Cave Geology

[bahamaben]

Hiya Gang,
I didn't know where else to put it, so conservation seemed to fit. Can anybody explain to me the relationship between the 3 great cave areas of Florida(north), Bahamas, and Yucatan? Obviously the common denominator is limestone and Karst landscape. The questions I have relate to how the caves of the Bahamas and the Yucatan are so heavily decorated yet low flow, yet the majority of the Florida caves offer high flow and few decorations. I have my own ideas, yet would be grateful for anyone with documented theories to tell me what really happened.
Cheers, and looking forward to hearing some new stuff.
Ben.

[Cindy]

Hi Ben, I'm not a Geologist but I know that decorated caves were once air filled. That's how the speliothems (formations) were made, slow drip of water over hundreds and thousands of years. The Florida caves for the most part have always been water filled. There are a few that have a decoration or two like Climax cave but they are air and water filled even now. If you look on the website of the NSS www.caves.org there are several books on the subject. Cindy :)

[FW]

Good answer Cindy.

The reason that they were once air filled is because the ocean level was lower during the ice age. Florida is a little higher, so most of its UW caves were always underwater.

[bahamaben]

I suppose that's the crux of my question, if the Florida caves are 'a little higher' (i.e.higher above sea level now), surely they would have stood empty of water for as long or longer as the caves in Mexico and the Bahamas, thus having as good a chance of forming speleothems.
Perhaps the landmass of Florida is rising(due to tectonic action, or 'bounceback' after the removal of the weight of glaciers(isostacy?)), so the caves have been submerged for more time.
Perhaps the higher flow(itself perhaps a result of the higher gradient between the freshwater table and present sea level), has eroded any speleothems which did form.
Perhaps Florida recieved less rainfall during the ice age, reducing the opportunity for limestone to be dissolved in rainfall, and later to be precipitated as speleothems in largely dry cave tunnel.
I am sure there are many other scenarios, or combinations of factors, which could help explain the scarcity of formations in Florida's caves.
I'm not a geologist either, but I'd love to be ponted in the right direction to answer some of these questions.

[curtschu]

I think the difference is not so much in the geology as the Hydrology of the locations. If I remember right Mexico and Bahamas are Lens regions which means the fresh water is floating on salt as sea levels rise and fall so does the water in the cave. Florida is an Aquifer or conduit with High static pressure created by the influx of water from higher elevations upstream and recharge area in and around the various spring basins.
While we percieve No Flow in some systems this really is not true it is just so small we can't feel it but in Hyrological terms it is moving downstream.

You will see that there are some caves very close to the Florida west coast that exibit lens type and aquirfer type of chariteristics Wayne World I believe (correct me Joe).

I say all this with the statement that this is a Laymens understanding (I studied weather not Geology) I could be totally wrong and I did not stay at a Holiday Inn last night

[FW]

Curt has the right idea. I should have mentioned that difference in my first answer.

[bahamaben]

The so called 'no flow' systems of Mexico and the Bahamas are actually the same, the water is moving but virtually imperceptably. If it wasn't, the caves would become stagnant, and visibility would be greatly reduced.
So, has the greater flow from the upstream aquifer been sufficient to keep the caves water filled enough of the time to prevent any significant speleothem development (so called 'keyhole' shaped passages are evidence that the caves have not always been completely filled)?
Or, has the majority of speleothem development been removed through erosion by the prevailing 'high flow' conditions?

[akcaver]

I dont think the speleothems have been removed by erosion, or there would be at least some evidence of having formations in the past. There are a few caves with formations in them, check out this past discussion:

http://cavediver.net/phpbb2/viewtopic.php?p=30544&highlight=#30544

But noone really knows why there arent any speleothems in the florida caves, my guess is that there never were because the caves are deep and have always been flooded. Just my scientific guess though 8)

[FW]

Most Caribbean caves are connected to the ocean. Most UW Florida caves are "isolated" by rivers. The fresh water aquifer in Florida keeps them full most of the time. Occasionly there are bad droughts that allow some air in them, but never for long enough periods for secondary formations.

Sometimes FL caves have collapses, due to lack of water supporting the ceiling. We call that sinkhole formation :-)

Remember there are also "dry" caves in Florida. From what geologists have been able to tell, the aquifer level hasn't changed a whole lot in FL. In the Caribbean, the ocean level has changed upwards of 50', judging by formations that are 40' long.

[Bill Rotella]

And soon with global warming the seas will rise up to 30 feet within the next 50 years.