Just how can you tell when a sinkhole is going to form? The United States Geological Survey (USGS) says it's all about the type of ground beneath the surface and the water levels around that ground.
Map of Tri-State susceptibility (Click to enlarge)
Around 20 percent of the country lies in areas susceptible to sinkholes, and the Tri-State falls in that range, according to the USGS.
Sinkholes are most common in what geologists call "karst terrain," or regions where the type of rock below the land surface can be naturally dissolved by groundwater.
When water from rainfall moves down through the soil, these types of rock begin to dissolve and spaces develop underground.
When the spaces underground get too big to support the land above the spaces, a sudden collapse of the surface occurs.
Aquifer systems, or underground pools of water, are another factor in sinkholes.
From the USGS: "The sediment above the aquifer system may be delicately balanced by ground-water fluid pressure, meaning that the water below ground is actually helping to keep the surface soil in place. Groundwater pumping for urban water supply and for irrigation can produce new sinkholes. If pumping results in a lowering of groundwater levels, then underground structures could fail and thus sinkholes can occur."
Different Types of Sinkholes
The USGS categorizes sinkholes into two types: Cover-collapse sinkholes and Cover-subsidence sinkholes.
Cover-collapse sinkholes develop rapidly, potentially over a period of hours, and can cause catastrophic damage.
Cover-subsidence sinkholes form slowly over time with the ground gradually deflating. These types of events can be less noticeable and go undetected for long periods until they reach a peak size.
Is There A Sinkhole On Your Property?
The USGS says there isn't a very efficient system to determine this quite yet, but they recommend property-owners/dwellers constantly observe for small holes in the ground or cracks in a structures foundation.
Property owners can also check to see if they live in areas over soluble types of rock. Reach out to local, county or state geological surveys to find this information, or go to USGS.gov for more guidance.