Media reports of sinkholes swallowing up buildings and cars have caught the attention of people around the country. Many may wonder what causes this natural phenomenon and whether they are at risk for having these sinkholes develop in their area of the country. Some factual information on sinkholes can help to allay fears and clarify the information.
What Are Sinkholes?
Sinkholes are depressions that occur underground that eventually open up on the ground’s surface. Sinkholes may be part of natural underground structures such as limestone that gradually erodes away. They may also be underground caves that suddenly collapse. They can occur when the water table beneath the ground lowers, creating greater pressure on carbonates and sandstone. The collapse of these underground hollows can be sudden and dramatic.
Types of Sinkholes
Two types of sinkholes are common. The covered-subsidence sinkhole is found in areas like the Shenandoah Valley where the ground is sandy. The soil collects over the hollowed area and gradually subsides over time. It is rarely a catastrophic event. Another type of sinkhole is the covered-collapse type. It generally occurs in clay-type soils. The soil gradually leaches into the hollow below it and creates a void that moves upward toward the surface. When the surface soil cannot support weight anymore, it collapses. This type makes the evening news shows because it is sudden and destructive. Sinkholes cost hundreds of thousands and even millions in damage to communities in vulnerable areas.
Sinkhole Facts
Sinkholes tend to be localized. When a sinkhole occurs, it tends to be limited in its extent. Few lives have been lost because of sinkholes, but such losses do happen. The person just happens to be standing where the sinkhole occurs. In a case in Florida, a man was in his bedroom when a large sinkhole collapsed. His body was not recovered. Generally, people are not recovered in sinkholes when they fall into an aquifer or sewage drain as a result of the break in the earth’s structure. A number of huge sinkholes have occurred around the world. One such sinkhole was in Winter Park, Florida in 1981. It swallowed an entire city block. In 2010, a sinkhole developed in Guatemala City, Guatemala that was 300 feet deep and 60 feet wide. In 2013, a sinkhole opened up beneath a resort hotel in central Florida near Disney World, collapsing a 3-story section and opening a 50-foot wide, 15-foot deep gap in the ground. The 35 guests escaped unharmed.
Where Do Sinkholes Usually Occur?
Florida is particularly susceptible to sinkholes because of the limestone that runs under the soil. Pennsylvania, New York, Indiana, Tennessee to Alabama, Minnesota, up through North and South Dakota and down to New Mexico all have limestone structures beneath the soil that can collapse. Around the world, Mexico, Italy, Yugoslavia, China and Russia all have areas of ‘karst’ structure which is susceptible to collapse (karst is landscape that is formed from the dissolution of soluble rocks such as limestone, dolomite and gypsum – learn more HERE.
Warning Signs of Impending Sinkhole
An impending sinkhole may give no warning sign at all. At other times, fresh cracks in the foundations of buildings may be evident. A doorframe may be suddenly askew and won’t shut properly. Unusual cracks in the ground that weren’t there before may be a sign of impending sinking. A tree may start leaning in a way it hadn’t before. These are some subtle indications that a sinkhole might be imminent.
What To Do If You Have A Sinkhole On Your Property
If you find a sinkhole on your property or have a sudden sinkhole event, get people and pets out of the area and rope it off to prevent injuries. Contact your insurance company for appraisal of the damage. If the sinkhole is large, call your local emergency management agency to assess the sinkhole to prevent further damage to people and property. Depending on the type of collapse, sinkholes may or may not be covered by your homeowners insurance. You may need an attorney to protect your interests in an insurance dispute.
