<HTML>Elizabeth,
Good question.
Knowing what has worn off would require a reference point... knowing what was there originally... in order to provide the measurements.
Since all the quarry marks, finishing marks, and virtually every other kind of mark is missing from the soft member II layers of the sphinx and its enclosure, it is logically impossible to give an original dimension. Today we still debate how deep the rock was from which the sphinx was originally cut (i.e., how much of the head was originally exposed). It's like trying to guess how big a sand castle was before it got knocked down and the sand washed away.
Now, we do know that the salt exfoliation has been extremely active for a long time. It's a simple process that doesn't require "polution" from modern industry to act as a catalyst or anything like that. It's just water, sunshine and the salts that are in the rock. I recall hearing that every morning, they can sweep out rather large quantities of exfoliated "scales" of limestone that have accumulated from the previous day.
In 1988 a large piece of rock simply fell off the shoulder of the sphinx. It's pretty obvious that rain was not a significant factor in that event.
The debate continues on the original form of the sphinx. The earliest sphinx shape (lion body, human head) was of Khafre's immediate predecessor, Djedefre. (if memory serves). The proportions are not terribly dissimilar to that object, except for the length of the back, which is extended, most likely, to accomodate the fissure that cuts across the "rump" right where it should begin to curve downward. From the front, however, it is reasonably well proportioned, suggesting that little overall stone has been lost... just deep areas where the limestone is significantly softer.
By my (non-geologist) understanding, the softer areas of the bedding in which the sphinx was carved are almost more like a hardened clay than a soft stone.
I'm reminded of another "alternative historian" who has tried to assert that the pyramids are made of a cement-style product called "geopolymers". The theory is riddled with massive theoretical, logical and evidenciary flaws, but there is one element that should be noted. In the NOVA episode, "This Old Pyramid", the geopolymer proponent, Joseph Davidovits, put a piece of the softer limestone from Giza in a plastic bag and let it sit for 24 hours.
<center><img src="[
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<blockquote>After 24 hour soaking in a plastic bag with water, the limestone chunk separated into clay and mummulites. In the presence of an excess of water, the heavier clay settles down leaving the nummulites separated from each other. "This Old Pyramid", WGBH, Boston, 1992 (NOVA, PBS) </blockquote>
From <a href="[
www.geopolymer.org] site</a>. This gives you an idea of how some of the limestone might behave. It is most certainly not all of this soft consistency, but enough of it so that it can create the deep weathering marks we see today.
Given the softness of some strata, it's no wonder the expanding salt crystals can pop off large quantities of the stone. Wind and sand help expose new surfaces every day so that the process can start over again. Add to this an occasional downpour running over the plateau and down the west wall, and you get all the signs we see today.
I hope this helps. All of this is open to correction by anyone with better resources or facts.
Anthony</HTML>
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