What is a cenote and how is it formed

A cenote, also called a sinkhole or known by the Mayans by the word “tz’onot”, which means “cavern with water” , is a very curious underground formation that draws the attention of most people.

We can say that, in a nutshell, a cenote is a body of underground water that is found deep in a cave or cavern and has been formed in a totally natural way. Another characteristic of the cenotes is that the water in these formations is close to the hole in the cave or cavern, so a certain amount of light enters , which facilitates the presence of vegetation and some animals.

To learn a little more about what cenotes and groundwater are themselves, we encourage you to read these other articles about What are groundwater and about underground rivers: what they are and how they are formed .

The formation of a cenote occurs in a totally natural way through the dilution processes of calcium carbonate rocks by the action of carbonic acid from the rains, in addition, the passage of the passing waters has a great influence on its formation. underground or underground . The rocks wear out and form vaults until the moment in which the roof of these becomes increasingly thin and ends up collapsing, leaving the flooded part totally or partially exposed.

Cenotes can be classified based on some characteristics and one another. Hall (1936) proposed a classification of the different types of cenotes according to their shape :

• Cenotes with a glass shape and a small opening.
• Cenotes with vertical walls, glass shape and large opening.
• Cenotes with sloping walls that reach a shallow pool.
• Cenotes cave with the presence of a side entrance that descends until it reaches a chamber with water inside.

However, the different types of cenotes can also be classified depending on their age :

• Open-air cenotes , the oldest being fully exposed.
• Semi-open cenotes , being those of intermediate age.
• Cenotes in grotto or underground , being the youngest as they still retain the roof.

Another classification may be the one carried out (Navarro-Mendoza et al. 1988) that divides the cenotes into two types, depending on their proximity to the coast :

• Cenotes located on the coastline , those that are between 100-2,000 meters, characterized by containing marine and fresh water mixed in a more or less homogeneous way, so that in the water column it is defined as brackish water. The fauna found in these cenotes has a great marine influence.
• Cenotes located between 3,000 and 8,000 meters from the coast , the water is fresh or slightly brackish, since, although they are further from the sea, the cracks they present allow the filtration of sea water, which is why a salty layer is formed under the fresh water layer.

Therefore, if we ask ourselves if a cenote is fresh or salt water, taking into account this previous classification, the reality is that they can be both fresh and salt water.

The flora and fauna of the cenotes is unique , since they are very different ecosystems from others that we know much more about (jungles, rivers, coasts, etc.).

Flora of the cenotes

Apart from some aquatic plants and algae, the flora of these depends on the distance to the coast. For example, in the cenotes closest to the coast there are mangroves, ferns and palms. However, in those further afield you can find plants such as coconut palms, guayas, chicle or sapodilla trees and cacao.

Fauna of the cenotes

In them you can find fish such as the blind eel, the blind white lady and the Mexican axolotl , three threatened and endangered species. Also in them you can see iguanas, frogs, turtles, butterflies and a variety of birds, such as swallows or Toh birds.

At the bottom of the cenotes we can find some aquatic plants and algae and some aquatic bottom animals , such as some species of fish and amphibians, as well as organic remains of the vegetation and fauna of the place (for example, remains of branches and leaves or remains of organic waste from animals).

Apart from this, pollution in the cenotes is also a reality and, in fact, at the bottom of many of them, residues of all kinds have already been found, such as food wrappers, plastic containers, cans, batteries, toys, nets. fishing, PET containers, among many others. Here you can learn more about the contamination of groundwater , since these include that of the cenotes.

Next, as examples of these underground formations, the names of the best known cenotes will be shown :

• Cenotes in Spain: the Pozo Azul and the Cenote de la Cueva del Moraig.
• Cenotes in Mexico: here we mention some cenotes in Cancun and other cenotes in the Riviera Maya, such as Cenote Chacmool, Siete Bocas, Cenote Tajma, Cenote Azul, Cenote Ponderosa and Cenote Aktun Chen.
• Cenotes in Yucatán: Cenote Ik-Kil, Cenote X-keken, Cenote Zací, Cenote Lu’um, Kankirixché, Chukumaltic, Cenote calavera, among others.

For the Mayan culture , that is, since ancient times, the cenotes have been of great importance. Not only because these were a great source of water , which is why the ancient Mayan cities settled near them, but also because they were considered as a symbol of duality , that is, they were considered as portals that allowed contact with the world of the dead.