The Geology and Archaeology of Sinkholes

The Geology and Archaeology of Sinkholes A cenote (seh-NOH-tay) is the Maya term for a natural freshwater sinkhole, a geological feature found in the northern Yucatn Peninsula of Mexico, and other similar landscapes throughout the world. There are no rivers in the Yucatn; the regular high rainfall (1,300 mm or about 50 inches of rain falls every year) simply trickles through its calcareous landscape. Once below ground, the water forms a thin layer of water called a lens aquifer. Those aquifers flow horizontally, carving sinuous underground caves, and when the ceilings of those caves collapse, sinkhole openings to the surface are created. To be perfectly pedantic about it, the word cenote is a Spanish transliteration of the Maya word dzonoot or tsonot, which translates to water-filled cavity or natural well. Classifying Your Cenote Four general types of cenotes are defined in the geological literature: Open cenote or doline: a cylindrical shape with a large mouth and steep vertical walls (cenotes cilindricos in Spanish)Bottle-shaped or jug-shaped cenotes: a constricted mouth with a wider subsurface container (cenotes cntaro)Aguada-like cenotes: shallow water basins, typically degraded from a bottle or open cenotes (cenotes aguadas)Cavern cenotes: subterranean galleries with at least one cavity, access to which is a narrow opening that resembles a toads mouth (grutas) Uses of Cenotes As the only natural source of freshwater, cenotes are and were essential resources to people living in the Yucatn. Prehistorically, some cenotes were exclusively domestic, reserved for drinking water; others were exclusively sacred with their locations kept secret. A few, like the Great Cenote at Chichà ©n Itz, were sacred sites that served a number of religious purposes, including but not exclusively ritual sacrifice. To the ancient Maya, cenotes were passageways to the underground world of Xibalba. They were often also associated with the rain god Chaac, and sometimes said to be his dwelling place. Settlements grew up around many cenotes, and they were often part of or directly connected to the most important monumental architecture of the Maya capitals. Today cenotes are often fitted with an electric well, to allow people to easily draw water to the surface, which is then used for cultivation, agriculture or livestock. Field houses are built near them to support farming activities; shrines and masonry chapels are often found nearby. Some have developed complex water control features, tanks, and troughs. Alexander (2012) reports that cenotes are intimately tied to specific family groups, and often are the subject of ownership disputes over such issues as conservation and preservation. Yucatn Peninsula Cenotes Cenote formation in the Yucatn dates back several millions of years  when the Yucatn Peninsula was still below sea level. A prominent ring of cenotes results from the Chicxulub asteroid impact of 65 million years ago. The Chicxulub asteroid impact is often credited at least partly with killing off the dinosaurs. The impact crater is 180 kilometers (111 miles) in diameter and 30 meters (88 feet) deep, and along its outer limits is a ring of limestone karst deposits into which are eroded jug-shaped and vertical-walled cenotes. The Holbox-Xel-Ha fracture system in the northeastern coast of the Yucatn captures water from the east of the peninsula and feeding underground rivers and creating cavern and Aguada cenotes. Cenotes are still being created today: the most recent was July 2010, when a cave roof collapse in Campeche state created a 13 m (43 ft) wide, 40 m (131 ft) deep hole subsequently named el Hoyo de Chencoh. Non-Maya Cenotes Sinkholes are not exclusive to Mexico, of course, they are found throughout the world. Sinkholes are associated with legends on Malta (the legendary Maqluba collapse is thought to have occurred in the 14th century AD); and Lewis Carrolls Alice falling into Wonderland is thought to have been inspired by the sinkholes in Ripon, North Yorkshire. Sinkholes which are tourist attractions include North America:  Bottomless Lakes State Park and Bitter Lakes National Wildlife Refuge in New Mexico; Leon Sinks in Florida;  the submarine  Great Blue Hole  (Caribbean Sea);  Ik Kil  cenote in the Yucatan peninsula is a big draw to cliff divers.Europe: Lagunas de Canada del Hoyo (Spain), Modro Jezero (Red Lake) in Croatia;  and Il-Majjistral Nature and History Park in Malta.   Recent Cenote Research One is Rani Alexanders (2012) article about the changes in farming practices in the Yucatn during the historical period, including the changing roles of cenotes. Traci Ardrens paper on child sacrifice highlights the Maya mythology of the Great Cenote of Chichen Itza; Little Salt Spring (Clausen 1979) is a cenote in southwest Florida, where Paleoindian and Archaic use has been established. Charlotte de Hoogds MA on Chichen Itzas sacred well is worth a look. Some recent papers such as Munro and Zurita describe concerns about the worldwide protection and conservation efforts to counter increasing pressure from intensive tourist development, urban expansion and the non-indigenous use of the cenotes, particularly in the Yucatan, where pollution threatens to destroy the peninsulas only potable water source. Source: Alexander R. 2012. Prohibido Tocar Este Cenote: The Archaeological Basis for the Titles of Ebtun. International Journal of Historical Archaeology 16(1):1-24. doi: 10.1007/s10761-012-0167-0 Ardren T. 2011. Empowered Children in Classic Maya Sacrificial Rites. Childhood in the Past 4(1):133-145. doi: 10.1179/cip.2011.4.1.133 Chase AF, Lucero LJ, Scarborough VL, Chase DZ, Cobos R, Dunning NP, Fedick SL, Fialko V, Gunn JD, Hegmon M et al. 2014. 2 Tropical Landscapes and the Ancient Maya: Diversity in Time and Space. Archeological Papers of the American Anthropological Association 24(1):11-29. doi: 10.1111/apaa.12026 Clausen CJ, Cohen AD, Emiliani C, Holman JA, and Stipp JJ. 1979. Little Salt Spring, Florida: A unique underwater site. Science 203(4381):609-613. doi: 10.1126/science.203.4381.609 Cockrell B, Ruvalcaba Sil JL, and Ortiz Dà ­az E. 2014. For Whom the Bells Fall: Metals from the Cenote Sagrado, Chichà ©n Itz. Archaeometry:n/a-n/a. Coratza P, Galve J, Soldati M, and Tonelli C. 2012. Recognition and assessment of sinkholes as geosites: lessons from the Island of Gozo (Malta). Quaestiones Geographicae 31(1):25-35. de Hoogd C. 2013. Diving the Maya World: Reassessing old excavations with new techniques: a case study on the Sacred Cenote of Chichen Itza. Leiden: University of Leiden. Frontana-Uribe SC, and Solis-Weiss V. 2011. First records of polychaetous annelids from Cenote Aerolito (sinkhole and anchialine cave) in Cozumel Island, Mexico. Journal of Cave and Karst Studies 73(1):1-10. Lucero LJ, and Kinkella A. 2015. Pilgrimage to the Edge of the Watery Underworld: an Ancient Maya Water Temple at Cara Blanca, Belize. Cambridge Archaeological Journal 25(01):163-185. Munro PG, and Zurita MdLM. 2011. The Role of Cenotes in the Social History of Mexicos Yucatn Peninsula. Environment and History 17(4):583-612. doi: 10.3197/096734011x13150366551616 Wollwage L, Fedick S, Sedov S, and Solleiro-Rebolledo E. 2012. The Deposition and Chronology of Cenote T’isil: A Multiproxy Study of Human/Environment Interaction in the Northern Maya Lowlands of Southeast Mexico. Geoarchaeology 27(5):441-456.

How to Read and Write Files in Perl

How to Read and Write Files in Perl Perl is an ideal language for working with files. It has the basic capability of any shell script and advanced tools, such as regular expressions, that make it useful. In order to work with Perl files, you first need to learn how to read and write to them. Reading a file is done in Perl by opening a filehandle to a specific resource. Reading a File in Perl In order to work with the example in this article, youll need a file for the Perl script to read. Create a new text document called  data.txt  and place it in the same directory as the Perl program below. In the file itself, just type in a few names - one per line: When you run the script, the output should be the same as the file itself. The script is simply opening the specified file and looping through it line by line, printing each line as it goes. Next, create a filehandle called MYFILE, open it, and point it at the  data.txt file. Then use a simple while loop to automatically read each line of the data file one at a time. This places the value of each line in the temporary variable $_ for one loop. Inside the loop, use the chomp function to clear off the newlines from the end of each line and then print the value of $_ to show that it was read. Finally, close the filehandle to finish out the program. Writing to a File in Perl Take the same data file you worked with while learning to read a file in Perl. This time, you will write to it. To write to a file in Perl, you must open a filehandle and point it at the file youre writing. If youre using Unix, Linux or a Mac, you might also need to double-check your file permissions to see if your Perl script is allowed to write to the data file. If you run this program and then run the program from the previous section on reading a file in Perl, youll see that it added one more name to the list. In fact, every time you run the program, it adds another Bob to the end of the file. This is happening because the file was opened in  append  mode. To open a file in append mode, just prefix the filename with the  Ã‚  symbol. This tells the open function that you want to write to the file by tacking more onto the end of it. If  instead,  you want to overwrite the existing file with a new one, you use the  Ã‚  single greater than symbol to tell the open function that you want a fresh file each time. Try replacing the with a and you see that the data.txt file is cut down to a single name - Bob - each time you run the program. Next, use the print function to print the new name to the file. You print to a filehandle by following the print statement with the filehandle. Finally, close the filehandle to finish out the program.