Earth fissures are one of the geologic hazards of central and southern Arizona, and the first one recorded appeared near Eloy, in Pinal County, in 1929.
What they are
The Arizona Geological Survey describes earth fissures as open cracks in unconsolidated sediment on valley floors, caused by tension from land subsidence. They range from hairline cracks to 15 to 25 feet wide, run up to about two miles long, and can be up to 90 feet deep, with true depths possibly reaching the water table several hundred feet down.
Why they form here
Extensive groundwater pumping lowers the water table and compacts the sediment, and the land surface sinks. Near Eloy, subsidence measured 15.4 feet between 1952 and 1985. In a 2016 AP report, geologists said the valley around Eloy was 20 feet lower than 50 years earlier.
Where they are
Fissures occur in Cochise, La Paz, Maricopa, Pima and Pinal counties. Subsidence affects more than 3,000 square miles of Arizona. The Legislature charged the survey with mapping and monitoring fissures in 2006, and its Natural Hazards in Arizona Viewer shows current locations.
Why it matters for excavation
- The survey lists cracked roads, broken pipes and utility lines, cracked foundations and damaged well casings among the damage fissures cause.
- Fissures can carry runoff and contaminated water toward aquifers, and monsoon rain can quickly widen and deepen them.
- The survey advises keeping runoff out of fissures and consulting a geotechnician about their extent and damage.
Before you build or dig
- Look up the parcel on the survey's Natural Hazards in Arizona Viewer.
- If a fissure is nearby, bring in a geotechnical professional before designing drainage or foundations.
- Report a new fissure to the survey (azgs-info@email.arizona.edu) and your county emergency manager.
Sources
- Arizona Geological Survey: Earth Fissures & Subsidence
- ABC15 / Associated Press: Earth fissures linked to sinking valley in southern Arizona (February 13, 2016)
Reviewed October 20, 2026. Rules, prices and contacts change, so check the source before relying on it.
Questions and answers
What causes earth fissures in Arizona?
The Arizona Geological Survey links them to land subsidence from extensive groundwater pumping, which compacts sediments and creates tension cracks on valley floors.
How do I check if a property has earth fissures?
Use the Arizona Geological Survey's Natural Hazards in Arizona Viewer, which shows mapped fissure locations.
Get it quoted
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