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 News Around the Republic of Mexico | August 2005 
Fissures in Jalisco a Cause for Concern
 Ulises Zamarroni - El Universal
| | Though the giant cracks in the earth that are endemic to the state have yet to cause serious human injury, experts say the potential for problems exists. |
Zacoalco de Torres, Jalisco - When a crack in the earth measuring 250 meters long, 75centimeters wide and 2 meters deep opened up earlier this month just outside of San Marcos Evangelista, Jalisco state, it was nothing new for local resident Refugio González Díaz.
"About a year ago, another crack appeared that was even bigger than this one," recalls the 70-yearold González Díaz. "That one swallowed up a cow."
For residents of this community in the municipality of Zacoalco de Torres, 40 kilometers southwest of Guadalajara, the appearance of large fissures in the ground is a common occurrence.
"My father would talk about how the earth used to open up about once every year," says González Díaz, "and just three years ago, a small crack opened up along one side of the town hall. And of course, then there was the one from last year: the one that got the cow."
González Díaz says that locals have learned to deal with the cracks and avoid injury or loss of property from them.
"You know that nothing will happen if you watch your step and be careful of where your livestock grazes," he says. "But it's not dangerous: it's just the way the earth here is and always has been."
According to experts, there are nine areas in the state of Jalisco that are prone to large fissures in the earth. And while the fissures have yet to cause significant damage or injury, authorities worry that nonchalant attitudes by residents of at-risk areas could result in future crises.
The head of Jalisco's Civil Protection Agency, Germán Pinto Aceves, says the fissure at San Marcos Evangelista appeared as a result of recent heavy rains. And the open cracks that are endemic to that area, he explains, are formed via an erosion process resulting from underground water flow.
"This is what we might call 'tube-ification,' where large amounts of water erode the subsoil," he says. "Then, when the soil above the drainage 'tubes' begins to dry, it collapses and we see the cracks."
Pinto Aceves says that the large fissure that opened recently is part of a larger complex of cracks covering an area of six hectares. There are three principal fissures in the complex, he says, and these are connected by a series of smaller cracks.
And while the fissure complex, less than a kilometer from the center of San Marcos Evangelista, lies in a non-residential zone, it is still an area frequented by local farmers and ranchers. So to protect against possible injuries to people or livestock, officials have cordoned off the area.
Local parents are also doing their part to prevent accidents. José Pablo Pérez Dávila, 9, says that his parents have forbidden him and his siblings from playing in the area where the cracks have formed.
"They asked us not to go near (the area)," he says. And recalling the accident last year involving the cow, José Pablo notes: "And that's why we can't let the dogs go over there, either."
A REGIONAL PROBLEM
According to researcher Luis Valdivia Ornelas at the Geographic Institute of the University of Guadalajara, fissure fields such as the one at San Marcos Evangelista have been appearing throughout the westerncentral areas of the country during at least the past 20 years. The problem can be caused, he says, by either the accumulation of excess water in the subsoil, or by the over-extraction of water from the underlying aquifer.
"Unfortunately, the cracks are getting more and more common," he says. "And there are many cases throughout the Bajio (west-central Mexico) region. There are serious problems due to water over-extraction in Silao and Celaya (Guanajuato state), as well as in Aguascalientes. The problem is also present in other claysoiled areas like Ixtapaluca in eastern Mexico City."
But of all the affected areas, Valdivia Ornelas says that Jalisco is the state where the phenomenon is most common.
"Jalisco is especially susceptible because it has a high population density and a lot of economic activity," he says. "That means that a lot of water is needed, and therefore, there is a lot of extraction from the aquifer."
Within Jalisco, the municipalities of Zapopan, Chapala, Zacoalco de Torres, Ameca, Sayula, Ciudad Guzmán, Autlán and El Grullo all have active crack systems.
"We are talking about basin areas with clay-like soils that behave in an unusual manner in the presence or in the absence of water," says Valdivia Ornelas.
WORRIES ARISE
One of the state's most notable fissures lies in the town of Chapala, where three years ago, an 800meter-long crack forced the displacement of the town hall. In addition, 20 local homes were evacuated due to the geological phenomenon.
"There was an evacuation at the time," says Valdivia Ornelas, "but later on, when the levels of (Lake Chapala) returned to normal, the subsoil stabilized and the risk lessened."
But according to the researcher, of all the affected areas, the municipality of Ameca, 90 kilometers east of Guadalajara is the most at-risk area.
"We did a study in Ameca two years ago and found that around a thousand homes in the town are in areas of potential danger."
Despite the fact that the fissures are often caused by over-extraction of water, Valdivia Ornelas says that the risk of a new crack opening is highest during the wettest months of the year.
"It's because of the softening of the soil" during the rainy season, he says.
"The risk is not high, but it does exist," he says. "Above all, because there are existing fissures that fill in and then people forget that they are areas of potential danger." He says that this past July 8, a crack reopened in Santa Lucía in the municipality of Zapopan that had not been seen since 1987. In Nextipac, also in Zapopan, a kilometer-long crack measuring 80 meters wide caused the evacuation of 75 families when it opened up just over a year ago. Now, with the fissure filled in, 30 families have moved back into the area.
Furthermore, in Ameca, hundreds of homes of various sizes have been built in the town's center directly above filled-in fissures. And in Chapala, local authorities admit, numerous homes and business sit precariously close to the town's active fissure system.
Germán Pinto Aceves says that Jalisco's Civil Protection Agency is concerned by the number of people living on or around potential fissures.
"There is still a degree of risk because people have filled in the cracks with rubble, and this material blocks the flow of water within the soil," he says. "What we believe, and what we're afraid of, is that this creates new channels or else widens the existing channels."
And because these underground channels are difficult to detect, says Pinto Aceves, new fissures could open up at any time. |
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