Poza del Caracol, Sistema Zacatón

Main characteristics

Coordinates: 22.9938 N -98.1638 W
No:109        (list of all attractions)
Category:Sinkholes, Lakes, bays and streams
Values:Geology, Biology
Address:North America, Mexico, Tamaulipas, southern part of the state, 12 km north-west from Aldama town
Depth:Full depth not reached, measured up to 114 m depth

One of the prominent features of the unique Sistema Zacatón is Poza del Caracol - small, very deep sinkhole which is not fully explored this far.

Sistema Zacatón

Sistema Zacatón is area with incredible characteristics unparalleled in the world. In total area contains some 20 unusual features - sinkholes, caves, springs created by deep groundwater heated by volcanic processes. Karstification processes here continue today as well - acidic groundwater continues to strip away the limestone and deposits it in unusual travertine formations.

Poza el Caracol

Poza del Caracol belongs to the central, most interesting group of these karst formations. Formation of this sinkhole continues up to this day - vertical cliffs around it often have landslides. El Caracol has not been fully investigated - it has been dived up to 114 m depth. It contains passage which leads in the direction of the neighbouring El Zacatón but most likely does not reach it.

Acidic water in this sinkhole has the highest level of dissolved hydrogen sulfide if compared with neighbouring sinkholes. Content of hydrogen sulfide fluctuated in the pool daily - this may be explained by microbial activity. Travertine walls here are entirely covered with purple, red and green biomats.

Temperature of water in El Caracol is 30° C, acidity - 6.9 pH. Water temperature in the sinkhole is remarkably similar to the temperature in nearby El Zacatón although both caves do not have direct connection.


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  1. Marcus Gary, Caracol, Sistema Zacatón, research homepage. Accessed on June 27, 2010

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