| Sistema Sac Actun | |
|---|---|
  Sistema Sac Actun Location in Mexico | |
| Location | Tulum Municipality,Quintana Roo,Mexico |
| Coordinates | 20°14′47.6″N87°27′50.8″W / 20.246556°N 87.464111°W /20.246556; -87.464111 |
| Depth | 119.2 meters (391 ft)[1] |
| Length | Underwater: 378.56 km (235.23 mi)[1] Total: 386.122 km (239.925 mi)[2] |
| Discovery | November 26, 1987 |
| Geology | Limestone |
| Entrances | 228Cenotes[1] |
| 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 theYucatán Peninsula with passages to the north and west of the city ofTulum. Discovery of a connection toSistema Dos Ojos in 2018 made it the longest known underwater cave system. As of January 2023[update], it is the second longest underwater cave system in the world, only surpassed bySistema Ox Bel Ha.
The remains of amastodon and a human female that might be the oldest evidence ofhuman habitation in the Americas have been found in the cave.
Exploration started fromGranCenote 5 kilometers (3.1 mi) west of Tulum. The whole of the explored cave system lies within theMunicipality of Tulum, in the state ofQuintana Roo.
In early 2007, the underwater caveSistema Nohoch Nah Chich was connected into and subsumed into Sac Actun making it thelongest surveyed underwater cave system in the world.[3] Sac Actun measured 230.8 km (143.4 mi) (after connecting withSistema Aktun Hu (34 km (21 mi)(in January 2011) and is, as of January 2023[update] with an explored length of 259.5 kilometers (161.2 mi), only surpassed by theSistema Ox Bel Ha at 435.8 kilometers (270.8 mi).[4][1] Since early 2007, these two caves have frequently exchanged the title of world's longest underwater cave.[5] Including connected dry caves makes Sistema Sac Actun 386.122 km (239.925 mi) long, the second longest cave in Mexico[2] and third longest worldwide.[6]
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 exhausted their oxygen supply.[7]
In 2018, the discovery of a link between the Sac Actun system (reported to be 263 km (163 mi) long) and theDos Ojos system in Tulum, Quintana Roo (84 km (52 mi) long) was reported.[8] The connection was found by the Gran Maya Aquifer Project (GAM), led by the cave diver and explorer Robbie Schmittner.[9] The combined system is reported to be the world's second longest underwater cave system known.
In March 2008, three members of theProyecto Espeleológico de Tulum andGlobal Underwater Explorers dive team, Alex Alvarez, Franco Attolini, and Alberto Nava, explored a section ofSistema Aktun Hu known as theHoyo Negro pit.[10][11] At a depth of 60 meters (200 ft) the divers located the remains of amastodon, as well as ahuman skull at 43 meters (141 ft) that might be the oldest evidence of human habitation in the Americas.[11] Additional bones were located and the skeleton was later identified as that of a teenage female now referred to asNaia.[12]
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