The combination of geologic events, climatic change and the impact of a large asteroid have lead to the development of an incredibly unique and important ecosystem in Mexico's Yucatan Peninsula. The systems of underground rivers and cenotes are only just beginning to be studied but already they are showing that they play an important role in the transport of fresh water from the inland jungle to the Caribbean Sea. If one were to drive from Cancun to Belize not one bridge would be crossed. There are no superficial rivers or streams at all in the area. All the water within the peninsula is transported through the intricate cave systems that crisscross the peninsula. At this point in time we estimate that close to 350 miles of underground caves have been explored in the area between Playa del Carmen and Tulum. Although that may sound like quite a lot there is still quite some work to be done. We hope that the following summaries will help you better understand how the underground rivers were formed.
Solution Caves are able to form because certain conditions allow it. Limestone, which comprises much of the bedrock of the Yucatan Peninsula is an essential ingredient. Rain water, as it falls from the sky, mixes with carbon dioxide to form a weak solution called carbonic acid. As this concoction seeks the water table below the surface, it dissolves the limestone. Over the course of many thousands of years the caves are formed. The same beautiful decorations that one might encounter in a dry cave such as stalactites, stalagmites, columns and halactites are all present here in the Yucatan Peninsula.
"Glaciers on the Yucatan Peninsula?", you ask. Well, not really, but the last Ice Age did have an impact on the Yucatan Peninsula. During the last Ice Age, water levels of the world's oceans were on average 100 meters or 300 feet lower than their present day levels. If you sit back and think about that for a minute you can immediately see that the caves that we are presently diving were all dry during that period. When the Ice Age came to a close some 10,000 to 12,000 years ago, the climate of the planet warmed up, the glaciers receded and the caves were flooded. Scientists have varying views on how fast the water levels rose back up but most agree that it reached its current level around 1,000 years ago. Carbon dating of artifacts found in some area caves shows them to be 7,000 years old.
An added attraction the area is the Chicxulub (pronounced chick-chi-lube) crater. For many years scientists had theorized that a cataclysmic event in the earths history had caused dramatic climactic changes that led to the extinction of the dinosaurs. Recently evidence was found to support that theory in the beach village of Chicxulub located just north of Merida, Yucatan. Scientists have discovered that a large meteor impacted there 65 million years ago, and that the impact threw enough dust into the air to change the earths climate. To support this theory, information gathered from a NASA LandSat Thematic Mapper found a ring of cenotes 170 kilometers in diameter that mimics the edge of the impact crater. If you look at a map of the area such as Kevin Healy's Travel Map of the Yucatan Peninsula which is available in most US bookstores, you will see this ring circling Merida. A large scale investigation of the meteor was recently launched by the government of Yucatan, it will be interesting to see how much that impact affected the subsequent development of the caves.
The present condition of the caves from a geological point of view is for the most part pretty stable. There are some caves which have experienced collapses in the last ten to twenty years, but nothing on a large scale. The real threat to this unique and delicate ecosystem is as always, you guessed it, MAN. Rapid development of the coast of Quintana Roo combined with very lax environmental laws has set the stage for the caves to be impacted in a not so positive way. Sewage for most of the area is pumped into deep wells as is runoff. Dumps are built with no lining and contamination seeps through the porous limestone to the water table. Divers also have impacted many of the caves that seemed pristine not so many years ago. Of course the best thing to do is to leave the caves alone and let nature run its course, unfortunately reality tells us otherwise.
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© G.E.O. Grupo de Exploración Ox Bel Ha
Dedicated to the continued exploration of the world's largest underwater cave system.
Cave diving in cenotes and underground rivers in the Yucatan Peninsula,
Mayan Riviera, Quintana Roo, Tulum, Playa del Carmen, Mexico