They can be shallow enough that only a few grains of sand could fill them or deep enough to consume a car. In the geological world, they’re called earth fissures, and the Arizona Geological Survey is in the process of mapping their existence in Pinal, Cochise, Maricopa and Pima counties. According to the Arizona Geological Survey, earth fissures are associated with extensive ground water mining. In Arizona, fissures were first discovered near Eloy in 1929. Some of fissures in Arizona can be miles in length, up to 15 feet wide and 100s of feet deep. The Arizona Geological Survey has defined 23 study sites, with 12 of those areas being in Pinal County. “Pinal County has more earth fissure studies than any of the other counties we are looking at,” said Michael Conway, a spokesman for the Arizona Geological Survey. Recently Conway’s group, which the Arizona legislature charged with completing the study of the four counties in 2007, completed several of the sites in Pinal County and hopes to have a new online tool on their Web site in the coming months to help residents and others easily identify the location of fissures. The closest fissures to Maricopa lie a couple miles west of the city along Highway 238 in a study area called Heaton. In this area exists a mile-long unconfirmed fissure and several shorter, confirmed fissures. An unconfirmed fissure is one that has been reported to the organization and documented in the past, but cannot presently be seen because it has been plowed over by farmers. Fissures develop when the ground water consumption causes the land to collapse and crack. “The majority of these fissures occur in areas that at one time were agricultural, and a lot of water was pumped from the ground,” Conway said. “That is why we see so many of these fissures in Pinal County.” The maps are intended to be a tool to help developers, real estate agents and homebuyers make decisions about where to develop or buy. The maps could keep someone from making a costly or devastating mistake, Conway added. Some of the more notable problems associated with fissures have been the foundations of homes collapsing and even one instance of a cow falling into a large fissure. While no known fissures exist in the city of Maricopa, some other areas in Pinal County are not so lucky. Eloy, Arizona City and Picacho are in an area that has been tabbed as a fissure study zone. One recently documented fissure in this area is a 3.5-mile crevice in the Greene Wash area about six miles south of Arizona City; researchers also discovered 5.5 miles of unconfirmed fissures in the same area. Another problematic fissure has been identified in the Picacho area and runs across Interstate 10. “It is a fissure ADOT is going to have to address to prevent future road repairs,” Conway said. The Arizona Geological Survey has been known about many of the fissure areas since the 80s and 90s, but Conway said the group is discovering new fissures all the time. “We will often go out to study a fissure and find multiple others,” he said. When the geologists study fissure areas, they mark the location of the cracks on a map and record observations, such as the fissure's size, depth, steepness and the type of vegetation growing in or near it. The map also shows reported fissures that may be covered over at the surface. “The science of earth fissures is still developing, and geologists are learning more about it as the mapping project continues,” Conway said. "A lot of what we know comes from word of mouth." The group has a 2011 deadline for the completion of the fissure maps in the four-county area and would like to eventually map the entire state. For more information on the project or to view fissure maps, visit www.azgs.az.gov. To report a fissure, e-mail fissures@azgs.az.gov. Submitted photo |