Cenote
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A cenote (pronounced in Mexican Spanish seh-no-teh and in English say-no-tay, plural: cenotes; from Yucatec Maya dzonot) is in the Yucatan Peninsula a type of freshwater-filled limestone sinkhole or doline. The name derives from a Maya word, dz'onot. The term is also nowadays increasingly used to describe similar karst features in other countries such as Cuba and Australia, in addition to the more generic term of sinkholes. As cenotes are filled with groundwater, water flows through them may be very slow, being on the order of 1 - 1000 m per year. In many cases the cenote is known to connect to an underlying cave system and the water flow rates through the cave may be 1-1000 m per day. Cenote water is often very transparent and fresh, as the water comes from rain water infiltrating slowly through the ground, and therefore there is very little suspended particulate matter. Cenotes around the world attract cave divers as many cenotes are entrances to the underlying flooded cave systems some of which have been explored to more than 100 km in length.
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[edit] Cenote Geology
Cenotes are formed by dissolution of a subsurface void which may or may not be linked to a flowing cave system, and subsequently upwards collapse of the rock into the void. The rock that falls into the water below will then be slowly removed by further dissolution providing space for more collapsing rocks. The rate of collapse will be increased at low sea-level stages as the rock above the void wil no longer be partially supported by the buyancy of water, and therefore is more likely to collapse at low sea level when the water levels are below the level of roof of the void. Cenotes may be fully collapsed creating an open water pool or partially collapsed with some portion of a rock roof overhanging the water below. The stereotypical mature cenotes often resemble small, circular ponds measuring some 10's of metres in diameter with sheer drops at the edges.
In coastal locations, and notably along the Caribbean and Gulf coast of the Yucatan Peninsula, the cave systems underlying some cenotes are known to flow out to the ocean and therefore the cenotes are the entry points into the underground rivers of this area.
Where collapse and caves are deep enough in a coastal aquifer, the interface between the meteoric fresh water and the underlying marine salt water coming in from the coast may be encountered. The contrast in density between fresh and saline water creates a visible blurry swirling effect where these waters are mixed. The interface between the fresh and saline waters is often called the halocline, meaning that there is a sharp change in salt concentration over a small depth change. It is also more simply referred to as the 'mixing zone'. The depth of the halocline is a function of climate, and how much meteoric water recharges the aquifer, and the distance from the coast. Further inland, the halocline is at greater depth, and in the Yucatan Peninsula this depth is 10-20 m below the water table at the coast, and 50-100 m below the water table in the middle of the peninsula, with saline water underlying the whole of the peninsula.
[edit] Cenotes and the Maya
Cenotes have long been the principal sources of water in much of the Yucatán peninsula, as there is an almost complete lack of any rivers throughout the region, and the lakes are scarce and often swampy in quality. Cenotes therefore are relatively easily accessible year-round water supplies of suitable quality. Major Maya settlements required access to adequate water supplies, and therefore cities including Chichén Itzá were built around these natural wells. Some cenotes like the Cenote of Sacrifice in Chichén Itzá played an important role in Maya rites. It was believed that these pools were gateways to the other world, and valuable items were sometimes thrown into them. Golden sacrificial artifacts were found in such cenotes, leading to the archaeological exploration of most cenotes in the first part of the 20th century. Edward Herbert Thompson, an American diplomat who had bought the Chichén Itzá 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 gods (Chaacs) by ritual casting into the cenote.
[edit] Cenote Park
Cenote Park, located at Playa del Carmen, Quintana Roo, Mexico, contains many cenotes. These cenotes provide access to extensive underwater cave systems such as the Nohoch Nah Chich cave. Caves such as Dos Ojos Cavern have attracted cave divers and there are organised efforts to explore and map the underwater systems.
[edit] Notable Cenotes
- Cenote of Sacrifice, Chichén Itzá
- Sacred Cenote, Chichén Itzá
- Zacatón
[edit] External links
