THE SPHINX

(1) Precipitation-induced weathering is seen on the body of the Sphinx and in the ditch or hollow in which it is situated. This gives a rolling and undulating vertical profile to the weathered rocks and is very well-developed and prominent within the Sphinx enclosure. The rocks displaying this mode of weathering also often contain prominent vertical crevices and other solution features, as well as cross-cutting diffusion fronts.[6] Many of the vertical and inclined solution features follow joints and faults in the bedrock.

(2) Wind-induced weathering and erosional features are seen on structures that are attributed unambiguously to Old Kingdom times. In this mode of weathering, the original profiles of the carved faces of tombs and other structures are still clearly visible (sometimes containing easily legible hieroglyphic inscriptions); but the softer, less competent layers of rock have been "picked out" by wind and sand abrasion, with the consequent formation of deeply eroded "wind-tunnel" features.

This wind-induced weathering is distinctly different in nature from the precipitation-induced weathering; it is well exemplified on various Old Kingdom tombs and structures south and west of the sphinx, which have been carved from the same sequence of limestones as the body of the great sculpture itself.

(3) Present on the body of the Sphinx, as well as on other Giza Plateau structures (and essentially forming an overlay on many precipitation-induced and wind-induced megascopic weathering features), are weathering features that are interpreted as resulting from relatively recent (within the last couple of centuries) efflorescing of dissolved and recrystallized minerals (such as halite) on the rock surfaces, which have subsequently flaked off and deteriorated the stone.[7]

(4) Weathering due to the dissolution and recrystallization of calcite and other minerals in the rocks is visible within various tombs and other chambers cut into the bedrock of the Giza Plateau. This may occur on a daily basis, as water condenses on the cool surfaces of these man-made caves, and subsequently evaporates once again as the temperature rises. This condensation and evaporation cycle gives the surface of the rock-and any carvings it may bear-almost the appearance of melted wax, at times covered with a very fine coating of mineral crystals. This is the most minor component of weathering observed on the Giza Plateau. It is preserved in only a limited number of artificial cave-like structures, such as tombs directly north of the Sphinx on the eastern edge of the Plateau.