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What Causes Sinkholes

Updated on March 14, 2015

How and Why Sinkholes Form

Entire buildings, lawns, houses and parts of highways and roads have abruptly sunk into the ground beneath them. On occasion there may be hints that the ground is opening, however more often than not, structures fall into the bedrock without any warning at all. Sinkholes that develop gradually are usually not noticed by anyone. The roof of an underground cavern, for example, eventually caves in causing everything on top to fall in.

Sinkholes Turned Into Swim Parks and Lakes

Sinkholes can be shallow or deep, and large or small. They generally appear suddenly and occur all over the world, however, they are more prevalent in some areas than in others. A sinkhole in Oman was turned into a swim park and the Kingsley Lake sinkhole in Florida now has several hundred docks with campgrounds and skiing. The size measures 2,000 feet in diameter with a depth of 90 feet at the deepest part. Florida has the most sinkholes in the U.S. compared to any other state and many of their lakes began as sinkholes.

The vegetation over a sinkhole is unable to receive sufficient nutrients resulting in poor growth. If one opens near a house it can destroy walls, joints and the foundation and if it's large enough, the whole house can sink. Large cracks may be observed on exterior blocks and around some of the joints.

There may be deep cracks and separations in sidewalks and driveways and window and door frames can warp causing them to gradually become more difficult to open and close. If you would like the ground and foundation of your premises investigated to determine the possibility of a sinkhole, your insurance company can assist you with who to contact in your area.

Primary Causes of Sinkholes

Rock that is constantly exposed to acidic water over time progresses into a process of erosion that eventually creates voids under the ground. Rainwater can be mildly acidic and becomes more acidic as it travels down over decomposing plant material. As the dissolving of rock remains constant, the sediments on the surface collapse into the underground cavity creating a sinkhole.

Droughts, as well as heavy rains, cause sinkholes. Sudden bursts of water can flood the cavity breaking up the ground around it. Droughts change the water table and cause a dragging effect leading to collapse of the surface sediments. A moderate level of water firms up the ground so it doesn't sweep away during construction of buildings, but when overly saturated with water, it may sink.

Dissolving Limestone and Dolomite Rock

Sinkholes in the U.S. most commonly occur in the states of Florida, Alabama, Kentucky, Pennsylvania, Texas, Missouri and Tennessee. The rock in these areas is mostly limestone or dolomite carbonates which dissolve and evaporate easier compared to other forms of rock. If you reside either in any of these states, or in any area where the risk for sinkholes is high, ensure that your insurance coverage includes damages that may occur.

A Guideline If You Notice a Sinkhole

  • Contact emergency management of your county for assistance.
  • Keep children and pets away.
  • Surround the area with rope, fence or tape.
  • Record a video and/or take pictures from different angles.
  • Don't use it for any waste or chemicals as it would seep into drinking water.
  • Watch to see if it expands, sinkholes follow the path of least resistance.
  • Call your insurance company and consult your policy if there is structural damage.

Who is Liable For Damages or Injuries Caused by a Sinkhole?

The owner of the property is usually held liable if someone were to get injured. If your car ever ends up in a sinkhole, whether by driving along the road or while parked, most if not all auto insurance companies file the incident under 'acts of god' and therefore do not generally cover damages.

Other Causes of Sinkholes

Water drainage from underground pipes and sewage systems that were in need of maintenance, and septic tanks that have broken. The upper layer begins to swell with water while the rock corrodes and eventually breaks apart and falls into the cavity taking whatever is on the surface down with it. Main water lines breaking or bursting is a very common cause of small and large sinkholes in cities.

The surface level of a void, a hole under the ground, can reach a point of collapsing whereas it falls into the space. This form of sinking is referred to more specifically by geologists as subsidence; when the motion of the Earth's surface shifts downward creating a sinkhole.

Excavation dig sites have a proper method to re-compact the soil after excavation work has been completed. A sinkhole can occur by improper compacting of the soil.

Whether in a car, a building or on foot, hopefully you have never experienced the ground caving in. Although the odds are very slim, if by any chance the ground were to suddenly open, you will now be familiar enough with sinkholes to know what happened and what to do.

Liz Olivia


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