cladking wrote

>"If the water was actually saturated with carbon dioxide it would probably have taken
> centuries for it to reach Giza and nearly as many centuries to dissipate."

Water tends to share" it's trapped gas. If you have 500 gallons on H2O with no CO and 500 gallons of water with CO saturation, within a relatively short time period you have 1,000 gallons of water semi-saturated with CO.

It could dissipate immediatly if heat was increased, enough force was applied, or enough pressure was removed. Geologists believe the lake disaster you spoke of occured because the deep water in the lake was shaken by tetonic activity and heated by volcanic activity. The deep water released huge amounts of CO which was liberated at the lakes surface and became a deadly "heavier than air" invisible cloud. It would not explode as dynamite does, but it would fizz off like the coke described below.

CO in water is present as a totally dissolved and absorbed molecule. it is no longer a gas. It will release from it's fluid containment upon the application of force, heat, or lower pressure.

Experiment;
1) Open a bottle of Coke and watch it fizz on the surface and sidewalls.
2) Shake hard with top covered then release containment.

What, in your opinion, would have shaken or heated the groundwater at Giza up enough to offgas? Remember you would need an open chamber to act as the pressure containment and a flooded vent tube to act as the discharge nozzle. (This is how Old Faithful works but it works on heat, not released gases).

Jammer

This explains clearly the cycle of CO;
[scifun.chem.wisc.edu]