This is part of the Temple in front of Khafre's Pyramid. Please note the pot marking of the stone. I don't think it was weathered by air. The salt in the water, effects the chemistry within the rock, reacting and eroding it in random order. It would need to be underwater for this effect to take place...?
It's kind of strange, that the areas which has cut steps, seem to have not eroded the same. Granite cladding?
Would be great, if we had a Geologist handy, to give us his opinion.