Zacatón

Zacatón (El Zacatón sinkhole) is a thermal water filled sinkhole belonging to the Zacatón system - a group of unusual karst features located in Aldama Municipality near the Sierra de Tamaulipas in the northeastern state of Tamaulipas, Mexico. It is the deepest known water-filled sinkhole in the world with a total depth of 339 metres (1,112 ft): the 392 metres (1,286 ft) plus deep Pozzo del Merro (Sant'Angelo Romano, Latium Region, Italy) is deeper (actual depth yet unknown), but its nature as a near-vertical cave or a sinkhole still being debated.

Using an autonomous robot, the underwater portion of Zacatón has been measured to be 319 metres (1,047 ft) deep (a 20-metre (66 ft) difference between the rim of cliff and surface of water adds to the total depth). Zacatón is the only sinkhole of the five located in Rancho La Azufrosa to have any noticeable water flow.

The name Zacatón comes from the free-floating islands of zacate grass which move around on the surface with the wind.

Scrapings from the rock walls beneath the surface yielded at least 3 new phyla of bacteria.

El Zacatón's depth has made it an important dive site:

Zacatón is just one of the numerous sinkholes and other karst features in the region. Here are located more than 15 sinkholes, several cave systems and karst springs with caves. Several of these karst features have unusual characteristics like travertine lids over several of the sinkholes with isolated waterbodies below.

Since the late 1990s, Dr. Marcus Gary, a hydrogeologist at the Edwards Aquifer Authority and adjunct professor at the Jackson School of Geosciences, University of Texas at Austin has studied Sistema Zacatón to understand how the sinkholes formed and how they evolve over time. During these studies, Gary made extensive use of a number of investigative tools, including those on the DEPTHX probe, geophysics, isotope geochemistry, field mapping, and geomicrobiology. Gary was a primary member and co-PI on the DEPTHX mission, which used an autonomous underwater robot to explore the deepest parts of Zacatón for the first time.

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