Agreed. I think Chris was just noting that his understanding of the process has changed, and he was outlining why.

I also agree that there is no need for a pre-dynastic source of flooding. Here's a video of a relatively recent thunderstorm at Giza: [www.youtube.com]

As you mention, Warwick, limestone (especially when high in salt) can erode very quickly.

You can see a fissure exposed in the 4th dynasty tomb of Ka-niswt here:



I took that picture in 2004. It would be interesting to examine the same fissure today. My feeling is that it's relatively young and has since been deepened to appear more rounded like what we see in the Sphinx enclosure.

I wonder what effect strong earthquakes can have on opening new fissures in exposed limestone.