La Pilita sinkhole, Sistema Zacatón

Coordinates:	22.9940 N -98.1587 W
No:	107        (list of all attractions)
Category:	Sinkholes
Values:	Geology, Biology
Rank:	8
Address:	North America, Mexico, Tamaulipas, southern part of the state, 12 km north-west from Aldama town
Alternate names:	Poza La Pilita
Depth:	< 120 m

Rising DEPTHX robot out of La Pilita. Travertine walls seen. Image by Marc Airhart, Wikipedia, public domain

This sinkhole is one of the most interesting features in the unique Sistema Zacatón karst field.

La Pilita sinkhole seems to be comparatively small - diameter of waterbody at the surface is just some 20 - 35 m. But this deep blue pool with slightly acidic water though is more than 120 metres deep!

Sinkhole in process of closing

At greater depth La Pilita becomes wider - at the depth of 45 m it is 120 m wide in north - south direction and 90 m wide in east - west direction.

It has not always been that - earlier La Pilita has been wide also at the surface level. This is testified by a wide travertine rim around the sinkhole. This plain travertine is covered with pleasant meadow.

Walls below the water level resemble the formations usually formed by hot mineralised springs. These walls are covered with bright red, pink and green microbial mats, often hanging down like stalactites.

Water in La Pilita is more than 31° C warm (the warmest of five central cenotes), it contains little dissolved oxygen. There is felt smell of rotten eggs around this sinkhole.

Map

See La Pilita sinkhole, Sistema Zacatón on the map of Mexico!

References

1. Marcus Gary, Sistema Zacatón, research homepage. Accessed in 23rd June 2010