Fissures

Fissures

Earth Fissures in Arizona

Earth fissures are tension cracks that open as a result of soil subsidence due to severe pumping of groundwater.  As the ground slowly settles, cracks form deep down and propagate towards the surface, hundreds of feet above. Individual earth fissures can range in length from hundreds of feet to several miles, and can be less than an inch wide to several feet wide. Heavy Arizona rainstorms can erode fissure walls very rapidly, causing them to widen and lengthen suddenly. This can be very dangerous as gullies can form between 5 feet to 15 feet wide and can go tens of feet deep.

Arizona Geological Survey – Earth Fissure Mapping

In 2006, the Arizona Legislature charged the Arizona Geological Survey (AZGS) with mapping fissures throughout the State. The Arizona Geological Survey’s efforts are concentrated in Cochise, Maricopa, Pima and Pinal Counties, where fissures are known to occur. In June 2007, the Arizona Geological Survey published a series of maps of known or reported earth fissures for the four counties. Arizona Geological Survey identified 23 priority study areas throughout the four counties in Arizona. After the mapping was completed in an area, the information was then given to the Arizona State Land Department, who makes the map data available to the public through their interactive mapping site.

Phoenix, Arizona

Phoenix, Arizona

Phoenix, Arizona

Arizona Earth Fissure Frequently Asked Questions

What do I do once I know there is an earth fissure on my property?

You need to consult with a qualified Geotechnical Engineering company to review your options. Make sure that the Geotechnical Engineering company has qualified, registered geologists and engineers who have experience working with earth fissures. There are ways of managing earth fissures that allow residents and earth fissures to coexist. Running water erodes and widens fissures rapidly. Do not add water to the area, and if possible divert runoff from the fissure. Call Tennyson Foundation Repair for a Geotechnical Engineering Company referral in Arizona.

Why are earth fissures in the news these days?

Arizona Geologists have been aware of earth fissure hazards since the early 1960s. Arizona’s population is rapidly increasing and people are moving into former agricultural lands and encroaching upon earth fissures. As a result, more and more people, and their properties, are at risk from the hazards associated with earth fissures.

Why is Arizona Geological Survey mapping earth fissures?

Because the best way to manage the known earth fissures is to avoid building near them. This requires detailed mapping to identify fissure locations. The maps can provide the public with a first line of defense against these known earth fissures.

Phoenix, Arizona

Phoenix, Arizona

Phoenix, Arizona

Do earth fissures change over time?

Earth fissures are very dynamic and they constantly change in response to movement in the subsurface (continuing earth subsidence) and also respond to activity at the surface (run off from heavy rains). Runoff can quickly widen and deepen existing earth fissures. Arizona Geologists have been aware of earth fissure hazards since the early 1960s. Arizona’s population is rapidly increasing and people are moving into former agricultural lands and encroaching upon earth fissures. As a result, more and more people, and their properties, are at risk from the hazards associated with earth fissures.

Should I build over an earth fissure?

No! It is not recommended to build on top of an unknown earth fissure. Before you even consider building within an area of a known earth fissure you should first consult with a qualified Geotechnical Engineering company to review your options. You should build as far from any known fissure as possible. Fissures are easily de-stabilized and frequently occur in closely spaced sets. And remember, earth fissures are very dynamic and are capable of sudden changes in length and in width.

What is the recommended set-back for earth fissures?

Set-back policy, if it exists at all, is established by county and municipal governments, and thus varies from one locale to the next. Tennyson Foundation Repair recommends that you first consult with a Geotechnical Engineering company as early as possible when considering building within a known area of a fissure. Call Tennyson Foundation Repair for a Geotechnical Engineering Company referral in Arizona.

Where can I learn more about where earth fissures exist?

Visit the AZGS Earth Fissure Center at www.azgs.az.gov/EFC for earth fissure planning maps and reports. And there you’ll also find a link to the Arizona State Land Dept. 1:12,000 scale earth fissure map series.

Hazards Associated with Earth Fissures

Earth fissures and the associated erosional gullies pose a hazard to people, property, livestock, and especially to the foundation of your home.

Some common and potential hazards include:

  • Cracked or collapsing roads
  • Severed or deformed railroad tracks
  • Broken water supply pipes
  • Broken sewer lines
  • Damaged well casing or wellhead
  • Broken canal liners
  • Disrupted drainage areas
  • Human injury
  • Cracked home foundation and separated walls
  • Livestock and pet injury or death
  • Contaminated groundwater aquifer
  • Broken or disrupted utility lines
  • If you suspect that you have a fissure on your property in Arizona,

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