Passage size - Phreatic vs Vadose

[Rob]

Digging this one back up again in case ayone has any more examples...

Pitlamp, thanks for the Ingleborough Cave example. Had a look at some surveys, seems feasible, although unfortunately quite a complex area, especially with Lake Pluto and Lake Avernos seemingly on a fault that may have created the enlargening, as with East Canal. Although i've never been there so i'm dependant upon you're knowledge of the system really.

ian.p, sorry i think i disagree again. A passage is only phreatic because the floor level somewhere downstream is higher than it. No other changes necessarily need to occur. Therefore there may well exist a relatively "clean" example that proves it can happen.

 

[graham]

ian.p, sorry i think i disagree again. A passage is only phreatic because the floor level somewhere downstream is higher than it. No other changes necessarily need to occur. Therefore there may well exist a relatively "clean" example that proves it can happen.

You miss Ian's point which that there will be an external cause for the change in floor level that you describe.

 

[Rob]

Downstream yes, but not necessarily in the zone around the change between vadose and phreatic development.

 

[graham]

Downstream yes, but not necessarily in the zone around the change between vadose and phreatic development.

A pint says that you cannot find a clear example of a vadose/phreatic phase change that does not have an external cause, usually geological or base-level.

 

[Rob]

And 1700 views show to me that there's very few examples of phreatic sections being larger than their vadose counterpart.

 

[Fulk]

Rob, if I understand correctly what you mean by

And 1700 views show to me that there's very few examples of phreatic sections being larger than their vadose counterpart.

, here are a couple of samples; I'm sure there must be (many?) others ? the 'classic' phreatic passages in Peak cavern and Ibbeth Peril Cave, where nearly-purely phreatic passage have hardly been modified at all by the vadose streams running on their floors.

 

[Rob]

Unfortunately you've not understood. The first few posts explain better...

 

[Fulk]

:-[ Right, I see, when a vadose stream enters a sump . . . well, I guess I'll have to leave it  to the divers.

 

[TheBitterEnd]

Rob, I expect that your assertion is correct for the vast majority of cases. The "Four state model" of cave development (Ford & Williams - Karst hydrogeology and geomorphology) would seem to lead to the situation you describe where lowering piezometric surface leads to vadose entrenchment of phreatic loops connected to sumped phreatic passage.

As others have pointed out and as one would expect with such a complex and chaotic process, there are exceptions.

 

[Rob]

Oooo, looks like i've just found my new bedtime reading book. Thanks for the link

The case studies i'm interested in don't require dewatering of the phreatic zone, as it's not the vadose entrenching that i'm looking at. Rather a fully vadose passage leading to a fully phreatic passage. That make sense?

Of course dewatering of the phreatic will be required if they going to be observed by non divers...