La Times reported in 1991: Sphinx's New Riddle--Is It Older Than Experts Say? : Archeology: Geologists cite study of weathering patterns. But Egyptologists say findings can't be right.
Since then Robert Schoch, one of the geologists who led this investigation, has made a documentary with the guy who first noticed this (after reading about the water erosion patterns observation in an even earlier observer) John Anthony West. So here it is, the documentary in full followed by an outline of the theory using public domain pictures from Wikipedia. For more detailed analysis watch the video and read Robert Schock's write up on this here.
Mystery Of The Sphinx: This program presents geological evidence that the world's most famous monument, The Great Sphinx of Egypt, may be thousands of years older than we have been taught.
Outline of the basic theory;
One of the biggest discoveries of modern science and Egyptology seems to have come from a bunch of geologists inspired by a man named John Anthony West who noticed rain erosion patterns on the Sphinx. This is unusual because the Sahara, where Egypt is, is a very arid region with little to no rainfall. Thus the problem becomes... either throw all the decades of geological knowledge out the window OR accept that the Sphinx could ONLY have been built when there was enough rainfall to have cause the water erosion patterns caused by rain, that can clearly be seen on the Sphinx by all trained geologists.
Erosion is a well defined and documented process for geologists. It’s something so well known that not even one geologists will disagree with the basic observations of erosion from any other - sane - geologist because these facts are too well known to mess up. Alot of geology is easy to explain as it's a science and uses observation and testing of hypothesis over years. Here is a walk through with the help of images from WIkipedia;
This is an example of one type of water erosion (it cuts THROUGH rock creating a channel)
Here is an example of water erosion through a regular pattern over many centuries going back to the age of the glaciers;
A more extreme example of rain erosion and how it cuts through the rock in channels;
With wind erosion the rock is worn smooth, hollowing out soft layers of rock. Since the wind carries the sand and other elements and it strikes the rock parallel to the ground, wind erosion doesn’t have the up down type of erosion common to water and thus rainfall.
Here is one of the most famous examples of wind erosion and the type of erosion it causes;
An example of standard wind erosion with a little water erosion visible on the extreme left;
Here is an extreme example of Wind erosion pattern of chiseling from the side carving out the soft rock;
The Sphinx is carved from a simple piece of limestone jutting out of the bedrock.
Back of the Sphinx
Moving in closer you can easily see the water erosion patterns as explained above;
A closer look at the left part of the image;
A closer look at the right side of the image;
Let's go over the evidence from another angle.
Here is the front of the Sphinx;
A close up reveals the same water erosion through rain patterns;
Compare the body with the head;
Another view of the Sphinx;
Here is a side view of the Sphinx (notice how the head is smaller than expected given the size of the body and the tail indicating it’s a lion… could the head have been carved into human shape later while earlier it was a lion as suggested in the documentary above?);
In any case, most of the time the Sphinx has been covered in sand as that is the natural way of the desert which means that NO erosion was taking place as the Sphinx was protected by the sand (which further explains why there is so little wind erosion placing the sphinx construction BEFORE the Sahara desert).
Here is a picture from the Brooklyn Museum before the Sphinx was uncovered;
A drawing from 1755 showing the Sphinx how it looked back then (notice the body is covered in sand);
The Sphinx in 1871;
Sphinx in 1878;
As the Geologist, Robert M.Schoch, outlines in an article he posted on his website;
Read the whole article here.
Note: The Sphinx Was Probably Originally A Lion
What I found most interesting is that the Sphinx seems to have been originally sculpted into a lion and then re-sculpted by a later civilization (the Pharaonic one) AFTER water and time had weathered the structure to such a degree that many of the lions head features were probably already gone.
Other Sphinxs of the Egyptian civilization were properly proportioned...
....as was the art of the prehistoric cultures surrounding that area and the Megaliths which seemed to have surrounded it as well. Saying the Egyptians ran out of rock is silly because they could have just made the whole structure smaller and kept it's proportions. In summary, the geological, historical, art and megalith culture evidence all align together to support the theory that the Sphinx had originally been carved out as a large lion.
Update! - 3/302017: Debunking Egyptologists Dr. Mark Lehner From the University Of Chicago & James F. Romano, Curator At The Brooklyn Museum