Sac actun underwater cave system


Heaven’s gate. One of the most popular places of the cenote Nohoch Nah Chich part of the Sac Aktun system. (photo: Álvaro Herrero. Mekanphotography).

Geological Period


Main geological interest

Geomorphology and active geological processes


Yucatán Peninsula / Quintana Roo State – Mexico.
20°14’47.0″N, 87°27’51.0″W

Heaven’s gate. One of the most popular places of the cenote Nohoch Nah Chich part of the Sac Aktun system. (photo: Álvaro Herrero. Mekanphotography).


The extensive cave systems under the Yucatan Peninsula have been a guardian of hidden and invaluable treasures to learn from our history. Remains of Pleistocene animals and humans that date from a time long before the occupation by the Mayan civilization have been found within submerged passages and galleries (de Azevedo et al., 2015). Being underwater, these caves provide a unique environment for the preservation of human and animal remains linked to a fascinating and unique geological and geomorphological history (Collins et al., 2015), and they provide evidence of the Holocene paleoclimate (van Hengstum et al., 2010).

The Blue Abyss is an underwater shaft of 71 m in depth part of the Sac Actun System. (Photo: Álvaro Herrero. Mekanphotography).

The Sac Actun cave is 368 km long, making it the longest underwater cave system in the world and the second longest cave in the world after Mammoth Cave in Kentucky, USA. This system is in the Yucatan Peninsula in Mexico and formed on a sedimentary platform of Mesozoic and Cenozoic rocks with a thickness of up to 3500 meters (Kambesis and Coke, 2016). The most extensive rocks belong to the Carrillo Puerto Formation with ages ranging from Miocene to Pliocene. They accumulated in a shallow marine environment affected by constant sea level variations with constant emersions and submersion as evidenced by at least three “caliches” levels recorded in situ (Collins et al., 2015). It is important to note that the Yucatan Platform has been stable since the Cretaceous, and the karst development is the result of the dynamics of the mixing zone (halocline). The mixing zone was affected by sea-level changes, which allow for paleoenvironmental interpretations (Gabriel et al., 2009). More than 7000 sinkholes (cenotes) exist in the Yucatan Peninsula. These are deep sinkholes, and most of them occur in the region of the Sac Actun System (Smart et al., 2016) (Kambesis and Coke IV, 2016).

The Sac Actun underwater cave system has been extensively studied for knowledge of its geology and karst geomorphology, the paleoclimatic and paleoenvironmental evolution of the Yucatan Peninsula, ecosystem services of the underground system, and preserved archives of archaeological, anthropological, and paleontological evidence of occupation in different periods.

Sac Actun system. Underwater cartography is a very slow, expensive, and risky work. Every year divers survey for new sections of the Sac Actun system, and the information is compiled by the Quintana Roo Speleological Survey in a volunteer effort.

De Azevedo, S. et al. (2015) ‘Ancient remains and the first peopling of the Americas: Reassessing the Hoyo Negro skull: Reassessing Affinities of the Hoyo Negro Skull’, American Journal of Physical Anthropology, 158(3), pp. 514–521.

Available at:

Collins, S.V. et al. (2015) ‘Reconstructing water level in Hoyo Negro, Quintana Roo, Mexico, implications for early Paleoamerican and faunal access’, Quaternary Science Reviews, 124, pp. 68–83. Available at:

Gabriel, J.J. et al. (2009) ‘Palaeoenvironmental evolution of Cenote Aktun Ha (Carwash) on the Yucatan Peninsula, Mexico and its response to Holocene sea-level rise’, Journal of Paleolimnology, 42(2), pp. 199–213. Available at:

Van Hengstum, P.J. et al. (2010) ‘Linkages between Holocene paleoclimate and paleohydrogeology preserved in a Yucatan underwater cave’, Quaternary Science Reviews, 29(19), pp. 2788–2798. Available at:

Kambesis, P.N. and Coke IV, J.G. (2016) ‘The Sac Actun System, Quintana Roo, Mexico’, Boletín geológico y minero, 127(1), pp. 177–192.

Smart, P.L. et al. (2006) ‘Cave development on the caribbean coast of the Yucatan Peninsula, Quintana Roo, Mexico’, Special Paper of the Geological Society of America, 404, pp. 105–128. Available at:

Rafael López Martínez
Institute of Geology, Universidad Nacional Autónoma de México

Ricardo Barragán Manzo
Institute of Geology, Universidad Nacional Autónoma de México

Emmaline M. Rosado-González
Department of Geology/Geosciences Centre (CGeo), Universidade de Trás-os-Montes e Alto Douro, Portugal