Earth fissures are tension cracks in the soil that result from land subsidence, which is caused most commonly by ground water withdrawal, oil extraction, dissolution of soluble rocks and underground mining. One cannot predict with certainly where new fissure may develop.
In the earliest stages of development a fissure may appear as a series of small depressions or a tiny crack only a fraction of an inch wide and tens of feet wide. When more fully developed a typical earth fissure is 5 to 10 feet wide at the surface and 5 to 30 feet deep. A large fissure at the surface results from a large quantities of soil or sediment being washed down into a crack that may be only a few inches wide but up the several hundred feet deep and a mile or more in length.
Earth fissures can cause significant damage to structures such as buildings, roads, pipelines, and aqueducts. Houses have been completely destroyed by fissures that opened up beneath them. They can also provide a conduit for surface pollution to reach aquifers and pose a potential to safety to humans and animals.
Earth fissures are serious geologic hazards and their impacts will increase as Arizona’s population continues to grow.
For information about Soils Subject to Fissures in this report, contact the Arizona Geological Survey, (520) 770-3500 or http://azgs.az.gov/hazzards.htm
Source: Arizona Geological Survey
