The Dive Evangelist

OK, kiddies. Polina has had a chance to take some bang-up pictures of what these decorations I’ve been going on about look like so the lesson plan is complete. Please open your books to Geology, the page about cave formation. This was our Earth Day dive, so what better way to celebrate than to learn a bit, then go swimming into the heart of the Earth?

Caves form underwater. Having never thought about cave formation beyond the movie version of Journey to the Center of the Earth with James Mason it never occurred to me that this was so absolute. Caves are formed when ground water finds the water table and starts dissolving the minerals in the substrate. Rain saturates the soil and seeps down. As the water seeks a downhill path underground it starts to join and flow as any other trickle builds, eventually, into a river. These subterranean rivers find their way either to the ocean or to topside rivers (which find the ocean) and the water cycle keeps on spinning.

“But Rog,” you say, “When I was a kid my folks brought me to Carlsbad Caverns, and that’s not full of water.”

“Please raise your hand before speaking and give your answer in the form of a question,” I’d say sharply. But you make a good point. What’s more, you’ve hit on the crux of how these caves in the Yucatan are so gorgeous and intriguing. The stalactites and stalagmites I’ve been talking about as thought they’re made out of solid gold chocolate… they need to be not-underwater to form. So at some point the earth managed to keep all the water out of these Mexican caves for the millions of years required. An ice age seems to be a particularly effective solution for keeping lots of water locked up out of the way.

So during the last few ice ages, instead of rainwater seeping through to the substrate and getting flushed away to the sea, it would drip from the ceiling, leaving a little trace of minerals, typically calcite (this will be important later). Those few molecules of mineral left on the ceiling are the start of a stalactite. The few molecules that reach the floor in the corresponding spot become an inchoate stalagmite. With a few exceptions, the tites and the mites form as a pair, eventually joining in the middle to form a column which, once it gets big enough, starts dripping off stalactites of its very own.

The Mexican caves, being so close to sea level, refilled with water after these formations were created and are now diveable. Dry caves happen to be above the ancient water level and are obviously still walkable. Please stay with your tour guide, though. Getting lost in these places is not a joke.

There is a small army of other types of formations and for descriptions on that I’d refer you to the experts. Or to Wikipedia. In any case, I won’t bore you with the details. The most important thing to be learned here is about the calcite. When you come across a largish, rounded topped stalagmite made of this bright, smooth substance and you hold your flashlight lens right up against it… it glows like one of those rocks from Indiana Jones and the Temple of Doom.

And that’s cool. End lesson.

I now refer you to some pretty pictures:
Some stalactites fossilize the shape of a prehistoric waterfall.

A stalactite and its stalagmite just started kissing into a pillar when the water returned.

Go ahead, swim through, there’s more pretty stuff on the other side.

Each level of these stairs was filled with a little, mineral-rich pool of water somehow. I don’t remember how. It’s just real pretty.

Decoration overload.

I am very, very glad I didn’t skip today’s dives. Every once in a while one or the other of my feet will swell up and it hurts like a bastard to walk. As luck would have it, this morning was one of those very mornings it happened. I figured perhaps it would be best to take it easy and heal up so I’d be good to dive the rest of the week without worry.

“Hm,” said Paul.
“What?” I asked.
“Don’t skip today.”
“Oh?”
“No. You can skip tomorrow if you want. But you can’t skip today. Maybe Jim and I can just pull you around the cave so you won’t have to kick.”

Plenty of ibuprofen later I realized why skipping today was not an option. There have been sections of cave in the past few days that have been stunning… today’s dives were stunning from the moment we emptied our BCs to sink to the moment we took our fins off to climb the ladder out. There were more “WOW!” times in just today for me than there were in most of the 1990s combined.

All of the pictures taken above were taken in Grand Cenote today. Those of you who have seen one of Polina’s slide shows know what a talented photographer she is and those pictures are as splendid a demonstration of her skill as any. But as I mentioned before, no picture could ever really do the place proper justice.

Jim and I asked Paul, as we packed our gear, whether in the decades he has spent as a professional underwater cave photographer, videographer, and cinematographer he feels he has ever captured the real feeling of one of these places.

His answer came without pause.

“No. Never.”