How Were the Yucatan Cenotes Formed? The Geological Story Behind Mexico’s Underground World
Last updated: July 2026
The information in this article is based on the scientific knowledge available at the time of publication and may be updated as research on cenotes and the hydrogeology of the Yucatan Peninsula continues to evolve.
Diving into a cenote often feels like entering another world. Exceptionally clear water, stalactites hanging from the ceiling, underground rivers that seem to stretch endlessly into the darkness and, in some places, a mysterious halocline that suddenly blurs your vision.
But these extraordinary landscapes did not appear overnight.
The cenotes of the Yucatan Peninsula are the result of a geological history spanning tens of millions of years. Their formation is connected to the evolution of an ancient tropical sea, the slow dissolution of limestone by rainwater, major Ice Age periods and dramatic changes in global sea level.
Contrary to a widespread misconception, cenotes are not simply craters created by the Chicxulub asteroid impact.
Their origin is considerably more complex — and far more fascinating.
In this article, we will travel back through geological time to understand, step by step, how one of the world’s most extensive flooded cave environments developed and why the cenotes of the Yucatan are such an exceptional natural heritage today.
➜ New to cenotes? Read our complete guide: What Is a Cenote?
Table of Contents
- Before the cenotes: a tropical sea covered the Yucatan
- Limestone: a rock that slowly disappears drop by drop
- How water began carving the invisible underground landscape
- When the caves were completely dry
- How stalactites and stalagmites formed
- The end of the last Ice Age
- Why do cenotes contain both freshwater and saltwater?
- Why are some cenotes open to the sky?
- Did the Chicxulub asteroid create the cenotes?
- Why is Chicxulub so closely associated with cenotes?
- Are cenotes still forming today?
- Why is cenote water so incredibly clear?
- Why is every cenote different?
- Why is it essential to protect the cenotes?
Before the Cenotes: A Tropical Sea Covered the Yucatan
This is where the story really begins.
To understand how cenotes formed, we first need to forget the Mexico we know today.
Around 100 to 70 million years ago, during the Cretaceous Period, the Yucatan Peninsula did not exist in its present form. The region was covered by a warm, shallow tropical sea, comparable in some respects to the modern Bahamas.
This tropical sea supported an enormous diversity of marine organisms:
- corals;
- mollusks;
- foraminifera;
- calcareous algae;
- echinoderms;
- and many other organisms capable of producing calcium carbonate.
When these organisms died, their shells and skeletons slowly accumulated on the seafloor.
Year after year.
Millennium after millennium.
For millions of years.
The gradual accumulation of carbonate sediments eventually produced layers hundreds of meters thick.
Under the weight of successive deposits, these sediments were compacted and cemented together, eventually becoming a rock every cenote diver knows, even if they do not always realize it:
limestone.
Even today, almost the entire Yucatan Peninsula rests upon this enormous limestone platform.
This geological characteristic is fundamental because limestone possesses a property that would eventually shape the entire landscape:
it can slowly be dissolved by naturally slightly acidic water.
Without this particular rock, the cenotes simply would not exist.
💡 Did You Know?
The limestone underlying almost the entire Yucatan Peninsula was largely formed from the shells and skeletons of billions of marine organisms that lived in an ancient tropical sea tens of millions of years ago.
In other words, today’s cenote divers are exploring rock that is largely biological in origin.
Limestone: A Rock That Slowly Disappears, Drop by Drop
At first glance, limestone appears extremely solid.
Limestone cliffs, plateaus and fossilized reefs can give the impression of an almost indestructible material.
But over geological timescales, limestone is surprisingly vulnerable.
Its defining characteristic is that it is slightly soluble in naturally acidic water.
This property is responsible for many of the world’s great karst landscapes: the caves of Slovenia, the dramatic limestone formations of southern China, parts of the Balkans — and, of course, the cenotes of the Yucatan.
But where does that acidity come from?
Rainwater is not chemically pure.
As it passes through the atmosphere, it naturally absorbs carbon dioxide (CO₂). Once it enters the soil, it absorbs even more CO₂ produced by plant roots, fungi and microorganisms living within the upper layers of the ground.
The dissolved carbon dioxide reacts with water to form a small amount of carbonic acid (H₂CO₃).
This is not a powerful acid.
But it is strong enough to slowly attack the calcium carbonate that makes up limestone.
With every rainfall, an almost imperceptible quantity of rock is dissolved.
A fracture widens by a few micrometers.
Then a few millimeters.
Then a few centimeters.
Over millions of years, this almost invisible process can transform a solid limestone platform into an enormous underground labyrinth.
It is a remarkable example of geological power: an extremely slow process capable of reshaping an entire landscape.
This gradual dissolution process is called karstification.
Without karstification, there would be no caves, no underground rivers and no cenotes.
💡 Did You Know?
Unlike many other regions of the world, the Yucatan Peninsula has almost no permanent surface rivers.
Most rainwater infiltrates directly into the limestone and circulates underground through an enormous karst aquifer.
How Water Began Carving the Invisible Underground Landscape
Once the first fractures developed, a self-reinforcing process began.
The wider a fracture became, the more water could pass through it.
And the more water circulated through the fracture, the more limestone it could dissolve.
This positive feedback loop gradually accelerated the development of underground passages.
At first, there were only tiny fractures invisible to the eye.
Then small conduits appeared.
Those conduits became passages.
Eventually, some developed into extensive underground waterways.
Over hundreds of thousands of years, these networks became increasingly complex. Some passages connected with others, some divided into separate branches, some collapsed, while others continued to expand.
This is how a karst aquifer develops: an enormous natural reservoir in which groundwater circulates through a complex network of fractures, passages and cavities.
Today, beneath the Yucatan Peninsula, these underground networks extend for thousands of kilometers.
Cave explorers have already mapped several of the longest known flooded cave systems on Earth, including Sistema Sac Actun and Sistema Ox Bel Ha, while many passages and potential connections remain unexplored.
Unlike a surface river, groundwater moves through this environment according to gravity, limestone permeability and pressure differences between the interior of the peninsula and the Caribbean coast.
For a cave diver, every guideline therefore follows pathways that water has been shaping for hundreds of thousands — and in some cases millions — of years.
More than 1,500 kilometers of underwater passages have already been explored beneath the Yucatan Peninsula, and new connections continue to be discovered.
➜ Discover the Yucatan’s cenotes in our complete cenote guide.
When the Caves Were Completely Dry
This is probably one of the most surprising chapters in the history of the cenotes.
Today, divers swim through completely flooded passages surrounded by crystal-clear water.
Yet during significant periods of their history, many of these caves were dry.
To understand how this happened, we need to look back at the major glacial periods of the Quaternary.
During the past 2.6 million years, Earth’s climate has alternated between cold glacial periods and warmer interglacial periods.
During the coldest phases, enormous ice sheets covered large areas of North America, Europe and Asia.
All of that ice represented an enormous volume of water removed from the oceans.
As a consequence, global sea levels fell dramatically.
At the Last Glacial Maximum, around 20,000 years ago, average sea level was approximately 120 to 130 meters lower than today.
This enormous drop profoundly affected the Yucatan Peninsula.
As sea level fell, the groundwater table also dropped, leaving extensive sections of the underground cave systems completely exposed to air.
The passages explored by divers today were once dry caves, containing air and receiving only limited water infiltration from the surface.
💡 Did You Know?
If a diver had visited some of these passages 20,000 years ago, they could have explored them on foot.
At that time, sea level was approximately 120 to 130 meters lower than today, and extensive sections of the Yucatan’s underground cave systems were dry.
This was also when another remarkable process transformed the caves.
Instead of limestone being dissolved, new mineral formations began to grow.
How Stalactites and Stalagmites Formed
When rainwater passes through the soil, it dissolves a small amount of limestone before entering a cave.
Once the water reaches an air-filled cavity, conditions change.
Some of the dissolved carbon dioxide gradually escapes into the cave atmosphere.
This change in chemical equilibrium causes calcium carbonate to precipitate.
In other words, limestone dissolved higher above the cave is slowly deposited again.
Drop by drop.
Over thousands of years.
Each drop leaves behind an almost microscopic layer of calcite.
On the ceiling, these deposits gradually form stalactites.
On the floor, falling drops build stalagmites.
When the two eventually meet, they form a column.
Many other formations can also develop: draperies, soda straws, rimstone pools, crystals and a remarkable diversity of speleothems recording the extremely slow evolution of the cave.
Most of these formations grow at an almost imperceptible rate.
Depending on local conditions, growth may range from fractions of a millimeter to several millimeters per year.
Some of the formations admired in the Yucatan’s cenotes today therefore required tens of thousands of years to reach their present size.
That is precisely why they represent such an exceptional geological heritage.
A stalactite broken by a single fin kick may represent the destruction of thousands of years of natural growth.
For divers, this is an important reminder of why excellent buoyancy and careful positioning are essential.
Every movement matters.
💡 Did You Know?
A large stalactite may represent tens of thousands of years of growth.
A single careless fin kick can permanently break it.
This is one reason excellent buoyancy control is so important when diving in cenotes.
➜ Want to experience these formations responsibly? Discover cenote diving in Mexico with Halocline Explorers.
The End of the Last Ice Age: When the Caves Slowly Flooded
No glacial period lasts forever.
Around 20,000 years ago, Earth’s climate began gradually warming.
The enormous ice sheets covering parts of the Northern Hemisphere began to melt, returning vast quantities of water to the oceans.
This transformation did not happen over a few decades.
It unfolded over thousands of years.
As global oceans rose, sea level in the Caribbean also increased.
Because the Yucatan aquifer is connected to the sea, the groundwater table gradually rose as well.
Passages that had previously been dry began to fill with water.
The deepest sections flooded first.
Then intermediate passages.
Eventually, large parts of the underground cave network became completely submerged.
The process was extremely slow.
Over the course of a human lifetime, the change would have been almost imperceptible.
But across thousands of years, an enormous underground landscape gradually transitioned from an air-filled environment into an aquatic one.
The stalactites, stalagmites and columns that had formed during periods when the caves were dry became submerged.
This is why divers can now see beautifully preserved cave formations beneath many meters of water.
They are silent evidence of a time when these passages were completely dry.
Why Do Cenotes Contain Both Freshwater and Saltwater?
This is one of the most remarkable characteristics of the Yucatan cenotes.
Many visitors imagine these caves are filled exclusively with rainwater.
The reality is considerably more interesting.
The Yucatan Peninsula behaves like an enormous limestone sponge.
Every year, tropical rainfall rapidly infiltrates the porous ground.
Unlike many other parts of the world, there are very few permanent surface rivers.
Most freshwater circulates underground.
This groundwater slowly flows toward the Caribbean Sea.
But underground, it also encounters saltwater associated with the ocean.
Because saltwater is denser than freshwater, it naturally occupies the deeper portions of the coastal aquifer.
The less dense freshwater remains above it.
These two water masses are not separated by a perfectly sharp boundary.
Instead, they create a transition zone known as a halocline, where salinity changes progressively with depth.
Depending on local conditions, this transition can range from a relatively thin layer to several meters thick.
When a diver passes through the halocline, differences in density and refractive index produce a spectacular visual effect.
The surrounding cave suddenly appears blurred, distorted or shimmering, almost like looking through intense heat.
The effect is not caused by dirty water.
It is the result of light passing through waters with different physical properties.
The halocline is one of the most distinctive underwater phenomena found in the cenotes of the Yucatan.
💡 Did You Know?
The blurred appearance of a halocline is not caused by poor water quality.
It results from differences in refractive index between freshwater and saltwater, which alter the path of light as the diver passes through the transition zone.
➜ Discover cenote dives where you can experience some of the Yucatan’s remarkable haloclines.
Why Are Some Cenotes Open to the Sky?
Looking at a cenote from the surface, it can resemble a natural lake.
In reality, many of the cenotes visible today are associated with something much more dramatic:
the partial collapse of an underground cave ceiling.
Over hundreds of thousands of years, some underground cavities continued to expand.
As passages grew larger, sections of their ceilings gradually became less stable.
When a ceiling could no longer support the rock above it, part of it collapsed.
This created a natural opening into the underground cave and aquifer.
The word cenote comes from the Maya term dz’onot.
Not all cenotes look the same, however.
Some are almost completely open, resembling circular wells filled with sunlight.
Others have only a small opening leading into a much larger underground system.
And many caves remain completely enclosed, accessible only through underground or submerged passages.
This diversity represents different stages and forms in the evolution of karst systems.
The cenotes we explore today are therefore snapshots of a geological story that is still continuing.
➜ Every cenote has its own geology and atmosphere. Explore our detailed guide to the Yucatan’s cenotes.
Did the Chicxulub Asteroid Create the Cenotes?
This is probably one of the most frequently asked questions about the cenotes of the Yucatan.
The short answer is:
No.
Cenotes are not impact craters left by the asteroid.
But the complete story is much more interesting.
Around 66 million years ago, an asteroid approximately 10 kilometers in diameter struck Earth near what is now Chicxulub Puerto in the northwestern Yucatan Peninsula.
The energy released was enormous.
The impact produced a crater approximately 180 kilometers in diameter and triggered catastrophic environmental effects.
The event is considered one of the principal causes of the extinction of the non-avian dinosaurs and approximately 75% of species living at the time.
It is sometimes claimed that the cenotes visible today were directly created by this impact.
That interpretation is incorrect.
The cenotes developed much later through the progressive dissolution of limestone, the formation of karst cave systems and the localized collapse of underground cavities.
In other words:
cenotes are not asteroid impact craters.
➜ Want to explore these remarkable landscapes? Discover our cenote diving experiences in the Yucatan.
Why Is Chicxulub So Closely Associated With Cenotes?
If the asteroid did not create the cenotes directly, why is Chicxulub so frequently mentioned when discussing them?
Because geologists have identified a much subtler relationship.
The impact profoundly fractured the regional geology.
These structural changes affected groundwater circulation and created zones where limestone could later be more susceptible to dissolution.
Tens of millions of years later, some of these weaknesses influenced the development of karst features.
The best-known example is the Ring of Cenotes, or Anillo de Cenotes.
Viewed on a regional map, numerous cenotes form a broad semicircular to circular pattern around the buried Chicxulub impact structure.
This distribution has fascinated scientists for decades.
Research suggests that geological structures associated with the impact influenced groundwater circulation and subsequent limestone dissolution.
So the asteroid did not directly excavate the cenotes.
Instead, the Chicxulub impact altered the geological structure of the region in ways that later influenced where some cenotes developed.
That distinction is essential.
Saying:
“The asteroid created the cenotes”
is scientifically misleading.
A more accurate explanation is:
“The Chicxulub impact influenced the geological structure and groundwater pathways that later affected the distribution of some cenotes.”
This distinction reveals just how complex the geological history of the Yucatan really is.
💡 Did You Know?
The Ring of Cenotes forms a remarkable pattern around the buried Chicxulub impact structure.
Its distribution helped scientists investigate the relationship between the impact crater, regional geology and groundwater circulation.
Are Cenotes Still Forming Today?
When looking at a cenote, it is easy to imagine a landscape frozen in time.
But geologically, nothing is truly static.
Every rainfall brings more water into the limestone.
Every infiltration continues — at an almost imperceptible scale — the processes that began millions of years ago.
Some fractures continue to widen.
Cavities continue to evolve.
Existing passages can change.
And in some areas, sections of cave ceiling may eventually collapse.
Such events are rare on a human timescale.
But over tens or hundreds of thousands of years, they gradually reshape the landscape.
Cave formations can also continue growing in air-filled sections where the appropriate chemical conditions remain present.
By contrast, formations that are permanently submerged no longer grow as active aerial stalactites and stalagmites because the necessary conditions are absent.
The cenotes we see today therefore represent only one stage in a geological evolution that continues.
They are not static monuments.
They are part of an active natural system.
Why Is Cenote Water So Incredibly Clear?
One of the first things divers notice when entering a cenote is the extraordinary clarity of the water.
At some sites, visibility extends for many tens of meters. A diver far in the distance can sometimes appear almost as if they were suspended in air.
This transparency is closely connected to the geological and hydrological environment.
Rainwater infiltrates the highly permeable limestone and travels through the underground system.
During this journey, suspended material can be filtered or settle out, contributing to remarkably clear groundwater.
There is another important factor.
Unlike exposed surface lakes and rivers, many underground passages are protected from wind and waves.
Sediments are therefore not constantly disturbed and resuspended.
Sunlight also reaches the cave environment only through natural openings.
Limited disturbance and relatively low concentrations of suspended material can produce exceptional underwater visibility.
Of course, conditions are not identical everywhere.
Heavy rainfall can temporarily affect visibility in some cenotes. Nearby construction, heavy visitation or poor diver buoyancy can also disturb sediments.
But under normal conditions, the Yucatan cenotes can offer extraordinary underwater visibility.
➜ Discover why Mexico’s cenotes offer some of the world’s most spectacular diving.
Why Is Every Cenote Different?
At first glance, it might be tempting to think that all cenotes are similar.
They are not.
Their diversity reflects their individual geological histories.
Every underground network developed according to different fractures, groundwater pathways and rates of limestone dissolution.
Some cavities remained relatively small.
Others developed into enormous underground chambers.
In some places, large sections of ceiling collapsed, allowing abundant sunlight to penetrate.
Elsewhere, only a small opening illuminates an extensive cave.
Depth also varies dramatically.
Some cenotes are only a few meters deep, while others descend for many tens of meters.
Their underwater phenomena also differ.
Some have spectacular haloclines.
Others are famous for natural hydrogen sulfide clouds.
Some stand out because of fossils, enormous chambers, dramatic light effects or exceptionally well-preserved cave formations.
Every cenote is therefore a unique combination of geology, hydrology and climatic history.
That diversity is precisely what makes the Yucatan Peninsula one of the world’s most extraordinary environments for divers and explorers.
➜ Explore our cenote guide to find the sites best suited to your diving level and interests.
Why Is Cenote Conservation So Important?
Once you understand how long these environments took to develop, the way you look at a cenote changes completely.
A cave passage may have taken hundreds of thousands of years to reach its current form.
A large stalactite may represent tens of thousands of years of growth.
Yet only a few seconds are needed to permanently damage this natural heritage.
One careless fin kick can break a formation that will not regrow within a human lifetime.
Poor buoyancy can disturb sediments that have remained undisturbed for generations.
Repeated contact with delicate formations can also accelerate their deterioration.
Protecting cenotes is therefore about much more than simply following diving rules.
It means recognizing that these landscapes preserve a history that began long before humans appeared.
For the duration of a dive, every diver becomes a visitor to an exceptional natural archive.
The best trace we can leave behind is often no trace at all.
💡 Did You Know?
Sistema Sac Actun and Sistema Ox Bel Ha, located in the Yucatan Peninsula, are among the longest explored underwater cave systems in the world.
Despite decades of exploration, new passages and connections continue to be discovered.
➜ Before your first dive, read our Cenote Diving FAQ.
A Journey Through Millions of Years
When diving into a cenote, it is easy to become captivated by the immediate beauty.
Sunbeams penetrating the water.
Silent passages.
Extraordinary light effects.
Almost unreal visibility.
Yet every one of these landscapes is the result of geological events that began more than one hundred million years ago.
A tropical sea deposited the sediments that eventually became limestone.
Rainwater slowly sculpted an immense network of underground caves.
Glacial periods allowed stalactites and stalagmites to develop inside dry passages.
Rising sea levels later flooded those caves, creating the underwater environments we explore today.
Even the Chicxulub impact 66 million years ago probably influenced the structure of the subsurface without directly creating the cenotes themselves.
Understanding this history profoundly changes the way we explore these places.
Every dive becomes much more than an underwater excursion.
It becomes a journey through time and through one of our planet’s most remarkable geological archives.
At Halocline Explorers, we believe discovering a cenote is not simply about admiring an extraordinary landscape.
It is also about understanding the millions of years that shaped it, so we can better respect and preserve it for future generations.
The next time you dive into a cenote, take a few seconds before descending.
In front of you is a landscape that took more than 100 million years of geological history to reach its present form.
Every passage tells the story of an ancient tropical sea.
Every stalactite records a time when these caves were dry.
Every beam of sunlight passes through a story far older than humanity.
Exploring a cenote is traveling through time.
Ready to Explore the Cenotes of the Yucatan?
Whether you are a newly certified diver or an experienced explorer, Halocline Explorers can introduce you to some of Mexico’s most remarkable cenotes in small groups, with safety, conservation and personalized guiding at the heart of the experience.
👉 Book your next cenote diving experience
👉 Discover our cenote diving in Playa del Carmen
👉 Explore our complete guide to the Yucatan cenotes
Timeline: How the Yucatan Cenotes Formed
| Period | Event | Consequence |
|---|---|---|
| ≈145–66 million years ago | A tropical sea covers the region. Marine organisms deposit carbonate-rich shells and skeletons on the seafloor. | Gradual formation of the enormous Yucatan limestone platform. |
| 66 million years ago | Chicxulub asteroid impact. | Regional fracturing of the subsurface. The impact did not directly create the cenotes but probably influenced groundwater circulation and the later distribution of the Ring of Cenotes. |
| 66 million years ago → present | Slightly acidic rainwater slowly dissolves limestone. | Progressive development of karst systems and underground caves. |
| 2.6 million years ago → 11,700 years ago | Repeated glacial cycles. | Sea level periodically falls, reaching approximately 120–130 m below today’s level during the Last Glacial Maximum. Extensive cave passages become dry. |
| During glacial periods | Dripping water deposits calcite inside air-filled caves. | Formation of stalactites, stalagmites, columns and other speleothems. |
| Since approximately 20,000 years ago | Natural warming following the Last Glacial Maximum. | Ice sheets melt and global sea level progressively rises. |
| Since approximately 11,700 years ago | Many cave passages become progressively flooded. | Development of the modern flooded cenote environment and freshwater/saltwater interfaces. |
| Today | Geological processes continue. | Limestone dissolution, cave evolution and occasional collapse continue to reshape the karst landscape. |
Glossary
Aquifer
A natural underground reservoir in which water is stored and moves through pores, fractures and cavities.
Calcite
A crystalline form of calcium carbonate commonly found in stalactites, stalagmites and other cave formations.
Limestone
A sedimentary rock composed mainly of calcium carbonate. Most of the Yucatan Peninsula is underlain by limestone.
Calcium Carbonate (CaCO₃)
The primary mineral component of many marine shells, corals and limestone.
Cenote
A natural opening providing access to groundwater or a flooded cave system. The word derives from the Maya term dz’onot.
Cave Formation
A general term for mineral deposits formed inside caves.
Sinkhole
A depression produced through limestone dissolution or collapse. Many cenotes are water-filled karst depressions or collapse features.
Meteoric Water
Water originating from precipitation such as rain.
Halocline
A transition zone where freshwater and saltwater meet, producing a salinity gradient.
Karst
A landscape shaped primarily by the dissolution of soluble rocks such as limestone.
Karstification
The processes through which water progressively dissolves limestone and develops fractures, cavities, caves and underground drainage networks.
Water Table
The upper surface of the saturated groundwater zone.
Porosity
The capacity of a rock to contain water within its pore spaces.
Quaternary
The geological period beginning approximately 2.58 million years ago, characterized by repeated glacial and interglacial cycles.
Speleology
The scientific study and exploration of caves.
Speleothem
The scientific term for mineral cave formations such as stalactites, stalagmites, columns, draperies and soda straws.
Stalactite
A mineral formation hanging from a cave ceiling.
Stalagmite
A mineral formation growing upward from a cave floor.
Column
A formation created when a stalactite and stalagmite join.
Mixing Zone
An area where freshwater and saltwater interact. In coastal aquifers, mixing can influence limestone dissolution and groundwater chemistry.
📌 Key Takeaways
If you remember only a few things about how the Yucatan cenotes formed, remember these:
✅ Cenotes are not craters created by the Chicxulub asteroid. They developed primarily through limestone dissolution and the collapse of underground cavities.
✅ The story began beneath a tropical sea. Marine organisms accumulated carbonate material over millions of years, contributing to the thick limestone platform underlying the Yucatan.
✅ Slightly acidic rainwater gradually dissolved the limestone, creating an enormous network of fractures, passages and caves.
✅ During major glacial periods, extensive sections of these caves were dry. Stalactites, stalagmites and other formations developed during these air-filled phases.
✅ Rising sea levels following the last glacial period progressively flooded many cave passages, producing the submerged environments explored today.
✅ The halocline results from the interaction between freshwater derived from rainfall and denser saltwater within the coastal aquifer.
✅ Cenotes continue to evolve. Limestone dissolution, groundwater circulation and occasional collapse continue to shape the landscape.
✅ Every cenote dive is a journey through more than 100 million years of geological history, making these environments one of Mexico’s most remarkable natural treasures.
Frequently Asked Questions
Are cenotes craters created by the Chicxulub asteroid?
No. Cenotes primarily result from limestone dissolution and the development and collapse of karst cavities. The Chicxulub impact probably influenced regional fracturing and the distribution of the Ring of Cenotes, but it did not directly excavate the cenotes.
How old are the cenotes?
The geological processes responsible for the Yucatan’s karst systems have operated over millions of years. The modern flooded configuration of many caves is closely associated with rising sea levels following the last glacial period.
Why are there so many cenotes in the Yucatan?
Because the peninsula consists largely of a thick, highly permeable limestone platform that favors karst development and underground drainage.
Why is cenote water so clear?
The underground hydrological environment, low levels of suspended particles and limited disturbance in many passages can produce exceptional water clarity.
Are all cenotes connected?
No. Many belong to interconnected cave systems, while others may be isolated or connected only through passages that are extremely small or have not yet been explored.
Why is there a halocline in some cenotes?
Because less dense freshwater overlies denser saltwater within the coastal aquifer, producing a transition zone where salinity changes with depth.
➜ Learn more: What Is a Halocline?
Why are there stalactites underwater?
Because they formed when the caves were air-filled and sea level was substantially lower than it is today.
Are cenotes still forming?
Yes. Limestone dissolution and other karst processes continue today.
Are all cenotes open to the sky?
No. Some are completely open, others partially open, while many caves remain enclosed underground.
Why are there almost no rivers on the surface of the Yucatan?
Because rainfall infiltrates rapidly through the permeable limestone and most drainage occurs underground.
Can divers damage cave formations?
Yes. A formation that is broken may represent thousands of years of growth and will not recover on a human timescale.
How many cenotes are there in the Yucatan?
Thousands have been documented, but the exact number remains unknown and new cavities continue to be identified.
Reference Bibliography
Geology and Karst
- Perry, E., Marín, L., McClain, J. & Velázquez, G. (1995). Ring of Cenotes (sinkholes), northwest Yucatán, Mexico: Its hydrogeologic characteristics and possible association with the Chicxulub impact crater. Geology, 23(1), 17–20.
- Perry, E., Velázquez-Olimán, G. & Socki, R. A. Hydrogeology of the Yucatán Peninsula. Cited as a general reference on Yucatan hydrogeology.
- Kevin O. Pope et al. Surficial Geology of the Chicxulub Impact Crater, Yucatán, Mexico. NASA / NTRS.
Institutions
- Government of the State of Yucatan — Cenotes y Grutas de Yucatán, scientific and heritage publications.
- UNESCO — Ring of Cenotes of Chicxulub Crater.
Further Reading
- Journal of Cave and Karst Studies — research on tropical karst, hydrogeology and water chemistry.
- INAH publications concerning karst systems, cenote archaeology and their cultural importance, referenced through the Government of Yucatan’s publications.
