What do Cenotes in Yucatan and Dinosaurs have in common?

We got to see five Cenotes on this trip and we went swimming in one of them.  While sitting there looking at one of the wonders that made the Maya civilizations possible I began to wonder why were they here? and why are there so many of them?  Over one thousand identified!  The Yucatan Peninsula is a porous limestone shelf and all freshwater rivers are underground.  The Mayas called them "dzonot,"  and they are now called "xenotes" or "cenotes."  To the Maya they were magical and the only source of fresh water.  Cenotes also represent the entrance to the underworld just like the high mountains (or pyramids) represent the entrance to the heavens.  

The Maya, at least in the early classical period, only used these Cenotes as a source of water for drinking and irrigation.  It is thought that the Toltec influence in the Post Classic period introduced the use of Cenotes as a place for human sacrifice to their rain god Chaac.

Based on my title for this posting, so what do Cenotes have to do with dinosaurs? 

One theory, supported with lots of data, is that the one key thing that killed off the dinosaurs was the impact of a meteor six miles in diameter.   It turns out that most of the cenotes in the Yucatan are lined up on the rim of the Chicxulub Crater, the place where this six mile diameter meteor hit the earth and destroyed not only the dinosaurs but most of the animal and plant life on the earth!   Cenotes are mostly found on the meteor crater rim.  Driving back from Uxmal (pronounced ooshmahl ) one actually drives over the remains of the crater rim from 65 million years ago and it is a high ground where you can see for many miles around.  It is kind of cool to be sitting near the edge of this crater – ground zero of almost total destruction of the earth.  

As I sat there looking out at the horizon I also thought of the southern fundamentalist Baptist preachers and their “preaching” of fire and brimstone and what a terrible place hell can be for sinners.  Well, let me tell you, they have no concept of the meaning of fire and brimstone.  And hell is a walk in the park compared to what happened here.   To get an idea of what destruction really is  one has to imagine what this meteor really did.  The 6-mile wide meteor hit the earth at about 50,000 mph, generating the power over 3 billion (note not million, billion) WW2-type atomic bombs.  First, the impact would have created a cloud of super-heated dust, ash and steam would have spread from the crater as the meteor impacted with the surface and carved a crater 12 miles deep and 190 miles in diameter in less than a quarter of a second.  The heat from the blast would have incinerated everything within a thousand miles instantly and would burn all those happy dinosaurs grazing, within a 3000 mile radius, as far away as where Montana (or at least where Montana would be 65 million years later), within minutes of the blast.    The poor dinosaurs didn’t even have time to get frighten!  

After the initial blast that killed everything in the way, including plant life and sea creatures, much of the excavated material along with pieces of the meteor would have been ejected out of the atmosphere by the blast, they would then return, super-heated upon re-entry, and would have broiled the surface of the earth igniting wildfires everywhere on the planet.   Incredibly large shock waves would have triggered global earthquakes and volcanic eruptions all over the earth coating a large portion of the surface with magma - liquid rock.  The impact would have caused the largest tsunamis in Earth's history, probably over a thousand feet high flooding most of the continents, since large mountain ranges did not exist yet.  And this is the good news – instant death to dinosaurs within 3000 miles.

The bad news was yet to come.  The emission of dust would have covered the entire surface of the Earth for up to ten years, creating a permanent dark winter all over the earth with temperatures much below zero.  The plants would die, the herbivores, those that survived, would die of starvation.  The carnivores, would have nothing to eat and they would die of starvation – on both the land in the water.    

Moreover, in addition to creating a 10-year long winter, was the production of sulfate aerosols in the upper atmosphere causing acid rain further destroying the ability to survive.  On top of all that destruction, there would be a reduction of oxygen in the atmosphere.  The reason dinosaurs grew so large was that the atmosphere had a higher concentration of oxygen allowing the dinosaurs to grow and maintain their large size.  Even if some big dinosaurs managed to survive, they would not be able to sustain themselves in a reduced oxygen environment.  Bottom line, dinosaurs did not have a chance!, just like we would not have a chance if a similar asteroid would hit the earth today!  

So why are the most of the cenotes arranged in a circular pattern on the outside of the crater trough?  I believe that when the crater was formed it pushed a lot of the limestone out and the newly deposited limestone on the outside of the crater was not as packed as the original layers of limestone or compressed as the limestone inside the crater must have been.  These weak layers were more susceptible to dissolution by the underground water, dissolving and forming cavities and further being dissolved leaving the large cavities that we now call cenotes.  in some cases these cavities collapsed and formed sinkhole-type cenotes and and in some other cases they refilled again.

Yes Cenotes are beautiful places, but we have to remember that they are the product of the geologic conditions created by the impact of the meteor and true hell on earth.  The beauty of Cenotes represents the total destruction of almost all life on earth.  And, I'm sitting here imagining this total destruction, it is like an HD video streaming in my mind.  I look at this beautiful place and I visualize it 65 million years ago.  I wish I could have been on a satellite watching this whole thing!