Summary
Highlights
The Yucatan Peninsula, despite its lush landscape and abundant rainfall, lacks major rivers. Instead, its water is hidden beneath the surface in a vast network of underground tunnels, an aquifer partly carved by a historical asteroid impact that has shaped life on the peninsula.
The Yucatan is comprised of a 1.5-kilometer thick block of limestone and carbonate rocks, formed from marine life over millions of years. Rainwater, made slightly acidic by dissolved carbon dioxide, slowly dissolves this limestone, creating a system of caves, tunnels, and an estimated 9,000 sinkholes called cenotes. This process creates a 'Karst' landscape, making the Yucatan one of Earth's largest Karst aquifers, where rain flows underground rather than forming rivers.
The asteroid impact 66 million years ago that caused the extinction of non-avian dinosaurs occurred in the Yucatan. While subsequent carbonate deposits filled the 200 km wide crater, fractures around the impact's edge created paths for water, forming a distinct ring of deep sinkholes that are visible from satellite images.
The underground caves of the Yucatan host unique life, including diverse microbes distinct from ocean samples, and specialized fauna like blind cavefish and shrimp found only in the region. Paleontologists have discovered prehistoric animal bones and human remains within these cenotes. The ancient Maya civilization built their cities near cenotes for water access and even excavated their own water storage pits, highlighting the long-standing importance of these natural features.
Karst aquifers are highly susceptible to pollution because water flows quickly through them, allowing contaminants to spread rapidly, and limestone does not filter water as effectively as other sediments. Rapid development in the Yucatan has led to significant contamination of the aquifer, with 92% of tested cenotes in 2021 showing pollution from sewage and pesticide runoff, emphasizing the fragility of this vital underground water source.