A cenote (English: // or // ; American Spanish: [seˈnote] ) is a natural pit, or sinkhole, resulting from the collapse of limestone bedrock that exposes groundwater underneath. Especially associated with the Yucatán Peninsula of Mexico, cenotes were sometimes used by the ancient Maya for sacrificial offerings.
The term derives from a word used by the low-land Yucatec Maya—ts'onot—to refer to any location with accessible groundwater.Cenotes are common geological forms in low altitude regions, particularly on islands, coastlines, and platforms with young post-Paleozoic limestones that have little soil development.
Cenotes are surface connections to subterranean water bodies. [ better source needed ]While the best-known cenotes are large open water pools measuring tens of meters in diameter, such as those at Chichen Itza in Mexico, the greatest number of cenotes are smaller sheltered sites and do not necessarily have any surface exposed water. There are over 6,000 different cenotes in the Yucatán Peninsula in Mexico alone.
The term cenote has also been used to describe similar karst features in other countries such as Cuba and Australia, in addition to the more generic term of sinkholes.
Cenote water is often very clear, as the water comes from rain water filtering slowly through the ground, and therefore contains very little suspended particulate matter. The groundwater flow rate within a cenote may be very slow. In many cases, cenotes are areas where sections of cave roof have collapsed revealing an underlying cave system, and the water flow rates may be much faster: up to 10 kilometers (6 mi) per day.
Cenotes around the world attract cavern and cave divers who have documented extensive flooded cave systems through them, some of which have been explored for lengths of 340 km (210 mi) or more.
Cenotes are formed by dissolution of rock and the resulting subsurface void, which may or may not be linked to an active cave system, and the subsequent structural collapse. Rock that falls into the water below is slowly removed by further dissolution, creating space for more collapse blocks. The rate of collapse increases during periods when the water table is below the ceiling of the void, since the rock ceiling is no longer buoyantly supported by the water in the void.
Cenotes may be fully collapsed creating an open water pool, or partially collapsed with some portion of a rock overhanging above the water. The stereotypical cenotes often resemble small circular ponds, measuring some tens of meters in diameter with sheer drops at the edges. Most cenotes, however, require some degree of stooping or crawling to access the water.
In the north and northwest of the Yucatán Peninsula in Mexico, the cenotes generally overlie vertically extensive voids penetrating 50 to 100 m (160 to 330 ft) below the modern water table. However, very few of these cenotes appear to be connected with horizontally extensive underground river systems, with water flow through them being more likely dominated by aquifer matrix and fracture flows. In contrast, the cenotes along the Caribbean coast of the Yucatán Peninsula (within the state of Quintana Roo) often provide access to extensive underwater cave systems, such as Sistema Ox Bel Ha, Sistema Sac Actun/Sistema Nohoch Nah Chich and Sistema Dos Ojos.
The Yucatán Peninsula contains a vast coastal aquifer system, which is typically density-stratified.The infiltrating meteoric water (i.e., rainwater) floats on top of higher-density saline water intruding from the coastal margins. The whole aquifer is therefore an anchialine system (one that is land-locked but connected to an ocean). Where a cenote, or the flooded cave to which it is an opening, provides deep enough access into the aquifer, the interface between the fresh and saline water may be reached. The density interface between the fresh and saline waters is a halocline, which means a sharp change in salt concentration over a small change in depth. Mixing of the fresh and saline water results in a blurry swirling effect caused by refraction between the different densities of fresh and saline waters.
The depth of the halocline is a function of several factors: climate and specifically how much meteoric water recharges the aquifer, hydraulic conductivity of the host rock, distribution and connectivity of existing cave systems and how effective these are at draining water to the coast, and the distance from the coast. In general, the halocline is deeper further from the coast, and in the Yucatán Peninsula this depth is 10 to 20 m (33 to 66 ft) below the water table at the coast, and 50 to 100 m (160 to 330 ft) below the water table in the middle of the peninsula, with saline water underlying the whole of the peninsula.
In 1936, a simple morphometry-based classification system for cenotes was presented.
The classification scheme was based on morphometric observations above the water table, and therefore incompletely reflects the processes by which the cenotes formed and the inherent hydrogeochemical relationship with the underlying flooded cave networks, which were only discovered in the 1980s and later with the initiation of cave diving exploration.
Flora and fauna are generally scarcer than in the open ocean; however, marine animals do thrive in caves. In caverns, one can spot mojarras, mollis, guppies, cat-fish, small eels and frogs. In the most secluded and darker cenotes, the fauna has evolved special features to live in an environment deprived of natural light. For example, many animals don't have pigmentation and they are often blind, so they are equipped with long feelers so that they can find food and make their way around in the dark.
Although cenotes are found widely throughout much of the Yucatán Peninsula, a higher-density circular alignment of cenotes overlies the measured rim of the Chicxulub crater. This crater structure, identified from the alignment of cenotes,but also subsequently mapped using geophysical methods (including gravity mapping) and also drilled into with core recovery, has been dated to the boundary between the Cretaceous (K) and Paleogene (Pg) periods, 66 million years ago. This meteorite impact at the Cretaceous–Paleogene boundary is therefore associated with the mass extinction of the dinosaurs and is also known as the Cretaceous–Paleogene extinction event.
In 2001–2002 expeditions led by Arturo H. González and Carmen Rojas Sandoval in the Yucatán discovered three human skeletons; one of them, Eve of Naharon, was carbon-dated to be 13,600 years old. 57 m (187 ft) the divers located the remains of a mastodon and a human skull (at 43 m [141 ft]) that might be the oldest evidence of human habitation in the region.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 (part of Sistema Sac Actun) known as the pit Hoyo Negro. At a depth of
The Yucatán Peninsula has almost no rivers and only a few lakes, and those are often marshy.The widely distributed cenotes are the only perennial source of potable water and have long been the principal sources of water in much of the region. Major Maya settlements required access to adequate water supplies, and therefore cities, including the famous Chichen Itza, were built around these natural wells. Some cenotes like the Sacred Cenote in Chichen Itza played an important role in Maya rites. Believing that these pools were gateways to the afterlife, the Maya sometimes threw valuable items into them.
The discovery of golden sacrificial artifacts in some cenotes led to the archaeological exploration of most cenotes in the first part of the 20th century. Edward Herbert Thompson (1857–1935), an American diplomat who had bought the Chichen Itza site, began dredging the Sacred Cenote there in 1904. He discovered human skeletons and sacrificial objects confirming a local legend, the Cult of the Cenote, involving human sacrifice to the rain god Chaac by ritual casting of victims and objects into the cenote.The remains of this cultural heritage are protected by the UNESCO Convention on the Protection of the Underwater Cultural Heritage.
Cenotes have attracted cavern and cave divers, and there are organized efforts to explore and map these underwater systems. They are public or private and sometimes considered as "National Natural Parks". Great care should be taken to avoid spoiling this fragile ecosystem when diving. In Mexico, the Quintana Roo Speleological Survey maintains a list of the longest and deepest water-filled and dry caves within the state boundaries. When cavern diving, one must be able to see natural light the entire time that one is exploring the cavern (e.g. Kukulkan cenote near Tulum, Mexico). During a cave dive, one passes the point where daylight can penetrate and one follows a safety guideline to exit the cave. Things change quite dramatically once moving from a cavern dive into a cave dive. Too many divers, even experienced ones, have died for ignoring safety recommendations.
Contrary to cenote cavern diving, cenote cave diving requires special equipment and training (certification for cave diving). However, both cavern and cave diving require detailed briefings, diving experience and weight adjustment to freshwater buoyancy. The cenotes are usually filled with rather cool fresh water. Cenote divers must be wary of possible halocline, this produces a blurred vision until they reach a more homogeneous area.
A sinkhole, also known as a cenote, sink, sink-hole, swallet, swallow hole, or doline, is a depression or hole in the ground caused by some form of collapse of the surface layer. Most are caused by karst processes – the chemical dissolution of carbonate rocks or suffosion processes. Sinkholes vary in size from 1 to 600 m both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide.
Cave diving is underwater diving in water-filled caves. It may be done as an extreme sport, a way of exploring flooded caves for scientific investigation, or for the search for and recovery of divers lost while diving for one of these reasons. The equipment used varies depending on the circumstances, and ranges from breath hold to surface supplied, but almost all cave diving is done using scuba equipment, often in specialised configurations with redundancies such as sidemount or backmounted twinset. Recreational cave diving is generally considered to be a type of technical diving due to the lack of a free surface during large parts of the dive, and often involves planned decompression stops.
Tulum is the site of a pre-Columbian Mayan walled city which served as a major port for Coba, in the Mexican state of Quintana Roo. The ruins are situated on 12-meter (39 ft) tall cliffs along the east coast of the Yucatán Peninsula on the Caribbean Sea in the state of Quintana Roo, Mexico. Tulum was one of the last cities built and inhabited by the Maya; it was at its height between the 13th and 15th centuries and managed to survive about 70 years after the Spanish began occupying Mexico. Old World diseases brought by the Spanish settlers appear to have resulted in very high fatalities, disrupting the society and eventually causing the city to be abandoned. One of the best-preserved coastal Maya sites, Tulum is today a popular site for tourists.
The Riviera Maya is a tourism and resort district south of Cancun, Mexico. It straddles the coastal Federal Highway 307, along the Caribbean coastline of the state of Quintana Roo, located in the eastern portion of the Yucatán Peninsula. Historically, this district started at the city of Playa del Carmen and ended at the village of Tulum, although the towns of Puerto Morelos, situated to the north of Playa del Carmen, as well as the town of Felipe Carrillo Puerto, situated 40 kilometres (25 mi) to the south of Tulum, are both currently being promoted as part of the Riviera Maya tourist corridor.
The Yucatán Peninsula, in southeastern Mexico, separates the Caribbean Sea from the Gulf of Mexico, with the northern coastline on the Yucatán Channel. The peninsula lies east of the Isthmus of Tehuantepec, a northeastern geographic partition separating the region of Central America from the rest of North America. It is approximately 181,000 km2 (70,000 sq mi) in area, and is almost entirely composed of limestone.
Dzibilchaltún is a Maya archaeological site in the Mexican state of Yucatán, approximately 10 miles (16 km) north of state capital Mérida.
Dos Ojos is part of a flooded cave system located north of Tulum, on the Caribbean coast of the Yucatán Peninsula, in the state of Quintana Roo, Mexico. The exploration of Dos Ojos began in 1987 and still continues. The surveyed extent of the cave system is 82 kilometers (51 mi) and there are 28 known sinkhole entrances, which are locally called cenotes. In January 2018, a connection was found between Sistema Dos Ojos and Sistema Sac Actun. The smaller Dos Ojos became a part of Sac Actun, making the Sistema Sac Actun the longest known underwater cave system in the world.
Sistema Nohoch Nah Chich, is located 16.5 kilometers (10.3 mi) south of Akumal in Tulum Municipality of Quintana Roo state, southeastern Mexico. It is part of the Sistema Sac Actun underwater cave systems.
Sistema Ox Bel Ha is a cave system in Quintana Roo, Mexico. It is the longest explored underwater cave in the world and ranks fourth including dry caves. As of May 2017 the surveyed length is 270.2 kilometers (167.9 mi) of underwater passages. There are more than 140 cenotes in the system.
The Deep Phreatic Thermal Explorer (DEPTHX) is an autonomous underwater vehicle designed and built by Stone Aerospace, an aerospace engineering firm based in Austin, Texas. It was designed to autonomously explore and map underwater sinkholes in northern Mexico, as well as collect water and wall core samples. The DEPTHX vehicle was the first of three vehicles to be built by Stone Aerospace which were funded by NASA with the goal of developing technology that can explore the oceans of Jupiter's moon Europa to look for extraterrestrial life.
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 339 metres (1,112 ft): the 392 metres (1,286 ft) plus deep Pozzo del Merro is deeper, but
The Sacred Cenote refers to a noted cenote at the pre-Columbian Maya archaeological site of Chichen Itza, in the northern Yucatán Peninsula. It is located to the north of Chichen Itza's civic precinct, to which it is connected by a 300-metre (980 ft) sacbe, or raised and paved pathway.
Sistema Sac Actun is an underwater cave system situated along the Caribbean coast of the Yucatán Peninsula with passages to the north and west of the village of Tulum. Discovery of a connection to the Sistema Dos Ojos in 2008 made it the longest known underwater cave system.
The Quintana Roo Speleological Survey (QRSS) was established in 1990 for the safe exploration, survey and cartography of the underwater and dry caves and cenotes of Quintana Roo, Mexico, supported by the National Speleological Society.
Chichen Itza was a large pre-Columbian city built by the Maya people of the Terminal Classic period. The archaeological site is located in Tinúm Municipality, Yucatán State, Mexico.
Ik Kil is a cenote outside Pisté in the Tinúm Municipality, Yucatán, Mexico. It is located in the northern center of the Yucatán Peninsula and is part of the Ik Kil Archeological Park near Chichen Itza. It is open to the public for swimming from 9am to 5pm all year long.
Chan Hol, part of the Toh ha cave system, is a cenote and submerged cave system in Quintana Roo, Mexico, of interest to paleoanthropologists. The remains of three prehistoric human fossils were discovered within the cave system. Along with Eve of Naharon, Naia, the Man of El Templo and the Woman of Las Palmas, the three fossils at Chan Hol are among several ancient Paleoamerican skeletons found in the submerged cave systems of the Yucatán Peninsula around Tulum, Quintana Roo.
Hells Bells are hollow bell- or cone-shaped structures of carbonate that can reach lengths of 2 metres. They are found underwater in El Zapote cenote in Quintana Roo, Mexico, on the Yucatan Peninsula; similar formations exist in other caves. In a certain depth range, such structures cover the entire surface of the cave including submerged tree trunks and other Hells Bells, although they never touch each other.