A sign in Cochise County, Arizona, warning residents of possible Earth fissures.
A sign in Cochise County, Ariz., warning residents of possible Earth fissures. More than 300 kilometers of these cracks have appeared in at least four counties in central and southern Arizona. Credit: Joe Cook

Newly melded with the University of Arizona at a reduced level of funding, the Arizona Geological Survey (AZGS) might need to shut down a program more than a decade old under which it has mapped fissures in the Earth that plague the state, officials at the geology agency say. Currently, AZGS maps the locations of and monitors the huge cracks that can threaten lives and property when they suddenly form in Arizona’s cities and deserts.

Last month, in response to legislation signed in May by Arizona Governor Doug Ducey, AZGS moved its offices into smaller quarters at the university, which has agreed to provide the $941,000 the agency would have otherwise received from the state for fiscal year (FY) 2017.

In Arizona, FY 2017 began 1 July 2016. After the current fiscal year ends, AZGS becomes a “soft money” organization, said Michael Conway, chief of the Geological Extension Service at AZGS, which means the agency will have to secure funds through research grants.

If the survey can’t secure those funds, it along with the Earth fissure mapping program, “could potentially go away entirely after a year or two,” Conway said. Some Arizona state legislators have said they will try to restore funding to the agency.

When the Ground Splits

In Arizona, water and natural gas pumping erode from below; as the land slowly sinks, hairline fractures form at the surface. If a storm suddenly hits, the weight of the water can turn the subtle fracture into a chasm. Fissures sometimes extend more than a kilometer and can yawn several meters wide and tens of meters deep.

Rodgers fissure in Maricopa County. The fissure opened in 1997 following heavy rains from Hurricane Nora. Initially, the crack stretched 1200 meters long, 3 meters wide, and 10 meters deep in some places. Since 1997, the crack has grown in length another 400 meters. Credit: Joe Cook

Quickly developing areas, such as Maricopa and Pinal counties in the southern portion of the state, run an especially high risk of fissures, Conway said. When the land was mainly used for agriculture, farmers pumped out groundwater faster than they replenished it, leaving behind unstable ground. When fissures appeared, farmers tilling the fields filled them in, obscuring them from view. Dirt moved from construction projects have also filled the cracks.

Such hidden cracks can remain hazards, said Joe Cook, a research geologist at AZGS and manager of the Earth fissure mapping program. For example, at some time since the 1960s in Chandler Heights, an unincorporated community spanning both Maricopa and Pinal counties, developers filled in a previously known fissure. In 2005, a storm dumped about 5 centimeters (2 inches) of rain on the residential area in just an hour, reopening the fissure, which measured 12 meters (39 feet) deep in some places.

Arizona lawmakers subsequently passed legislation requiring the survey to map and monitor any existing fissures (the following year, the crack opened once again, swallowing a resident’s horse). Cook and other AZGS scientists have mapped nearly 300 kilometers of Earth fissures using GPS and said there may be another 300 kilometers of unconfirmed fissures based on old reports and satellite images.

“Occasionally, you can see [fissures] in Google Earth if the timing is just right,” Cook said. “But usually, the field is tilled annually, and any trace is erased.” The fissures might not affect a farmer now, but if the agricultural land is converted into residential developments in the future, “they could be a hazard to those homes,” he continued.

Threat to Houses

Once Cook visits and measures the fissures, he processes and uploads all his data to create maps, including an interactive map accessible to the public. The maps are of particular interest to realtors concerned with selling homes and city developers building roads or neighborhoods.

“When we were in the middle of the mapping program, we [were] receiving 75–100 requests per year” for information from realtors and developers who wanted to find out more about fissures, Conway said.

When a fissure opens near residential or private property, it can damage utility lines and walls and change the drainage of the surrounding landscape.

When a fissure opens near residential or private property, it can damage utility lines and walls and change the drainage of the surrounding landscape, which alters the flooding hazard, Cook said. That’s why realtors representing home buyers and developers looking to build often need detailed information about existing fissures.

The legislation requiring AZGS to map Earth fissures also requires home sellers to disclose whether there is a fissure on their property, but if the mapping program ends because of a choked funding stream, existing maps won’t be updated, Cook said. What’s more, if new fissures form, home sellers may not “have to disclose anything because there won’t be an additional map that shows anything,” he added.

Conway worried about “all the [fissure maps] we have posted online and made available to everyone.” When AZGS becomes a soft money organization, “I don’t know what happens to these things,” he said. “Who would step up and sustain that data? It certainly doesn’t look like it would be the state of Arizona.”

—JoAnna Wendel, Staff Writer


Wendel, J. (2016), Earth fissures may no longer get mapped in Arizona, Eos, 97, https://doi.org/10.1029/2016EO055943. Published on 18 July 2016.

Text © 2016. The authors. CC BY-NC-ND 3.0
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