Unexpected discovery of an underwater cave in Tulum provides insight into the environmental consequences of human activity

What was thought to be a sinkhole at a federal highway in Tulum is actually a cave with crystal-clear water and vestiges that date from the Pleistocene and the Holocene , 2.5 million years ago, connected with other ecosystems that are part of the second-largest network of underground rivers in the world that flow in the area, according to the Mayab Speleological Circle.

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In an interview with EL UNIVERSAL , biologist Roberto Rojo, head of the group of speleologists that is studying the site, explained that they named the cave as “Me lleva el Tren” in an explicit reference to the Mayan Train megaproject that will traverse the area.

“In Speleology , we name recently explored caves, as well as some of its sections. From inside, we were able to listen to the constant pass of vehicles above us, which made us think about the impact of the great [infrastructure] developments in the region.

“We agree that cases like this are a reminder of the complexity and fragility of karst environments. Anything that happens at the surface of the Yucatán Peninsula , from sewers to the streets, the garbage, and the constructions, among many other activities, including megaprojects , must consider the karst nature of the region,” said Rojo García.

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Also the director of the Playa del Carmen Planetarium , he said that they named the cave, as a joke, as “Me lleva el Tren” hoping it does not happen.

“As speleologists, we are highly concerned about the development of this megaproject . This reminded us that there must be all the necessary studies that consider the particular characteristics of nature , the soil, and the whole environment here and in the Peninsula.

Unexpected discovery of an underwater cave in Tulum provides insight into the environmental consequences of human activity

“As a matter of fact, we recommend reinforcing the area around the cave so as not to affect the natural flow of water and to consider this event [the collapse] could happen again. The cave must not be covered,” he stressed.

The cave cannot be filled in because it would represent an “ecocide,” he warned by pointing out this action is also forbidden by the current Regulations on Caves and Caverns at the Solidaridad municipality.

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The inspections

The Mayab Speleological Circle intervened to study the 20-meters-wide by 60-meters-long cavity as requested by the director of Environment and Climate Change of the Solidaridad municipality, Nancy Martín Tzuc , on June 13, when the structure collapsed.

At first, the local Civil Protection Direction said it was a sinkhole ; Rojo García says that they noticed it was an underground cave whose origin dates back to thousands of years ago, and whose roof collapsed.

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The discoveries

After several days of research, in charge of archeologist Ximena Chávez , biologist Yuritzi Espino , master in sciences Fermín Teuctzintli , and cave divers Michel Vázquez and Mónica Torres , the conclusion of the team of experts showed it was indeed an underwater cave whose roof partially collapsed.

“We mapped the cave, on that first day, for nearly five hours. The next day, we carried on with the inspection on the aquatic part of the cave and returned the next day to continue.

“What we found was a stable environment with blind organisms, crustaceans like shrimp and cochineals . The roof has fossil remains of pink snails and, in general, I can say that, due to the kind of coast rock, it must be over 10,000 years old, possibly 2.5 million years old , from the Pleistocene-Holocene period,” she said.

Due to the number of mollusks on the rook, they called it “Snail Sky:” they also found prints of brain corals.

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“There can be two species of blind fish of the Yucatán Peninsula, Typhliasina pearsei and Ophisternon infernale,” according to the experts.

They also found roots of over 16 jungle tree species , as well as 14 other plant species that can directly take water from the aquifer.

Unexpected discovery of an underwater cave in Tulum provides insight into the environmental consequences of human activity

The information about the age and kind of rocks comes from the director of the “Centinelas del Agua” organization , Alejandro López Tamayo , who said it corresponds to mollusk limestone rock from the Pleistocene-Holocene.

The cave contains brackish water , so it was recommended to perform studies to evaluate the impact of saline intrusion, the pumping of water, as well as of its quality for there are hotels in the area.

They even found seven deep foundations of the Catalunya Royal Tulum hotel that, for now, “do not represent a danger to the life and survival of the cave, although the use of water should be evaluated.”

Why did it collapse?

About the reasons for the collapse, Rojo García said that it could be related to a series of works for a neighborhood three months ago that left a mount of debris and pavement , so the weight could have undermined the weak karst floor.

The area is already affected by the construction of the road , in addition to the recent tropical storm “Cristóbal,” that could have further undermined the structure due to the weight of water, but he clarified that there should be further studies to have more certainty on that regard.

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In the report, delivered to the municipal officer, the experts explained the soil at the entire Yucatan Peninsula is made of karst , that is, it is highly porous, of carbonate rock that, with time and the interaction of meteorological conditions, such as the water, the air, and the dynamic of tectonic platers, has caused the creation of cenotes – semi-flooded cavities -, faults , fractures , caverns , or caves .

“The Yucatán Peninsula has a 1000 meters deep calcium carbonate platform, thanks to which we have the only source of freshwater available in the region, best known as an aquifer .

“This calcium carbonate rock stores groundwater that allows the development of the region’s activities and grants the ecological flow required for ecosystems that depend on groundwater,” it says.

This groundwater connected throughout the peninsula, goes from the continental area to the coast, connecting jungles with reefs through groundwater discharge in the coastal areas and, in the case of Quintana Roo , in the Caribbean .

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