The Yucatán Peninsula, renowned for its extensive network of caves and cenotes, owes these geological features to a combination of ancient marine deposition, the profound impact of a cosmic event, and chemical dissolution.

Limestone Formation

Over millions of years, the Yucatán Peninsula was submerged under a shallow sea. During this period, marine organisms (so-called foraminifera, corals, and mollusks) accumulated on the seafloor, forming thick layers of limestone. This limestone, composed primarily of calcium carbonate, became the bedrock upon which the region’s karst landscape developed, and drilling studies showed that it is in some areas up to 2.5 km thick.

The Chicxulub Meteor

At the end of the Cretaceous period, about 65 million years ago, an asteroid approximately 10 kilometers in diameter struck the Yucatán Peninsula and was named after a town near it: Chicxulub (Yucatec-Maya, pronounced: “Tsheekshulub”). This impact released energy equivalent to billions of atomic bombs, creating a crater over 150 kilometers in diameter and reshaping the geological landscape.

The Chicxulub impact fractured the underlying limestone, creating zones of weakness. These fractures influenced the subsequent dissolution processes, leading to the formation of cenotes and cave systems. Many typical cenotes can be found within a distance of 83 km from the center in a concentric way, like pearls on a necklace, the so-called ring of cenotes. Also, as a result of the impact, a huge amount of dust was in the air, leading to extreme climate change and loss of vegetation that resulted in the extinction of many plant-eating animals, the dinosaurs and their dinosaur predators. 

Karstification: The Dissolution Process

Over millions of years, rainwater, slightly acidic due to increased carbon dioxide within, seeped into the ground, initiating the dissolution of the limestone. This process, known as karstification, led to the development of an extensive network of underground rivers and caves. When sections of these subterranean chambers collapsed, they formed cenotes, natural openings to the aquifer. Due to the marine history of the stone, there are many marine fossils to be found in the walls of the caves. But there is another interconnection between various factors that favoured the creation of the caves: the sea level had to be much lower than today, so that, on the one hand, there was a flow of fresh water towards the ocean, dissolving the limestone much faster. The seeping of the water was made possible and the stalactites and stalagmites formed in the shallower then dry caves by a constant dripping. These speleothems can today be found primarily in the shallow parts of caves, as they lay dry over a longer period of time, and deeper sections at the same time were submerged longer again and the flowstone formations may have dissolved again.

The impact area was at that time still a shallow ocean, where, thanks to coral growth and depositions (of so-called foraminifera), a limestone layer has formed that measures in some areas over 2.5 km of thickness. When the meteor hit the ground, it also broke the limestone plateau open, fracturing it in a star-like way away from the impact crater of the meteor. As a result of the huge amount of dust in the air, there was extreme climate change with loss of vegetation, leading to the extinction of plant-eating animals, and thereafter the extinction of their predators.

Also, precipitation mixed with CO2 and formed so-called acid rain and slowly penetrated the limestone and dissolved the soft stone so that channels and subterranean water systems formed over a long period of time. Due to the marine history of the stone, there are many marine fossils to be found in the walls of the caves. But there is another interconnection between various factors that favoured the creation of the caves: the sea level had to be much lower than today, that on the one side, there was a flow of fresh water towards the ocean dissolving much faster the limestone and the seeping of the water was possible and therefore forming the stalactites and stalagmites by a constant dripping in these formerly dry caves. These speleothems can be found primarily in the shallow parts of the cave as they lay dry over a longer period of time.

This unique combination of factors created the Underworld Cave Systems of the Yucatan Peninsula, and many of the world’s longest cave systems are found in the Riviera Maya.

Cenotes

The actual Cenote (derived from the Maya “ts’ono’ot” or “dzonot” meaning “well with water” or “cavern with water“) is the collapse of the roof that became too thin through erosion or was not supported by water anymore. Different cenotes have completely different characteristics, as we can find small holes or huge craters. As well as the innerspace of the cave system can have tight passages and huge rooms.

Where water meets stone, the Maya imagined Xibalba. Come and explore these hidden worlds and see for yourself.