Cenotes and Dinosaurs

This cenote had the roots of a tree hunting out the fresh water

Natural wells.

That's the closest translation I can find for the Spanish word cenotes. A cenote, then, is a naturally occurring underground aquafer or reservoir. So far so boring. Where it gets interesting is that these water courses can sometimes work their way through the soft and highly permeable bedrock of Mexico's Yucatan peninsula to form large, freshwater cave systems. As the rock is so permeable all the rivers in the Yucatan have burrowed their way away from the surface so that, unless you know where to look, the whole region appears to be devoid of any drinking water; but before I continue with caves I have a slight digression.

The Yucatan peninsula is quite a place, not just historically and culturally as I have begun to explain in my previous post, but geographically and geologically as well. Let me explain via the medium of dinosaurs.

Dinosaurs, for those that have never seen Jurassic Park, are super mega cool giant lizards that mostly went extinct approximately 65 million years ago at the end of what is known as the Cretaceous period. I say mostly as all birds are evolved from dinosaurs. But what caused this extinction? Volcanoes? Meteor impact? Climate change? Disease? Well, the answer is that it was probably a bit of all of these but the single most significant of them has now been shown to be a massive strike from a meteor 10km across. And where did this most monumental of meteors strike the Earth? The Yucatan. You would think that the crater left by such an impact would be huge, and indeed it is, measuring some 180km across, but that doesn't mean that it's easy to see. If you were to wonder along the north coast of the Yucatan you would walk right through it and never know you'd been inside one of the planet's largest scars. It was only discovered in the late '70s and it was many years before it was even established that it was a crater, nevermind the most likely candidate for wiping out the dinosaurs.

These little fellows were abour 6 inches long but kept to themselves

In the years since it's discovery the crater, known as Chicxulub after a nearby town, has given up a wealth of evidence including a layer of impact dust covering the Earth and a gravitational anomaly at the site. You can see a review of this evidence along with several cool pictures here. But what, you ask, does this have to do with today's topic of discussion? Nothing really, I just wanted to write about it. Actually that's not strictly true; if you look at the third image in the link above you'll see dozens of little white dots that rather nicely help demarcate the boundary of the crater. Each of these dots represents a cenote. The two cenotes in my pictures here are on the very right hand edge of the picture just over half way down.

These cenotes were the lifeblood of the Yucatan and wherever one was discovered a habitation soon sprung up; today, Valladolid is the nearest large town near these two particular remarkable structures. We had made our way there from the next town along specifically so that we could go for a swim..... and take a few photos. These caves are basically the local swimming baths and very popular in the summer; on a weekday in spring, though, they were all but deserted. The temperature was in the mid 30s Celsius and we were clad in our finest sun hats and shorts, slathering sun cream onto our pasty forms at every opportunity; some locals were still wearing heavy coats and gloves. So it was with tangible relief that we descended the thirty or so metres into the cool darkness of the first cave down a higgledy piggledy staircase hacked out of the bare rock.

The lines through the water are ropes there to help anyone that gets into trouble

Straining eyes and ears we began to see and hear the bats that make up half of the permanent population of the subterranean grotto we were about to enter. Sympathetically placed lights around the edge of the cave both above and below the water line changed colour every minute or so altering the atmosphere of the cave in a mesmerising sequence. The main feature of the cave was very much the 30m wide almost circular pool of crystal clear freshwater, but it wasn't long before the eye was inevitably drawn upwards to the mass of stalactites that hung almost menacingly, like the Sword of Damocles, from the roof. One area was so thick with the formations that the stalactites had congregated into a tight formation that put me in mind of an organ from one of the worlds great basilicas. This wasn't the only feature that gave this great cavity the feel of a cathedral; the coolness, the respectful quiet, the mass of stone and faint echo of hushed voices all added to the effect. Further, the small opening in the roof through which poured a single perfect shaft of sunlight could almost be a typical rose window so popular in medieval Europe's Gothic masterpieces.

The water was cool, perfectly so. I'm a keen swimmer, I'll be in the Thames again next week, and I have swam in many beautiful locations but none, I think, as tranquil and captivating as this. With the bats and stalactites above and the shark-like fish, the other permanent inhabitants, as black as jet, gently swimming below this was an experience that will stick with me forever. After we'd had our fill we went across the road to the neighbouring cenote; this one didn't have such an impressive array of stalactites but it did have something to make up for it. Hanging straight down from one edge of the hole in the roof there was a mass of  tree roots eagerly seeking out the precious water below; and instead of bats this cave had lots of little birds flitting in and out chirruping as they went. Somehow, perhaps because it's easier to envision the growth of a tree than it is the incremental elongation of a rock formation, this cave felt even older than the first one although they're actually contemporaneous.

I've never seen anything quite like these underwater lagoons and I'm not surprised that they were often considered sacred places in times past. Hundreds of offerings and sacrifices have been found in some cenotes, not just ceramics and jewellery but human remains too, thought to be an attempt at appeasing the gods in times of drought. Before the Europeans built their churches and cathedrals it is easy to see how these caves could have served a similar purpose bringing an air of sanctity to proceedings designed to make the participants feel closer to god. I don't care for gods, but as I swam in the cool waters I certainly could appreciate the elemental nature of this most imposing of pools.