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Data for Divers: Mexican Explorers Go Digital to Chart Riviera Maya

Mexico’s Yucatan Peninsula has long been the focus of underground exploration. Now a host of new tools such as digital surveying tools, mapping software, photogrammetry, drones, and augmented reality systems are making it easier for explorers to both collect data and share their findings with the world. InDepth sat down with veteran Yucatan explorer and geospatial scientist Sam Meacham to discuss his foundation’s extraordinary exploration efforts and get the lay of the land.

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By Michael Menduno

Photo by Sam Meacham CINDAQ AC

When I asked Sam Meacham how old he was during the course of our interview, he immediately quipped, “old enough to know better than to have dedicated my life to cave diving.” Fortunately, or unfortunately for Meacham, it would appear that his predilection won out. 

The ardent 53-year old explorer, diving instructor, conservationist, geospatial scientist, mapmaker and founder of El Centro Investigador del Sistema Acuífero de Quintana Roo, aka CINDAQ—whose mission is to facilitate research, promote education, and support conservation of the cenotes and underground rivers of Quintana Roo, Mexico,has spent more than a quarter of a century peering off into the darkness and returning to tell the tale. In CINDAQ’s case, this typically takes the form of map data, logs, pictures, photogrammetry, geospatial data, video, film, and documentaries (BBC, CNN, National Geographic and PBS), lending support to famed explorer Bill Stone’s observation that “the difference between exploration and adventure is data!”

Sam Meacham (front) before a dive.

In that regard, Meacham and his pioneering colleagues, Fred Devos and Chris Le Maillot, owners of Zero Gravity dive center, and others, have been extraordinarily prolific, shedding light on many hundreds of kilometers/miles of underground passageway that form the circulatory system of Riviera Maya, to the benefit of policy makers, scientists, and citizens alike. “We are building on the pioneering efforts of those who came before us and trying to build up the generation that will follow,” Meacham explained. 

In fact, over the last three years as a result of increased funding, new tools, and an enthusiastic pool of trained volunteers, they have actually stepped up their exploration and documentation efforts. Meacham, who was born in the U.S. and is also a naturalized citizen of Mexico and France, says they are just scratching the surface.

The New Frontier

One might say that the Yucatan, once considered the “new frontier” of cave diving back in the 1990s, occupies a special place in Sam Meacham’s diving firmament. In 1984, Meacham, then a lanky teenager, made his first dive during a PADI “Discover Scuba Diving” course while on family vacation in Akumal where he first met cave diving pioneer Mike Madden. He got PADI Open Water certification in Anguilla a year later. He was hooked.

Meacham returned to Puerto Aventuras nearly a decade later in 1994 to become a recreational diving instructor under Madden’s tutelage. That same year he completed his full cave certification with then National Association of Cave Diving (NACD) president Steve Gerrard. Meacham began work as an instructor at Madden’s CEDAM Dive Center, and later worked for Aquatech Villa DeRosa, where he learned from two additional cave diving mentors Gary and Kay Walten. It is also where Meacham first met Bil Phillips with whom he would share many adventures.

An RB-80 heads into Cenote Gea to explore. Photo Courtesy of CINDAQ.

The 1990s was a period of intense cave exploration in the Yucatan, as competing teams of divers sought to connect two gargantuan cave systems, Nohoch Nah Chich and Dos Ojos, and by doing so claim naming rights for the combined system. Meacham was in the thick of it.

Deciding to branch out on their own, Meacham, Phillips, Fred Devos, Bernd Birnbach, Chris Le Maillot, Daniel Riordan and Sabine Schnittger began the early exploration of the Ox Bel Ha system, which CINDAQ has carried on to this day. “I am extremely proud of what we accomplished,” Meacham said. “We were too young to know it was almost impossible.” Most of the expedition work at that time was self-funded. The group ended up buying a horse (to ferry gear into the jungle) and a compressor.

Forming CINDAQ

In 2000, Meacham founded CINDAQ, a nonprofit foundation and recognized non-government organization (NGO), to provide a legitimate mechanism to solicit and accept funding to cover the cost of exploration projects. Their first sponsor was Aguakan, the company that supplied water to Cancun, and which wanted the team to explore and map the area around the company’s wells and help create a campaign to raise awareness of water issues. 

Over the next eight years, CINDAQ was able to secure funding from numerous sponsors to continue their far-flung exploration of Ox Bel Ha, and later Sian Ka’an, including renting a helicopter to ferry divers gear to a jungle-locked cenote. He also participated in a number of documentaries including “Secrets of the Maya Underworld” and “Planet Earth: Caves” for various BBC units, “The Spirit of Nature,” for CNN, and forNational Geographic/PBS, “Strange Days on Planet Earth.” Many of these were filmed with Mike Madden with whom Meacham shares a passion of storytelling through film.

In 2009, Meacham was given the opportunity to go to graduate school and was accepted into a master’s degree program at the University of New Hampshire to earn a M.S. in Natural Resources with a specialization in geospatial science. His thesis: “Using Landsat 5 TM Data to identify and Map Areas of Mangroves in Tulum, Quintana Roo, Mexico,” used satellite data to locate and map mangrove in the Municipality of Tulum and down into the Sian Ka’an Biosphere Reserve. During this period, he put CINDAQ on hold. Upon graduation in 2012, he was offered a job as a research scientist and diving safety officer, at the Meadows Center for Water and the Environment at Texas State University.

CINDAQ Redux

In 2016, Meacham and his family moved back to their house in Mexico, and he began a reinvigorated effort to bring CINDAQ back to life. Meacham, who was now a Global Underwater Explorer (GUE) instructor and a member of the GUE board of directors, along with Devos and Le Maillot,were able to solicit private donations and, in cooperation with the volunteers at the Mexican Cave Exploration Project (MCEP), stepped up their exploration and mapping efforts. They focused on Ox Bel Ha and connecting caves further south into Sian Ka’an, which lies deep in the Mayan forest.  Meacham calls Sian Ka’an the “Mount Everest of Cave Diving.” 

Divers returning Cenote Yax Kai, Ox Bel Ha Cave System. Photo by Su Eun Kim.

“Sian Ka’an is pushing us geographically and logistically,” he explained. “It’s what Madden taught us early on. If you want to scoop booty, you’ve got to go where the booty is.”  CINDAQ also supports the Hoyo Negro Project, started by fellow GUE instructor Alberto Nava, which graced the cover of National Geographic in 2015, and was the subject t of a NOVA/PBS special “First Face of America,” which aired in 2018; Meacham teamed up with Madden for this project and was an assistant to the camera man and managed logistics. “I’m thankful for the opportunities that cave diving has afforded me,” he said.

Key to CINDAQ’s current efforts is a host of new imaging, digital data collection, and presentation tools and technologies to aid in the exploration and create public awareness. InDepth caught up with Meacham earlier this year to discuss the team’s latest efforts.

InDepth: Has CINDAQ lived up to your expectations?

Sam Meacham: Absolutely, yes, and beyond. It exceeded my expectations. We established CINDAQ for pretty practical reasons and then it just kind of took off from there. And at the outset we had funds from Nature Conservancy, National Geographic Society, private funders and also the Summit Foundation in Washington D.C. We are extremely grateful for all of their support, and the support of our incredible volunteer divers through the Mexican Cave Diving Project (MCEP), which Chris Le Maillot and Fred Devos set up. Without both of these men we wouldn’t be able to accomplish even a fraction of what we do here.

It’s like living in a dream. Sometimes you shoot for the moon and you get the stars. So right now, we’re getting out into the stars and, in fact, several galaxies away. 

I know that you’ve done an incredible amount of new exploration as well as going back and re-surveying the previous work of your team and others. Do you have any statistics that you can share with us

Yeah, exploration is one of our main focuses right now because of the massive amounts of development that are taking place around Tulum, where the majority of the cave systems in this area are located. We are concerned about development and how it’s going to affect, not only the caves themselves, but most importantly the aquifer and the water that flows through our caves.

To give you a perspective, in 2018, out of a total of 18,000m/59,000 ft of total survey, 12,000m/39,300 ft was new exploration, and 6,000m/20,000 ft was resurvey of existing lines.  By contrast, in 2019, we did a total of 80,000 m/262,000 feet of total survey; 30,000m/98,400 ft was new exploration and 50,000m/164,000 feet was re-survey. Then in January of this year, in just 14 days of diving, we resurveyed 8,445m/27,700 ft and explored 11,277m/37,000 ft of new passageway.  So, it’s kind of been growing exponentially.  And all of this is just in the Ox Bel Ha system.

So, what seemed like a preposterous proposal just a year and a half, two years ago: that we could resurvey an entire cave system the size of Ox Bel Ha, which is well over 300,000m/984,252 ft now, does not seem like such a crazy proposition anymore.

Amazing. I remember when I was coming up in the 90s, the Yucatan was regarded as the new frontier of cave diving, there was so much exploration going on. Now almost 30 years later, I am guessing much of the diving community, thinks, well it’s all been explored down there. And that’s obviously not the case. Any idea of how much remaining exploration there is to be done?

My response is a whole hearted, HAH! We’re still just scratching the surface. In fact, it doesn’t take much math, but you can figure out the ratio: for every one meter that we resurvey there’s just a bit less than one meter of line that gets explored. We’re going back into the caves and marking leads and getting into new areas and expanding the extent of the caves. That’s what we’re really most interested in because of all of the development happening at the surface. We really want to do a good job so we can show the general public and the landowners exactly what’s going on beneath them as accurately as we possibly can.

So just to clarify, we’re talking about new exploration in known cave systems, versus systems that have yet to be discovered.

Correct. Just as an example, we have been in the area of Ox Bel Ha we are diving right now for, I don’t know, the last two or three months. The last time we were in one of the entrances in this area was in 2009; I don’t think we’ve been in the other entrance since 2002 or 2003. No one has been in there. The reason we haven’t gone back is because it’s just really hard to get to. Development is a double-edged sword. On the one hand, it means more humans and more waste and pollution, but it also means new roads. 

We now have a new road that runs through the middle of the jungle that takes us to three separate entrances and gives us access to a whole section of the cave that previously required a 45-minute hike to get to. So, yes, we are revisiting areas that we were in before, but we’ve never had the time and energy and ability to explore them to their full extent. Most of the original exploration that was going on there was all focused on the main tunnel, the gravy, the easy stuff. Now we’re focusing on linking up different sections of the cave to make it one.

September 2019, Cenote Gemini, eagle eye view from above courtesy of the drone. Photo courtesy of CINDAQ.

I heard that you started re-surveying old lines to test out some new surveying technology, the Mnemo and the Ariane cave mapping software, I want to talk about those. But why have you continued to re-survey?

That’s right. We started resurveying a small portion of the cave in 2018. The real objective was to see if the Mnemo and Ariane were good tools for us to use. We concluded pretty quickly that they were.  The benefit is that by going in and re-surveying the caves, we’re not only shoring up the data that we already have, but we can compare the historical data to the new data we are getting. 

It turns out that our historic data really wasn’t all that bad, but we benefit from better GPS now. It’s a lot more accurate, so we can correct things. In some cases, the original line survey had errors, which then threw the rest of the data off. Perhaps the coolest thing is that we are going back into areas of the cave that we haven’t been to for years as a result of better access, as I mentioned, and the fact that we have maintained good landowner relationships.

Tell me about Mnemo.

Well, for us, it started as a pet project in 2018. We’re very fortunate to have Sebastian Kister here who developed the Mnemo and also Ariane, the software that Mnemo communicates with, living right here in the Riviera Maya. At the time, I had heard about Mnemo and Ariane and I thought, okay, perhaps it will help us to get a handle on all the data that we have and help us be more efficient with time both in and out of the water. 

The mnemo in use doing cave survey. Photo by Christophe Le Maillot

Mnemo is an ingenious and simple device that has an internal compass, an internal pressure sensor, so it can measure depth and azimuth, but perhaps the most ingenious part of all, is its ability to measure distance. That has always been a bit of a conundrum. The traditional means, of course, is knotting the line at fixed distances, but that leads to error, as it’s easy to lose count.

What Sebastian came up with is a wheel that looks a bit like a piece of pizza with slices on it, and it spins around. It has a white slice and then a slice with nothing in it at all, and there are two light sensors, which count the white slice every time, which is a known distance that goes by. You attach the Mnemo to the line, and swim the line, while the device records distance, depth, and azimuth. It takes a little practice, but it’s  not hard to master. Last year I think we trained about 20 people to use it.

So you can swim or scooter and it just records as you go?

Yes. Scootering takes a little bit more practice, and you’ve got to be really careful because, of course, it has an internal compass, so you have to be very careful with anything magnetic, like a scooter’s battery and other electromagnetic components, in order to not interfere with the accuracy of the compass. You can survey on the scooter as long as you have big passageways. This allows us to cover a lot of distance in one dive. 

Then you just connect it to the computer after the dive and it uploads the data to Ariane’s Line?

Yeah, it goes right in. You have to tell Ariane where the data starts, so, like any cave survey, you have to know where the tie-in data is. But as long as you know that, you can keep track of the lines that you resurveyed with the Mnemo, and within a matter of minutes you can easily enter a ton of survey data—boom—in no time at all. Normally, it would take quite a while to transcribe the handwritten cave survey data into Excel and then copy and paste it into another survey program, and then upload it. This process was also prone to errors. Mnemo is much more accurate than anything we were able to do previously. To give you an idea of its accuracy, we recently completed a massive 5,000+ meter loop.  The loop closure error was less than 1%.  We would have had a hard time doing that with a hand survey.  The Mnemo just makes a lot of sense. And it has really streamlined our process in and out of the water. 

Photo courtesy of CINDAQ.
Are you able to upload the old survey data into Ariane’s Line as well?

Yes. Sebastian made it so that we could import the original cave data into Ariane. It’s fantastic because it gives us a means of comparison. Like I said, our original survey was actually pretty damn good given that it was done 20 years ago often with 35 W halogen bulbs and a single person surveying out after a solo exploration dive. 

I’m actually really proud of the survey that was originally generated. Interestingly though, some of the most valuable information in our survey work is the comments, for example like what you are seeing around you, the geology, the navigation symbols, directional markers, those sorts of things that help you to navigate the cave. So, by resurveying we are really enriching the survey comments which has a lot of benefits to safety and our general understanding of the cave.

We are also benefiting from advances in technology. We’re going back into the passageways with better lights, better batteries, and better scooters.  We’re using open circuit side mount, back mount and also RB-80s (semi-closed rebreather) in back mount and custom sidemount versions.

We have a great deal of versatility depending on what the cave throws at us. Especially with the RB80s, we can just spend up to seven hours of true working time underwater and get a lot done.

And I see you are employing lots of volunteers to help with the work! 
January 2020, Mark Garland and Alison Perkins after a productive week of diving from Cenote Coca Ha. This was on the last day of diving and all safety stages and scooters were removed. Photo by Sigurd Bowitz.

As with everything in Global Underwater Explorers (GUE), it’s a team effort and we’re extremely fortunate to have the team of people around us that support us and make it all possible. We have this fantastic wellspring of divers through our partners, the Mexican Cave Exploration Project (MCEP) who have amazing skills and are seeking purpose for using those skills. This is one place where we can totally put them to work. It’s a bit like Tom Sawyer convincing his friends to paint the fence. We’re doing the same thing with cave surveys. In fact, I have divers that just came back from a dive with data for me. They’re totally into it. They are just loving it. 

The fact we are using Mnemo means that they can immediately see what they surveyed that day. Previously, with the manual survey, it would take hours to get all the data, and that was just a total pain in the ass. We’ve finally found the tools and we have this incredible army of volunteer divers who come here and help us achieve our goal. So that’s our main thrust at Ox Bel Ha, resurveying and exploring.

You have also been deploying drones and using drone software for finding new areas too, haven’t you? Talk to me a little about that.

Hah! We’re everywhere. We bought our first drone in 2017. And I’d like to call it the revenge on my parents who never bought me anything that was remote-controlled. Hence the drone.  I guess you can’t take the boy in me away.

Cenote Yax Chen, Ox Bel Ha Cave System. Photo courtesy of CINDAQ.

At the outset, we thought it was a pretty cool tool just to help us to have periscopic vision in the jungle. As you well know, the jungle here is extremely monochrome and flat. And even if you crawl just to the top of the tallest tree in the forest, you’re only a few inches above all the other trees. With a drone we can get above that and gain this incredible perspective of everything that’s down below. 

It’s unbelievable that the technology, as it is right now, enables us to discover and document cenotes from a perspective that previously would have required a helicopter or an airplane, which would obviously be prohibitively expensive. 

So last year, we applied for and received an enterprise license from a company called DroneDeploy based in San Francisco. It enables us to plan flights and create geo-referenced orthophotos of the surface. This allows us to have an accurate and up-to-date snapshot of what is happening on the ground and how it relates to what we are seeing in the cave.  Ariane and ArcGIS allow us to overlay all of this data on the cave.  I’ve been telling people it’s like Project Baseline, but in the sky. We can monitor a site and see what’s happening from year to year. DroneDeploy also has a rudimentary filter that allows us to see the health of vegetation which is immensely helpful in seeing where cenotes might be. Foliage around cenotes is going to be a lot healthier than the rest of the jungle simply because those plants have ready access to water. And it gives us a rough idea of elevation at the treetops which is another indication. Taller vegetation tends to be around cenotes.

We can also use DroneDeploy to create a three-dimensional model of the terrain. We are doing a lot of photogrammetry of underwater passageways, so what we are going to conceivably be able to do in the future is to take a three-dimensional model of the surface and merge it with a three-dimensional model of the cave and have a real virtual experience where you can literally fly over the jungle and then down into a cenote and into the cave that is below it.

Close up of overlay of cave data displaying depth over drone imagery. Photo courtesy of CINDAQ.
Augmented reality (AR) is something you all got to play with last year using the 360° Boxfish camera, right? The Oculus Go demo that you gave me was just awesome.

Yes, we had the opportunity to demo a Boxfish 360 camera last May, thanks to Russell Hughes of Boxfish Research. He put it into our hands and let us run wild.  The results have been amazing. Augmented reality is different from virtual reality because we are just going along for the ride, and experiencing what the 360 cameras see.  From an educational standpoint, this is a game changer for us. 

Watch a 360° Camera Cavern Dive in Mexico’s Riviera Maya

Photo by Michael Menduno/M2

The interesting thing is that even experienced cave divers are seeing things that they’ve never seen before. We don’t usually stare up at the ceiling when we’re cave diving, so giving divers that perspective is pretty cool. One of the most rewarding things I have been able to do is to take my octogenarian parents, who have always been very supportive of me and what I do, cave diving with the augmented reality goggles.

And enable them to experience what a cave dive is actually like!

I can show people videos and photographs, write articles or do documentary films about what it is we do, and the environment we go into, but nothing has come anywhere as close as really connecting people to our world than the augmented reality stuff. My father was actually brought to tears. So, in just thinking about non-divers and raising awareness about this hidden world, we get pretty excited. Part of CINDAQ’s mission is educating people about the aquifer.  And we’ve always had this incredible stumbling block helping people grasp what we experience when we go down there. We’re now convinced that we finally have a means by which we can educate people about the aquifer and the caves.

The amazing Sun Cave at the University of California San Diego’s Cultural Heritage Engineering Initiative (CHEI). This is as close to a Star Trek ‘holodeck’ that any of us will ever get. Photo courtesy of CINDAQ.
So for example, Mexican policy makers that are actually making policy that could affect the aquifer.

Correct, yes. For anybody that’s a non-cave diver, we can take them cave diving now without fear of them dying, which is good.

Always a good thing! 

Yeah, and let’s not forget the scientists that we work with as well. We’re using a lot of photogrammetry to create models of the spaces that we go into. However, to enhance that with the augmented reality footage is absolutely fantastic. We’re just in this perfect storm of really cool technology that’s helping us to tell our story and, more importantly, to tell the story of these caves and the role they play, in a way that we never have before. 

I’m not kidding when I tell people—and I say this almost on a daily basis—that I have never been more excited about what I do than I am right now. We are currently testing out all this cool stuff in Mexico, but there is no reason that it can’t be done in underwater caves all over the world to highlight the importance of groundwater. At the end of the day, that is the issue: our freshwater resources, since 20% of the human population depends on groundwater.

Have you seen any impact yet? Have you created awareness among the authorities there, the people you deal with, the locals, the policymakers? 

Yes, local authorities are obviously aware of the fact that the cenotes are a huge economic driver for this area, and the diving industry is strong here. So, I think they understand the economic benefit of cenotes. Where people start to get a little confused is the incredible extent and magnitude of these massive cave systems like Ox Bel Ha and Sacactun. 

But the idea, which started back in the early 2000s, is to show people the interconnectivity of everything. If you dump sewage in the jungle here, it’s going to come out in the ocean over here, and that’s not such a great thing if you want tourists to enjoy your beaches. 

We’ve worked really hard to raise awareness about the importance of the aquifer here. We’re still lightyears from understanding how it all works, but yes, we’ve had an impact by helping to make freshwater resources an issue here. It’s challenging because there are no rivers and streams here; people can’t see the water beneath them. So it’s that much easier to contaminate and pollute because it’s out of sight and out of mind. 

You have to enable people to see what’s going on!

Yes, that was the thing we realized early on; we had to find a way to bring the cave up to the surface so everybody could see it. We had to make people conscious of the fact that these things even exist, and that they exist on a massive scale that interconnect every single ecosystem that the tourist economy here depends upon. 

Blake Wilson in Cenote Far, Ox Bel Ha Cave System. Photo by Sam Meacham CINDAQ AC.

If we don’t take care of the aquifer, which is the common thread to all of these ecosystems, then we’ve killed the goose that laid the golden egg. This area accounts for approximately 12% of Mexico’s gross domestic product and it’s all tourist based. So it’s hugely important to the regional and national economy that this place be as sustainable as possible. That’s where it’s hard to gain traction with decision makers: to convince people to have a long-term vision for the area versus a short-term vision. 

Fortunately, we now have much better tools to engage the public and decision-makers and hopefully make people want to preserve and protect these incredible natural wonders that they can’t see. Nobody’s going to care about it unless they can feel something for it. That is our very difficult job; making people care about these incredible places underwater that are invisible to them.

That’s what gets you excited?

I lie awake at night thinking about the fact it’s not necessarily the things that we have found, it’s the things we haven’t found yet, the things waiting to be discovered that will be important to science. Whether it’s biological, paleontological, archaeological or hydrological, any kind of “-ology.” Those are the things that are so exciting. It’s the prospect of what we might find. 

You can find Sam and CINDAQ Here:

Website: www.cindaq.org

Instagram: cindaq_mexico

Facebook: El Centro Investigador del Sistema Acuífero de Quintana Roo

YouTube: CINDAQ A.C. 

Additional Resources

CINDAQ And DroneDeploy  

Ariane’s Line: http://arianesline.azurewebsites.net

Mnemo: https://www.youtube.com/watch?v=uHNfQYkH2NI


Michael Menduno is InDepth’s editor-in-chief and an award-winning reporter and technologist who has written about diving and diving technology for 30 years. He coined the term “technical diving.” His magazine aquaCORPS: The Journal for Technical Diving (1990-1996), helped usher tech diving into mainstream sports diving. He also produced the first Tek, EUROTek, and ASIATek conferences, and organized Rebreather Forums 1.0 and 2.0. Michael received the OZTEKMedia Excellence Award in 2011, the EUROTek Lifetime Achievement Award in 2012, and the TEKDive USA Media Award in 2018. In addition to his responsibilities at InDepth, Menduno is a contributing editor for DAN Europe’s Alert Diver magazine and X-Ray Magazine, and writes for DeeperBlue.com

Cave

They Discovered an 11,000-year-old Submerged Ochre Mine

The exploration crew at CINDAQ, headquartered at Zero Gravity Dive Center in Puerto Aventuras made international news this year with their discovery of an ancient submerged ochre mine. Fortunately, they were happy to share the secrets of its discovery and how they documented their find with British cave and 3D photogrammetry instructor John Kendall. Oculus Rifts anyone?

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By John Kendall
Header image courtesy of
CINDAQ

In 2017, underwater cave explorers Fred Devos, Christophe Le Maillot, and Sam Meacham found evidence of ancient mining activity while exploring and mapping new tunnels of an underwater cave near Akumal, Quintana Roo, Mexico.​ Historians know that ancient residents actively mined pigment and other minerals from the caves of the Yucatan Peninsula, but the ancient mines the CINDAQ team discovered are now submerged, indicating that such mineral exploitation occurred thousands of years ago. 

At the end of the last Ice Age, intrepid miners ventured deep into these tunnels with torches in hand. The navigational markers, mining debris, fire pits, and excavation pits they left behind are now entirely underwater. Over the last three years, the three explorers (along with others) have been surveying the site and making 3D photogrammetric models of the mine workings. As the mine has been submerged for around 8,000 years, it’s been untouched since then, and it’s an amazing time capsule. The project recently hit the international news when the first results were published. I was pleased to be able to chat with Chris, Fred, and Sam to find out a bit more about the project, and the challenges faced with archaeological work in a cave environment.

The InDepth Word Cloud: A map of the frequency of words spoken in this interview.

John Kendall: How did you happen to find the mine?

Fred Devos prepping for a dive.

Chris Le Maillot: As always, there was a little bit of chance involved with it. The cave—Sagitario, which is a beautiful cave behind Minotauro—was initially explored by a few local cave divers. They established an upstream and part of a downstream, dropping down in the upstream to around 22 m/72 ft, and there’s the halocline sitting at that depth. It’s not always the case, but they didn’t take any survey, absolutely nothing. So I don’t think the information was there for them to continue on with the exploration. As you know, once you have that data in and have a good concept of what the cave is doing and where it’s going, it’s easier for you to poke around and find potential continuations of the cave passages. 

Chris Le Maillot.

So one of the divers asked Fred [Devos] to get involved to create a survey. That comes from the fact that Fred previously had done some mapping for these guys. Fred had a cave survey class coming up, so he took the class there, and spent the week with the survey class mapping the downstream part. Obviously, when they got to the end of the line, Fred could see that there was potential for further exploration. But you can’t really go off exploring during a class, so he went back with Sam [Meacham].

Sam Meacham before a dive with the team in La Mina.

So then you went back and explored?

Fred Devos: Exploring caves is what we’ve been doing for more than 20 years, and so it’s a regular event during the mapping of a cave to find more cave to explore. You know, when mapping, we have to swim off to measure the side walls, sometimes there isn’t a wall, and then end up exploring that passage. I was in the process of making a detailed map of this cave, and found this passage, so I went back with Sam, and we immediately realized something was unusual. Things were out of place, we started seeing rocks piled on top of each other, speleothems in places they shouldn’t have been, and the further we went the more of this we saw. 

“Exploring caves is what we’ve been doing for more than 20 years, and so it’s a regular event during the mapping of a cave to find more cave to explore.”

We started picking up a little bit of flow, which is always a good thing in exploration, and that led us to this restriction, where all the water was going through, and I don’t think we’d have made it through if the restriction hadn’t been manipulated before we got there. So, you know, speleothems were smashed out, and it really looked like 100 divers had gone through there before us, which really piqued our curiosity as we knew no one had been there before us. We happened to be in back mount during this dive and I managed to squeeze through there and called Sam through, and that was when we first saw irrefutable evidence of what humans had been doing in this cave—you know, pre-8,000 years ago. 

“It was pretty clear to anyone what we were seeing, that people had been digging in here, smashing open the floor and pulling out huge amounts of sediment and piling stuff out of the way. It was super exciting.”

An ochre extraction pit found by divers from Centro Investigador del Sistema Acuífero de Q Roo (CINDAQ A.C.) in the oldest ochre mine ever found in the Americas, dating back 10,000-12,000 years. Photo courtesy of CINDAQ.

We didn’t have to wait for lab results to come back or ask an archaeologist about it. It was pretty clear to anyone what we were seeing, that people had been digging in here, smashing open the floor and pulling out huge amounts of sediment and piling stuff out of the way. It was super exciting, as it was something we’d suspected for quite a while but had never really determined for sure that was what we were seeing. But this time it was obvious, and there was no question about it. 

So, how large an area does the mine occupy?

Sam Meacham: It’s about 250 m/817 ft of cave passageways that are exemplary of the mining activity, and everything we’re seeing there shows the things that people were doing in the mine. 

Devos: And we haven’t finished exploring yet. There are hectares of mining area, so it’s not just one hole that’s been dug out. It’s entire passages and we’re talking about hundreds, maybe thousands of tons of material, and remember we have dates spanning maybe a 2,000-year period.

What makes La Mina so significant from a scientific point of view?

Devos: The amount of workings means that this was a massive undertaking. Not just the mining itself, but it’s clear it wasn’t just a one-person adventure. It must have been multi-generational, but beyond that it speaks very much about the organization of the people of that time. So as you can imagine, they were in a dark cave and needed fire for light. So they needed people to bring in the firewood, and others to cart out the material, and there were probably explorers at the time. You know, people that ventured further into the caves away from the exit into the smaller passages…to find this very valuable resource. And I imagine they were the ones that were being punished somehow because the risk involved was probably much greater. So, you know, if they didn’t do their work well in the mine, they probably got sent to explore.

A diver making notes as he examines an ochre extraction pit . Photo courtesy of CINDAQ

So are there any archaeological signs on the surface around the mine?

Devos: Well there probably are, there’s certainly Maya era archaeology, and in almost every cave we see evidence of that, but we’re talking about 5,000 years ago. The mine was even further back, so anything that was once there won’t be anymore, and the only place we are likely to find anything is in the caves.

Let’s chat about the photogrammetry side. More and more people are hearing about photogrammetry, but I think the readers will be interested to hear a bit more about the challenges that you faced doing photogrammetry in a cave environment, where everything around you is archaeological.

Meacham: I think that can get us started on an interesting concept. In 2010, Chris, Fred, and I, Beto Nava, as well and Franco Attolini and Danny Riordan and Roberto Chavez, all did our underwater archeology course here in Mexico with the Nautical Archeology Society that was supported by the National Institute of Anthropology and History (INAH). It empowered us. 

And by having that NAS certification, it kind of helped check a box for the Institute. And, you know, they could say if anybody questioned our abilities, well, we’ve got the certification. 

I’d say the genesis of this for all of us here was the Hoyo Negro project, and with the exploration followed by the high grade survey, and then the photogrammetry, which is another whole level in itself. The major problem in Negro is the pit itself—it’s just immense—and how do you document something like that? So we worked with Beto and the team who came up with a grid system at 34 m/110 ft depth, and then it’s every 0.8 m/2.5 ft with a cookie on the line, and so it’s a systematic grid. The difficulty there is that it’s not just a nice flat bottom, it goes from 40 m/130 ft to about 55 m/179 ft, and it just becomes really complex. 

But basically what I’ve been doing there is assisting with the lighting or helping Beto. So when we jump forward to doing the mine, it’s a completely different environment. There’s no pit—it’s a continuous cave—so there was no way we could put in a grid, and I’ve never really done photogrammetry before. I had observed it being done, but I was starting from scratch in terms of my own experience. So it was a challenge, but I had plenty of people to go to as resources, and who could check out what I’d done and help make it better. And what’s interesting about the big model is that you can see my progression as we go around, and now of course I want to go back and do it all over again.  

So in terms of the challenges, I bought a Sony A7S camera and a Nauticam housing for it, and we just went in and started taking a bunch of photographs, came back, and put it into Agisoft. I have to say my expectations were low, but we were all pleasantly surprised when the model came back. This is like, “Wow that’s what we’re actually seeing there,” and it’s so cool. So that gave me the confidence to say, “I think I can do this,” and we basically picked about 250 m/817 ft of cave passage, which is a great example of the mining activity and of seeing what people were doing there. 

That sounds like quite a learning curve, and a big challenge. 

Meacham: Yes, we just started going in and piece by piece doing sections of the cave. I can’t remember how long in total we were down there. I’m sure it’s written down somewhere, but we took something around 18,000 photos. And as you know, taking the photos is probably the easiest part. Having the computing power and post-processing of the images is the key. A lot of people treat Agisoft as a bit of a black box, but you know it’s garbage in, garbage out. So in terms of the environment, we’re talking about a ceiling height that’s minimal, and while you can fit through OK, you want to be as high as possible for the photogrammetry in order to cover more area. 

“I’m sure it’s written down somewhere, but we took something around 18,000 photos. And as you know, taking the photos is probably the easiest part. Having the computing power and post-processing of the images is the key.”

So, we just worked section by section, using the line as a reference. I was going down the line and started by making sure that I got any markers on it, and then going back and forth to get all the photos. The person that suffered the most was whoever was assigned to dive with me, as they just had to sit there and watch me go back and forth while taking the photos.

18,000 images! That’s a whole lot of processing.

Sam Meacham: Yes, we’re lucky to have the guys at University of California at San Diego (UCSD) helping us with the processing. I probably started off taking too many photos, but the computer guys complimented us on the photos and the overlap and coverage. 

A landmark of piled stone and broken speleothems left 10,000-12,000 years ago by the earliest inhabitants of the Western hemisphere to find their way in and out of the mine. Photo courtesy of CINDAQ.

So what about other survey techniques, was there anything special about mapping this site?

Devos: We surveyed the first part of the cave, and that was pretty normal, but once we found the mine, then suddenly we had a need for all these new types of symbols that didn’t exist before for cave survey. I tried to think about what would be interesting to make notes of, but I didn’t want to speculate as to whether something was a natural pit or whether it was digging. 

The mine holds some of the best-preserved evidence of the earliest inhabitants of the hemisphere. Photo courtesy of CINDAQ

So we came up with three new symbols. There was already a symbol for a pit, but we added a jagged line on the pit to show that there was a broken edge, so it was smashed. Then we came up with a symbol for a displaced object, so if you see some stalactites and there was no way it came from the ceiling above, then that’s a displaced object. And then if you have stacked objects, so objects placed on top of each other, we had a symbol for that. We then made all of these colored red. I chose red because of the extracted material, the ochre. Also, when you look at the map, and you see all that red, it really shows the extent of the manipulation of the cave. It really brings it out, and I think that’s the most important thing about this cave. Sidewall information is nice, but this is very much an archaeological site.

So what’s next with the site? Any further diving plans?

Devos: We have some plans in place. The map that we’ve made, the photogrammetry, and the video documentation, even the exploration are not finished. So we actually concentrated on one area and tried to get that in the bag, you know, and focus our studies and our samples in that area, without stretching too far, but there’s still a huge portion to go. The technology really helps here, because you can bring that information out for the scientists and others to see. And then there’s much less need for others to go back there. 

And this is really the part where we don’t know what’s going to happen. Are divers one day going to be able to go there to tour this site? Luckily, I’m not the one who will be making that decision; there is an archaeological department in Mexico who set the rules. But these conversations are starting, and we’re not really sure where they will lead. But for now we are doing what we can to secure the documentation of the site and working closely with the archaeologists and the landowner. 

A CINDAQ diver noting details of the mine. Photo courtesy of CINDAQ.

So a last question: What would your advice be to a diver who is just starting out on their GUE journey, and who hears about this and other projects, and wants to one day join?

Devos: We have been running all kinds of projects down here for years: exploration, science, surveys. Come and get involved, and help out. Good basic training helps open up the door. 

Meacham: Once you’ve trained and gained enough experience to become confident in whatever environment you’re interested in, then come and get involved. There’s great training with the GUE Documentation Diver program, Science Diver, Photogrammetry Diver, and Cave Survey where you can actually put these skills to the test. Everyone on a project is an important part of making it work. Obviously it becomes tricky when archaeology is involved, as there can be federal laws and regulations that restrict access, and so we can’t always put just anyone onto a site, but there are all sorts of projects within GUE to help develop those skills and get known by project leaders.

Le Maillot: Of course, project diving is what GUE has been known for since the very beginning. So I think making that initial step to take training with GUE is an important one in the right direction. That’s the starting point of understanding how we are organized, the procedures that we use, [and] the team aspects of all our diving. And then it’s about thinking about what you want to do. 

“Of course, project diving is what GUE has been known for since the very beginning. So I think making that initial step to take training with GUE is an important one in the right direction.”

If you’re interested in wrecks, you have Mario Arena in Sicily or Richard Lundgren with the Mars project, and you’re naturally going to be headed down the Tech 1/CCR route. If it’s the stuff in Florida, or Bosnia, or here in Mexico, and the cave thing really rocks your boat, then that’s where the GUE cave training comes in. Then, as you progress with your tech or cave training, you will get to know divers who are involved in projects, and that could be your instructor. You know, if you come here to do some cave diving in Mexico, then Fred is going to mention a few things about survey and cave projects in Mexico and around the world. So that will start opening up a different perspective for you. 

Additional Resources:

InDepth: Data for Divers: Mexican Explorers Go Digital to Chart Riviera Maya

Watch a Video of the Mine on GUE.tv. (Requires a GUE.tv membership or signing up for a free trial)

For more information about the La Mina project, you can visit the CINDAQ website

Check out the CINDAQ YouTube channel


John Kendall is a GUE technical, cave, and CCR instructor living in the UK. Since he was a small child, John has been fascinated by the underwater environment and the possibilities of adventure, and he is grateful to GUE for helping him to turn those childhood dreams into reality. As an instructor, John regularly travels around the world teaching GUE classes and helping to build local GUE communities. For the last 5 years, John has been working with underwater 3D Photogrammetry as a technique for nautical archaeology. This cutting edge technique allows for digital 3D models to be created of shipwrecks and caves, and allows researchers and scientists unparalleled abilities to manipulate and navigate the sites from the comfort of their own computers. John was the primary author of the GUE Photogrammetry class. He is also a member of the GUE Training Council and a Fellow of the Explorers Club.

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