Zacatón 2.2

Zacatón 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 339m: the 392m plus deep Pozzo del Merro is deeper, butUsing an autonomous robot, the underwater portion of Zacatón has been measured to be 319m deep . 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 three new phyla of bacteria.