Most Egyptologists, dating the building of the Sphinx to Khafra's reign (2520–2492 BC), do not accept the water erosion theory. Alternative explanations for the evidence of weathering, from Aeolian processes and acid rain to exfoliation, haloclasty, thermal expansion, and even the poor quality limestone of the Sphinx, have been put forward by Egyptologists and geologists, including Mark Lehner,[19] James A. Harrell of the University of Toledo,[28] Lal Gauri, John J. Sinai and Jayanta K. Bandyopadhyay,[29] Alex Bordeau,[30] and Lambert Dolphin, a former senior research physicist at SRI International.[31]
The chief proponents of the water erosion theory have rejected these alternative explanations. Reader, for example, points to the tombs dug into the Enclosure walls during Dynasty XXVI (c. 600 BC), and notes that the entrances of the tombs have weathered so lightly that original chisel marks are still clearly visible. He points out that if the weathering on the Enclosure walls (up to a metre deep in places) had been created by any of the proposed alternative causes of erosion, the tomb entrances would have been weathered much more severely.[32] Similarly, Schoch points out that the alternative explanations do not account for the absence of similar weathering patterns on other rock surfaces in the Giza pyramid complex
). Maybe poor quality limestone was chosen because it is softer and therefore easier to work into such a huge statue.
