Thursday, August 17, 2017

Answer: Questions about the Yucatán? (#1000)

The Yucatán!  

Foreword:  Once again, a simple sounding SRS Challenge ended up taking me a LONG time to work through.  I'll explain why it took so long below.  But see the tomorrow's post for what this means...

The cenotes of the Yucatán are impressive places.  They are underground and full of water--but gorgeous.  

They're part of a large network of caverns that are mostly filled with water and marked by sinkholes.  The water is incredibly clear and a fascinating place to explore.    

Naturally, my short visit to the cenotes at Dos Ojos (near Cancun) made me very curious about cenotes, the Yucatán, and the whole place in general.  What's up with this place?  

1.  Cenotes seem to appear all over the Yucatán peninsula.  If you look at a map of the area, it seems they all line up just inland from the Riviera Maya coastline.  But I know there are cenotes in the north of the peninsula as well. Is there a larger pattern of cenotes at work here?  If so, what caused that particular pattern of cenotes to form? 
When thinking about "larger patterns" of cenotes, my first inclination is to search for a map.  I did a general search:

     [ map Yucatan cenotes ]

and found lots of tourist maps showing cenotes you could visit, but that's NOT what I'm looking for.  What I need is a map of ALL the cenotes in the peninsula.

To get a fast overview, I switched to Images mode, and saw this SERP:

If you look through this result set, there are really only a couple of maps that show ALL (or at least most) of the cenotes in the entire Yucatán peninsula. As you can see, there are thousands of them!

The original version of this map was by Jake Bailey and David Kring for the NASA/Univ. Arizona Space Imagery Center. 
It was recently modified by the Lunar Planetary Institute for teaching purposes. 

But there are two striking features of this map.  First, there's a pretty dramatic ring of cenotes with the center just off-shore near Merida.  

The other remarkable map of Yucatán cenotes is below, showing the cenotes in white.  It too has the same ring.
A dramatic ring of cenotes (marked by white dots) is associated with the largest peripheral gravity-gradient feature. The origin of the cenote ring remains uncertain, although the link to the underlying buried crater seems clear. (Gravity map adapted from Chicxulub Crater, Mexico, and the Cretaceous - Tertiary boundary, Canadian Space Agency.)

What's going on here?  I didn't expect a giant ring of cenotes.  Luckily, the source of this image gives us a big clue about what's going on here.  As the USGS points out, this is the edge of the impact crater formed by the Chicxulub meteor from 66M years ago.   (BTW, this USGS web page has an old, out-of-date URL link to the source page.  To find the new location of this page, I had to do this search:  [ inurl:chicxulub.htm] -- this limits the search to the site and looks for webpages with the name of the page in the URL, chicxulub.htm - the actual page with the report is LINK.  True as of August 16, 2017)  

But the second major feature of this map is that there seems to be a suspiciously straight-edge where cenotes seem to be missing (see below).  Is this a real feature (e.g., caused by a change in geology at that point), or could it be caused by just missing data?

Answering this question: Are there cenotes in here?  took me a couple of hours.  

In general, it's really hard to find missing data.  As a researcher, you're looking for something that might not exist!  

So I started by searching for other maps of this region.  I'll spare you all of the details, but one of the reasons that this "possibly missing data" is so difficult to track down is that this is not in Quintana Roo--it's mostly in the state of Yucatán and Campeche.  

And, as I found out, there are a LOT of studies of the cenotes in Quintana Roo, a few in Yucatán, and even fewer in Campeche!  I keep getting hints that there ARE cenotes in Campeche, (e.g. this article, Campeche, a Land of Still Unexplored Cenotes) but it’s hard to find a map showing them.  It’s hard even to find a master list of all the cenotes in this state or in Yucatán! Luckily, that article tells us that there are cenotes near the town of Miguel Colorado.  After just a few minutes of zooming around this area on Maps, it's really easy to see that there are a lot of small lakes, many in an arc and round in shape.  (You'd want to verify that these are cenotes, but I'm willing to bet you a dollar that's what they are.)  

Probable cenotes near Miguel Colorado, Campeche, MX.

But I kept searching, doing all kinds of things that didn't work out, and eventually I tried the query: 

      [ cenotes map peninsula ] 

in Google Scholar.  And this query took me to a fascinating article Review: The Yucatan Peninsula karst aquifer, Mexico (published in Hydrogeology Journal, 19.3, 2011).  And THIS article has the following map in it: 

As you can see, yes, there are cenotes in the center of the peninsula--they're just not quite as well organized as the ones in the Holbox or Rio Hondo areas.  (A little more reading tells us that these are fracture zones in limestone where lots of cenotes have formed.) 

Naturally, I want to know HOW this ring of cenotes formed.  

My query: 

     [ origin of the ring of cenotes ] 

took me to the Chicxulub Crater Wikipedia page which tells us that "A team of California researchers including Kevin Pope, Adriana Ocampo, and Charles Duller, surveying regional satellite images in 1996, found a cenote (sinkhole) ring centered on Chicxulub ... the sinkholes were thought to be caused by subsidence of the impact crater wall.  More recent evidence suggests the actual crater is 300 km (190 mi) wide, and the 180 km ring is in fact an inner wall of it..."  (reference: "The Cretaceous-Tertiary Impact Crater and the Cosmic Projectile that Produced It" Annals of the New York Academy of Sciences. 822: 353–80) 

That makes a great deal of sense.  A giant meteor strikes just off the coast of Yucután and causing an impact crater in a heavily limestone area. And by the way, killing off all of the dinosaurs as a side-effect!)  That could lead to caves forming, and ultimately their roof collapse, forming cenotes.  

So, yes, there are multiple patterns in the cenotes.  On the east coast of Quintana Roo, you see them lining up along the fracture lines of the Holbox and Rio Hondo fracture zones.  And amazingly, in the west, you see a giant 300 km wide ring of cenotes, caused (in some way) by the Chicxulub meteor.  

My friend, playwright Ross Nelson, happened to post this remarkable article about the Chicxulub meteor as I was writing this blog post.  

In it, the author argues that the meteor wiped out the dinosaurs not just because it was a large meteor, but because it hit the largely limestone (calcium carbonate)  and gypsum (calcium sulphate) rock layers of the Yucatán peninsula.  This mixture, when heated by a large amount of energy (such as from a meteor impact), would cause the creation of a vast amount of sulfur dioxide (with the sulfur coming from the melted gypsum).  

Sulphur dioxide then slowly reacts in the atmosphere to form a haze of sulphuric acid droplets, scattering sunlight and cooling the Earth. That haze, rather than simply dust, is how the Mt Pinatubo eruption affected climate.

The estimate is that the haze produced by the Chicxulub impact would have blocked enough sunlight to reduce temperatures worldwide by more than 10 degrees C (18oF).  

The surprising claim of the article is that if the meteor were 10 minutes earlier, or 10 minutes later, it would have fallen into the open ocean, boiling a lot of fish (and probably causing other effects), but perhaps without creating all of that sulfur dioxide haze, and consequently all of that cooling.  

Hard to know what the effects of a Chicxulub meteor would have had in the open ocean, but maybe not quite like this... 

2.  As you know, Cancun is on the eastern side of the Yucatán, in the state of Quintana Roo.  That name--Quintana Roo--has always struck me as slightly odd. Where's this name from, and why does it sound so non-Spanish?  (Extra credit:  How do you pronounce "Quintana Roo"?  While there, I learned I've been saying it wrong all these years!)  
Finding this out isn't terribly hard--the query:  [ Quintana Roo ] gives multiple sources telling us that Quintana Roo was made a territory of Mexico by decree of President Porfirio Díaz in 1902, and was named after an early patriot, lawyer and author, Andrés Eligio Quintana Roo.  He ran the Constitutional Assembly that drafted the Mexican Declaration of Independence in 1813.  

Tracking down the history of this name is a bit more complex.  Andrés Eligio Quintana Roo's father was Matías Quintana and his mother was María Ana Roo.  Searching for just her name:  [ María Ana Roo ] leads immediately to a genealogy site that gives a lot of background information.    Here we learn that María Ana Luisa Roo y Rodriguez de la Gala
was born in 1768 in Campeche (in the Yucatán), and that her parents were Antonio Roo y Fonte and Leonarda Rodriguez de la Gala y Torres.  Her father is from San Cristobal de la Laguna in the Canary Islands, and her mother is also from Campeche.  HOWEVER..  Antonio Roo y Fonte's father was Manuel de Roo Villareal.  

That name, "De Roo" is a Dutch or Flemish name, and looks like it was truncated to just Roo along the way.  We also know that there was significant immigration to the Canary Islands from both Holland and Belgium, so it looks like that's where the name comes from!  

How do you pronounce "Quintana Roo"?  The easiest way to find out is to search on YouTube for:  

     [ pronunciation of Quintana Roo ] 

which leads you to a nice YouTube video with someone saying the name.  Here, the title of the video is in Spanish ("Quintana Roo - Pronunciación en español"), which makes me feel more comfortable that it's correct:  

Reader Contribution:  Luckily, we also have a recording by Regular Reader Ramón, who sends us this MP3 with his pronunciation followed by his Mom's pronunciation.  (Thanks, Ramón!  I've been saying it wrong all these years!)  

3.  Speaking of Quintana Roo, when did it become a full-fledged state of the United Mexican States (Estados Unidos Mexicanos)?  
My query: 

     [ history of Quintana Roo ] 

... and then a lot of reading from multiple sources.  (Esp. the Wikipedia pages (both in English and Spanish--luckily, they mostly agree, although as usual, the Spanish language version has much more detail. I also drew from the Nations Encyclopedia.)    

The area that makes up modern Quintana Roo has a shared history with the Yucatán peninsula.  In the 1840s,  the Caste War of Yucatán, all non-natives were driven out of the Yucatán, leading to the foundation of the independent Maya nation of Chan Santa Cruz. For decades it was a separate country, with its own trade and foreign policy.  

Quintana Roo was declared the territory of Quintana Roo by decree of President Porfirio Díaz on November 24, 1902. After several uprisings, the Mexican army succeeded in defeating most of the Maya population of the region during the 1910s (during the time of the Mexican Revolution). In 1915 the area was again declared to be legally part of the state of Yucatán, although still as a separate entity.  

Quintana Roo was granted statehood within the United Mexican States on October 8, 1974, and is the youngest state in Mexico.

4.  While walking around, I found a tree (apparently native) that is said to have been the basis for chewing gum.  Really?  What kind of tree is this? What's the story here?   
Working from what we have, 

     [ chewing gum tree Yucatan ] 

which leads to multiple articles about chicle and the Sapodilla tree. 

Manilkara zapota, commonly known as the sapodilla is a long-lived, evergreen tree native to southern Mexico, Central America and the Caribbean.

An interesting story (and high quality source) was an NPR story about the history of chicle, chewing gum, and sapodilla trees.  In there, we learned that chicle is the latex (sap) of the sapodilla tree, and that Quintana Roo had the largest number of sapodilla trees, effectively the world's production of the basis of chewing gum.  

It's a great story, well worth a read (or a listen).  It has great characters like Antonio Lopez de Santa Anna, the 11-time president of Mexico, who worked with a New Yorker to develop chicle as a replacement for rubber.  He did this while he was exiled in the US trying to raise money to fund an army for a return to power. But using chicle as a rubber replacement never worked, but it turned out that it could be used as chewing gum!  (An excellent book to read is Jennifer Mathews Chicle: The Chewing Gum of the Americas, From the Ancient Maya to William Wrigley (2009).  Check out chapter 2 for even more amazing stories about the sapodillo tree.  

Santa Anna was also, by the way, that Santa Anna who led the battle at the Alamo.  

So, yes, chicle is the basis of chewing gum.  Or it was until the 1960s, when most chewing gum companies switched from using chicle to butadiene-based synthetic rubber which is cheaper to manufacture.  (In a strange twist of fate, Santa Anna tried to develop chicle as a rubber replacement; but now rubber has replace chicle in chewing gum...)  

Search Lessons

There are a lot here, and I'll continue this commentary tomorrow.  But let's start with a few obvious ones... 

1.  Take good notes!  I made a big mistake by not keeping decent notes as I was working on this, which led me to have to back up and repeat a bunch of searches... all because I didn't write down the queries and the results that later proved to be useful.  Notetaking is a powerful skill--especially for people doing research. 

2.  Know when to use INURL:  Recall that sometimes links to pages go out of date.  They usually aren't deleted, but they ARE frequently moved around (e.g., the web page example above).  To find the new location of this page, I had to do this search:  [ inurl:chicxulub.htm] -- that site: limits the search to the site and the inurl:  looks for webpages with the name of the page in the URL, chicxulub.htm - the actual page was still on the site, just elsewhere.  

3.  Finding missing data is hard... so think of another way to frame your queries.  In the case of the apparently "missing" cenotes, I had to search for the names of the other states (Yucatán and Campeche) in order to find much of anything.  It was also handy to get a single cenote (near the town of Miguel Colorado), and then go check Google Maps (or Earth) to see what the ground truth is.  

4.  Remember YouTube as a source for "physical" information.  In looking for the pronunciation of Quintana Roo, you can look for the International Phonetic Alphabet version (kin.ta.naˈro.(o) - but remember that this is IPA for Spanish).  In such cases, it's easier to find someone to just DO it in a video.  

More tomorrow... in our next exciting chapter of SearchResearch! 

Search on. 


  1. Dan, I am always impressed by the amount of detail you devote to these Challenges. This cenote inspired one is fascinating too. How do you find time for your extracurricular activities like travel and lecturing and running around the countrysides. Congratulations and thank you for the first thousand Searches. Cheers jon tU

    1. Well... it's turning into a bit of a problem.. AND a new adventure. Stay tuned for tomorrow's post!

  2. This program was broadcast last night in Australia
    Not sure if it is geoblocked but they talk about the gypsum at about 44:30


  3. Very interesting question about the formation of the Ring of Cenotes. We DO know that is a surficial expression of the Chicxulub Impact Structure, somehow related, but there is NO mechanism to explain how a deep-buried crater (over ~3km of limestone) transfers geometric information to the surface. There are many hypothesis yet to be tested, you already mentioned some of them. I'm currently working on a different approach: a hydrogeothermal model involving platform-scale circulation of water, enhanced and concentrated by the impact. Hope to publish the paper very soon. Nice blog, btw. Greetings!

    1. Fascinating. The first article is well-worth reading, and your site looks super relevant. Good luck in your research on the Ring of Cenotes!