Geologist Robert Schoch claims that the angularity between recessed and protruding layers on the facade of the
Tomb of Debehen indicates that it was eroded by wind. The rounded profile of the Sphinx, he contends, resulted
from water erosion and proves that the sculpture is much older. Archaeologists believe both tomb and Sphinx were
carved during the 4th Dynasty (2575-2134 B.c.). The tomb facade--originally the western side of the Khufu quarry,
459 yards west of the Sphinx and 75 to 141 feet higher--is carved in bedrock higher in the geological sequence of
layers than those of the Sphinx. The different weathering profiles reflect differences ill the physical properties of the
rocks, not the age of the monuments. Schoch and West cite the roundness of the protrusions and recesses in the
south wall of the Sphinx ditch as evidence of rain erosion, and believe that fissures in the rock were caused by
rainwater after the Sphinx was carved. Most scholars believe the fractures were caused by tectonic forces and
eroded by groundwater long before the monument was carved.
--ZAHI HAWASS AND MARK LEHNER
http://guardians.net/hawass/remnants.htm