Why wasn't the sea water at sea level?

[ppsa]

I hope this is the right forum for this question! I'm hoping surverys can answer this for me:

A while ago I did a dive in cenote Noc-Ac, north of Merida about half way up to Progresso. Around Merida, the elevation of the Yucatan Peninsula is about 5,000 ft. Since elevation varies by no more than about 1 ft per mile on the peninsula, the elevation could not have been much more or less at Noc-Ac from what it is in Merida. (Do I have my facts straight?)

On the surface of Noc-Ac, as is the case in all cenotes, you find fresh water. While in the cenote, I tasted the water in around 40 ft. and it was fresh. But at around 95 ft. I tasted the water again and it was sea water.
Here's my question: If Noc-Ac is thousands of feet above sea level in elevation, how come I found sea water just 95 ft. below the surface?

Thank you

[skip]

i have no idea why you found salt water above sea level. but there are salt mounds/mountains in the gulf, salt deposits in dryland mountains thousands of feet of above sea level. so it's possible it's not sea water, just salty water!

-skip

[caverkevin]

Altitude for the airport in Merida is 39 feet. It's not that far above sea level.

[Kirk]

Yeah, Merida certainly isn’t 5000 feet above sea level. I doubt it is more than 50 feet. The Yucatan’s topography is a lot like much of Florida; essentially it is a giant sandbar. Last time I drove from Merida to Tulum (granted this was 20 years ago, though I doubt much has changed with inland Yucatan), the road was so straight (meaning no hills, or changes in elevation), that I fell half asleep, and I stopped when the Caribbean was lapping over the hood of the old (even at that time) Plymouth Volare station wagon. Ended up backing it up on the beach before I got good and stuck. Took me four days living in paradise before I got up the motivation to dig it out, and drive back to Minneapolis (via Belize and Guatemala). Wish I knew about cave diving back then. - Kirk

[Squirrel Girl]

When I first read the OP, I was confused. I've never been to Merida, but was shocked to read it was so high! I googled it. Sure enough, 5,249 ft (hah, but then upon closer inspection that was Merida, Venezuela!).

I'm sure you're looking at some variation on the Ghyben-Herzberg lens. You're not on an island, but I'm sure there's similar phenomenology happening. FW (fresh water, not Forrest) is less dense than SW, so it floats. For every 1' above SL the ground water is, there's 40' of FW below SL.

http://www.emwis-mt.org/documentatio...n-Herzberg.htm

[Jay]

What depth did you pass the halocline?

[Webmaster]

You're not on an island, but I'm sure there's similar phenomenology

The study of stuff that happens?

That sounds like a Ricky Bobby term to me.

[rchrds]

Obviously you've seen your answer by now. The area between Merida/Progresso is between 20-30 feet above MSL (mean sea level) (omitting all the errors possible in actually coming to an exact figure) The surface of the salt water makes a curve, sloping downward the further you are from the coast, as fresh water sits above it. So finding salt water 95 feet below sea level (and that is probably not correct either, as the fresh water surface is above MSL as well as you move away from the coast) is not strange at all.

Jason

[Squirrel Girl]

Quote:

You're not on an island, but I'm sure there's similar phenomenology

The study of stuff that happens?

That sounds like a Ricky Bobby term to me.

Really? I don't deny I run in odd circles, but it's a pretty common term, as far as I'm concerned.

One time, I used the term "ubiquitous" at the start of a meeting and no one in the room had ever heard the word. U what?

Do I make up for my geekhood by having watched Talladega Nights for the second time a month or two ago????

[BabyDuck]

only if you pray real hard to precious little infant baby jesus.