Pressure Depth in a Cave

[reefnet]

so in a normally occurring air pocket, if you surface into it, your gauge would read zero, right?

Not if the water level in the pocket is below sea level.

Think about it: you ascend to the water/air interface. You slowly raise your arm into the air pocket. Do you think the pressure gauge will instantly drop to zero? It's a good thing that's not how it works or you'd be bent worse than a pretzel in there.

 

[boat sju]

reefnet,

Andy was asking about a "normally" occuring air pocket. If you are at depth and encounter an air pocket it got there by some not so normal means. What we could possibly encounter in recreational diving situations would be regulator exhaust. I wouldn't take a deep breath from any air pocket encountered at depth in a cave or wreck.

 

[reefnet]

Andy was asking about a "normally" occuring air pocket. If you are at depth and encounter an air pocket it got there by some not so normal means.

Not being a cave diver, I must ask: Aren't gas pockets present naturally in deep cave systems? If the ceiling is non-porous and you have gases bubbling up from lower in the crust, it seems possible - even probable.

As for the depth reading, it all comes down to the water level relative to the free water surface at the entrance/exit. Natural air pocket or not.

 

[Dive-aholic]

The gas pockets in caves are created by exhaust bubbles from scuba. I've never seen bubbles coming out of the floor of a cave.

 

[Lightning Fish]

Although the answer has already been given, here it is again, 2 ATA. This is an open system, thus, the pressure is a function of the height of the water column.

If it was closed, then it would be impossible to enter the cave. If you think it is closed, poke a hole in a scuba tank and convince yourself that the tank is still closed.



<<Dang! Note to self: next time read all 154 posts instead of just the first 40>>