is firmly against post-Khufu run-off affecting the Sphinx.
Perhaps contrary to what I said above, there are in fact a small number of exposures that have similar features to the limestones of the Sphinx enclosure. One was mentioned yesterday – the trench leading up to the tomb of Kausert (Porter and Moss). I’ve studied Kausert for other reasons and whilst I did not notice anything particular, I have not yet had chance to study this trench so will reserve judgement – what I am happy with though is that the scale of the features is different from that of the Sphinx – I’ve stood next to that trench and did n’t see anything remarkable!
The only other features on the site that show similar features of degradation to the Sphinx enclosure (the tombs of Khentkawes and Kai) have erosion features on the southern face (not just the eastern) – which ties in with the principal that this erosion is controlled by the local topography – i.e run-off downslope – rather than aspect. Not only is there the evidence of erosion, these tombs bear the remains of Early Dynastic architectural features….so what does that tell you ?
But for me, the degradation of the Sphinx enclosure by run-off, is only the starting point. I then try to move on to the other evidence - the strengths in this greater case are that it has so much corroborative evidence - the argument for Early Dynastic development is supported by other often disregarded evidence (disregarded because it sits uncomfortably with a IV dyn date?) that is available right across the plateau.
For example… the unweathered IV Dyn cutting in the north of the enclosure, unique architectural links between the Sphinx temple and parts of the Khafre mortuary temple, the evidence for pre-IV dyn activity at Giza. The evidence is there, I can support it all by reference to publications by the key Egyptologists that undertook the work and, taken as a whole, this evidence is persuasive. But it’s also at this point that Alex and others decline to engage.
Alex, I thought you’d like that one about the incised channels in the sand backfill of the quarry. Last night I started to draft a paragraph or two to explain why the processes that controlled run-off over the sand backfill are not necessarily the processes that controlled run-off across the limestone plateau – after all, we are talking about different materials (windblown sand and limestone) and very different timescales ( a few hundred years for the Sphinx and a few thousand for the quarry) - but thought I’d leave it be – knew there’d be another time and place.
So, what about Alex’s assertion that I oversimplify the run-off model? What Alex is suggesting here, and forgive me if I’m putting words in your mouth, Alex – it’s unintentional but I’m paraphrasing – is that he does not deny run-off will have been a feature at Giza – but that he feels that, rather than form a large number of poorly defined channels, it will have formed a small number of dominant channels. If this was the case the walls of the Sphinx enclosure, if eroded by run off, would be dominated by a small number of deep erosion features, not a large number of lesser ones.
This development of a mature drainage system is understood - its a fundamental principal of geomorphology but let me elaborate on the point above on timescales: Alex and I have been through this before and I'm not sure I explained myself too clearly, but for those of you who’ve not had the pleasure it is worth picking up again. Note, though that in the true traditions of geology this is not a proof – it’s an interpretation. It is plausible and consistent with what evidence survives so, while I can’t prove this, I don’t believe it can be readily dismissed. It’s not possible to disprove it therefore.
Before the Early Dynastic there was little significant activity at Giza (by significant I mean ‘landscape changing’ – no major quarries or stone buildings) and, over geological time, a mature drainage system will have developed – a small number of deep wadis as Alex suggests. One such wadi existed to the north of the Sphinx.
This status quo was altered in the Early Dynastic when the Sphinx was carved from a low hill that formed the southern bank of this wadi. With that action, the hydrology in the vicinity of the Sphinx was changed for the first time. Where there had been a rise in ground levels and a wadi-bank before there was now a hollow – the Sphinx enclosure. Water discharging along the mature drainage will have been able to discharge into the enclosure. As the cut faces were fresh, there were no mature drainage channels to limit the number of points of discharge and the run-off will have been controlled by the distibution of joints in the limestone – with erosion concentrated along the exposed joints.
Now this situation prevailed for a few hundred years at best – no time for a mature drainage system to develop – than Khufu quarried the site and the hydrology changed again.
For the last 4500 years the quarry behind has filled and developed its own (mature) drainage – as shown on the 1920/30 aerial photo.
So I reject that my model for run-off is simplistic – it recognises and accounts for many of the features on site.
Hope this clears a few points up.
Colin</HTML>
