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Sistema Sac Actun
Sistema Sac ActunLocation in Mexico
Location	Tulum Municipality, Quintana Roo, Mexico
Coordinates	20°14′47.6″N 87°27′50.8″W / 20.246556°N 87.464111°W / 20.246556; -87.464111
Depth	119.2 meters (391 ft)
Length	Underwater: 378.56 km (235.23 mi) Total: 386.122 km (239.925 mi)
Discovery	November 26, 1987
Geology	Limestone
Entrances	228 Cenotes
Difficulty	Advanced cave diving

Sistema Sac Actun (Yucatec Maya: sak aktun, lit. 'white cave', Spanish: sistema, lit. 'system') is an underwater cave system situated along the Caribbean coast of the Yucatán Peninsula with passages to the north and west of the city of Tulum. Discovery of a connection to Sistema Dos Ojos in 2018 made it the longest known underwater cave system. As of January 2023, it is the second longest underwater cave system in the world, only surpassed by Sistema Ox Bel Ha.

The remains of a mastodon and a human female that might be the oldest evidence of human habitation in the Americas have been found in the cave.

History of exploration

Exploration started from Gran Cenote 5 kilometers (3.1 mi) west of Tulum. The whole of the explored cave system lies within the Municipality of Tulum, in the state of Quintana Roo.

In early 2007, the underwater cave Sistema Nohoch Nah Chich was connected into and subsumed into Sac Actun making it the longest surveyed underwater cave system in the world. Sac Actun measured 230.8 km (143.4 mi) (after connecting with Sistema Aktun Hu (34 km (21 mi)(in January 2011) and is, as of January 2023 with an explored length of 259.5 kilometers (161.2 mi), only surpassed by the Sistema Ox Bel Ha at 435.8 kilometers (270.8 mi). Since early 2007, these two caves have frequently exchanged the title of world's longest underwater cave. Including connected dry caves makes Sistema Sac Actun 386.122 km (239.925 mi) long, the second longest cave in Mexico and third longest worldwide.

On December 9, 2004, after a dive with two other teammates, Kent Hirsch and Michael Nast were drowned deep in the cave as they got lost and have exhausted their oxygen supply.

In 2018, the discovery of a link between the Sac Actun system (reported to be 263 km (163 mi) long) and the Dos Ojos system in Tulum, Quintana Roo (84 km (52 mi) long) was reported. The connection was found by the Gran Maya Aquifer Project (GAM), led by the cave diver and explorer Robbie Schmittner. The combined system is reported to be the world's second longest underwater cave system known.

Upper Paleolithic remains

In March 2008, three members of the Proyecto Espeleológico de Tulum and Global Underwater Explorers dive team, Alex Alvarez, Franco Attolini, and Alberto Nava, explored a section of Sistema Aktun Hu known as the Hoyo Negro pit. At a depth of 60 meters (200 ft) the divers located the remains of a mastodon, as well as a human skull at 43 meters (141 ft) that might be the oldest evidence of human habitation in the Americas. Additional bones were located and the skeleton was later identified as that of a teenage female now referred to as Naia.

See also

• Eve of Naharon – Hominin fossil
• List of caves
• List of caves in Mexico
• List of sinkholes of Mexico – Links to Misplaced Pages articles on sinkholes, blue holes, dolines, cenotes, and pit caves
• Paleo-Indians – Classification term given to the first peoples who entered the American continents
• Settlement of the Americas – Prehistoric migration from Asia to the AmericasPages displaying short descriptions of redirect targets
• Speleology – Science of cave and karst systems

References

1. ^ "List of Long Underwater Caves in Quintana Roo Mexico". Quintana Roo Speleological Survey. National Speleological Society (NSS). January 10, 2023. Retrieved 10 January 2023.
2. ^ "Dry Caves and Sumps of Quintana Roo Mexico". Quintana Roo Speleological Survey. National Speleological Society. January 10, 2023. Retrieved 10 January 2023.
3. John Roach (March 5, 2007). "World's Longest Underground River Discovered in Mexico". National Geographic News. National Geographic. Archived from the original on March 11, 2007. Retrieved January 14, 2011.
4. "CINDAQ 2022 Annual report". CINDAQ. El Centro Investigador del Sistema Acuífero de Quintana Roo A.C.(CINDAQ). January 26, 2023. Retrieved February 3, 2023.
5. Michael Poucher, Bob Gulden (March 21, 2017). "World longest underwater caves". Geo2 Committee on Long and Deep Caves. NSS. Archived from the original on June 2, 2011. Retrieved May 26, 2017.
6. Bob Gulden (January 22, 2020). "Worlds longest caves". Geo2 Committee on Long and Deep Caves. NSS. Archived from the original on May 15, 2006. Retrieved March 24, 2020.
7. Jeff Burns, Pat Seiser (May 2007). "American Caving Accidents 2004 – 2005 (9 December Sac Actun, Yucatan, Mexico two fatalities, lost, out of air)" (PDF). Geo2 Committee on Long and Deep Caves. NSS. Retrieved Jun 20, 2024.
8. "Underwater cave is the world’s biggest", Mexico Daily News, January 15, 2018, https://mexiconewsdaily.com/news/underwater-cave-is-worlds-biggest/ (accessed 2018-01-17).
9. "World's Largest Underwater Cave Discovered". National Geographic News. 2018-01-17. Archived from the original on August 4, 2019. Retrieved 2020-05-11.
10. "Cave Archeology of Early Americans" (PDF). News from the Field. El Centro Investigador del Sistema Aquífero de Quintana Roo: 6. Winter 2011. Archived from the original (PDF) on 2015-02-06. Retrieved October 10, 2013.
11. ^ Fabio Esteban Amador (February 18, 2011). "Skull in Underwater Cave May Be Earliest Trace of First Americans". National Geographic. Archived from the original on April 26, 2021. Retrieved April 23, 2021.
12. Hodges, Glen (2014-05-14). "Most Complete Ice Age Skeleton Helps Solve Mystery of First Americans". National Geographic. Archived from the original on May 16, 2014.

• Steve Gerrard (2000). The Cenotes of the Riviera Maya. ISBN 0-9677412-0-3. online Version. Retrieved January 14, 2011.

v t e State of Quintana Roo
Chetumal (capital)
Municipalities (seats)	Bacalar (Bacalar) Benito Juárez (Cancún) Cozumel (San Miguel de Cozumel) Felipe Carrillo Puerto (Felipe Carrillo Puerto) Isla Mujeres (Isla Mujeres) José María Morelos (José María Morelos) Lázaro Cárdenas (Kantunilkín) Othón P. Blanco (Chetumal) Puerto Morelos (Puerto Morelos) Solidaridad (Playa del Carmen) Tulum (Tulum)
Places of interest	Caves Sistema Dos Ojos Sistema Nohoch Nah Chich Sistema Ox Bel Ha Sistema Sac Actun Islands Isla Contoy Isla Holbox Isla Mujeres Maya sites Chacchoben Coba Kohunlich Muyil San Gervasio Tulum Xcaret Xelha Yo'okop Reefs Arrecifes de Cozumel National Park Banco Chinchorro Other Akumal Mahahual Punta Allen Punta Sur Riviera Maya Sian Kaʼan Xcalak Yum Balam

• Sistema Sac Actun and Sistema Dos Ojos
• Caves of Mexico
• Landforms of Quintana Roo
• Limestone caves
• Sinkholes of Mexico
• Tulum (municipality)
• Natural history of Quintana Roo
• Paleoanthropological sites
• Underwater diving sites in Mexico
• First 100 IUGS Geological Heritage Sites