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The chasms usually take their time. It is a gradual process that involves groundwater slowly dissolving rock below the earth’s surface until it can no longer support the weight of the earth’s surface, which causes the earth’s surface to collapse and results in a depression or a hole in the ground.
Although sinkholes are relatively rare in the United States, when they do occur they can be catastrophic. Sinks are most common in Alabama, Florida, Kentucky, Missouri, Pennsylvania, Tennessee, and Texas.
If you want sinkhole insurance, you will need to purchase additional coverage.
Home insurance and sinkholes
A standard home insurance policy excludes “earth movements” including sinkholes. This means you won’t be covered if a sinkhole damages your home or property.
You can often find sinkhole coverage as an endorsement (sometimes called an endorsement) to a home insurance policy, depending on your insurance company.
Some states, such as Florida and Tennessee, require home insurance companies to offer sinkhole insurance as optional coverage. But some insurance companies include sinkhole insurance in their policies. For example, Erie insurance includes sinkhole coverage for Tennessee policyholders.
Here’s an overview of sinkhole insurance in states where sinkholes are most common:
- Alabama. Alabama homeowners may be able to purchase sinkhole coverage from their insurers for an additional fee.
- Florida. Florida home insurance companies are required to offer sinkhole coverage at an additional cost. Florida home insurance companies are required to cover “catastrophic collapse of plant cover.” (More on this below.)
- Kentucky. Kentucky homeowners may be able to purchase sinkhole collapse coverage as an optional type of coverage.
- Missouri. Missouri homeowners may be able to purchase sinkhole collapse coverage as an endorsement from their home insurance company. If you can’t get coverage from your insurer, you may be able to purchase a stand-alone sinkhole policy through the Missouri FAIR plan.
- Pennsylvania. Pennsylvania homeowners will need to apply for sinkhole coverage from their insurers for an additional cost.
- Tennessee. Every Tennessee home insurance company is required to provide sinkhole coverage to homeowners.
- Texas. Homeowners in Texas may be able to purchase sinkhole coverage as an endorsement to a home insurance policy.
Florida and “catastrophic land cover collapse”
Florida has more sinkholes than any other state, and home insurance companies are required to cover “catastrophic land cover collapse.” But it can be confusing because the catastrophic collapse of land cover is not the same as a sinkhole under Florida law.
Florida law defines a sinkhole as:
A landform created by subsidence of soil, sediment or rock, the underlying strata being dissolved by groundwater. A sinkhole can form by collapse in underground voids created by the dissolution of limestone or dolomite or by subsidence as these strata are dissolved.
Catastrophic collapse of vegetation cover is defined as “geological activity” which meets the following four criteria:
- The sudden collapse of the vegetation cover
- Ground cover depression clearly visible to the naked eye
- Structural damage to the building, including its foundation
- The structure is condemned and ordered to be evacuated by a government agency
This means that if your home is damaged by a sinkhole but does not meet the above four criteria, your insurance company is unlikely to cover the damage as part of a “catastrophic collapse in plant cover.” For example, the house might have cracks in the foundation but it is still habitable and not condemned by a government agency.
All home insurance companies in Florida are required to offer sinkhole insurance as an endorsement. Your home insurance company may require an inspection of your property before extending coverage. If there is already sinkhole activity or some distance from the house, the insurance company might refuse to offer sinkhole coverage.
If you live in Florida and your home insurance company denies coverage for a sinkhole claim or you disagree with the repair method, you can participate in the Florida Department’s Neutral Assessment Program. of Financial Services. This program assigns a geologist or professional engineer as a third party to assess the existence of sinkhole activity and the method of repair.
What causes a sinkhole?
Sinkholes are most common where the rock below the surface is karst terrain, which includes limestone, gypsum, and dolomite. About 20% of the land surface of the United States is karst.
As the rock dissolves, spaces and caverns develop underground. Sinks usually form very slowly and little change is noticed over time, but they can form suddenly when a collapse occurs.
There are three main types of chasms:
- Pits of dissolution. These occur in areas where there is little soil or vegetation on limestone or other rocky substrates. Rain and runoff water flow through crevices in the bedrock and dissolve it. Over time, a depression gradually forms.
- Cover-subsidence sinkholes. These occur in areas where sand covers the bedrock. Individual grains of sand move downward through the openings in the rock, gradually causing the soil surface to sag. Like Dissolution sinkholes, cover-sink sinkholes occur slowly.
- Cover the chasms. These occur in areas where the bedrock is covered with a significant amount of clay. These form similarly to cover-sag sinkholes, but the cohesive nature of clay allows a “bridge” to form over an expanding cavity. When the overlying roofing material can no longer support its own weight, the layer collapses. It can happen suddenly and be catastrophic.
Sinks can be triggered by natural events, such as heavy or prolonged rains or periods of drought. But sinkholes can also be triggered by human activities, such as:
- Adding weight above the cavities. This includes the development of housing, the construction of roads or structures and artificial ponds.
- Overpumping of existing water supply wells or the drilling of additional wells in the area. This lowers the water table and leaves cave roofs unsupported.
How to spot chasms
The chasms often develop gradually. If you live in an area prone to sinkholes, here are some signs to watch out for:
- Cracks develop around doors and windows
- Doors and windows that do not open and close properly
- Deep cracks in pavement, driveway and driveways
- Plumbing or electricity interrupted due to a sinkhole that damages utility lines
- A circular depression in or near your garden
- Fallen trees or fence posts
- Objects previously buried such as a foundation or fence posts that have become exposed when the ground sinks in
- Formation of small ponds as precipitation accumulates
- Openings in the ground where rainwater disappears
- Vegetation that withers and dies because water is dragged down a sinkhole
- Suddenly dropping water well levels
- Muddy or cloudy well water
What should I do if I have a sinkhole?
If you live in an area prone to sinkholes, it is a good idea to discuss with your home insurance agent the option of adding optional cover for sinkhole damage before it is too late. Damage caused by sinkholes is usually not covered by a standard home insurance policy, and you cannot add coverage after the damage has been done.
If you think you have a sinkhole on your property, here are some steps you can take:
- If you are concerned that the sinkhole could affect service lines, such as gas, sewer, and water, contact your utility companies.
- Contact your national geological survey for further advice
- Consider consulting a professional land surveyor, hydrologist, geologist, or geotechnical engineer to help mitigate the damage. Here is a list of professional organizations.