Geologists unconcerned about Del. sinkholes

When a Florida sinkhole swallowed up a house and a resident one night late last February, residents began seeing a wave of destruction caused by sinkholes around the state. Delaware residents, however, have no need to worry, according to Delaware geological scientist William Schenck.

In the past 34 years, two sinkholes have formed in the Hockessin Valley area of Delaware, Schenck said. His research has shown that Delaware is not likely to be affected by a major sinkhole.

According to the Delaware Debris Pit Program, sinkholes are large spaces underground that become exposed at the surface. They may appear small at the surface but can be cavernous immediately underneath ground.

Schenck said cavities and caverns can form from standing ground water moving through fractures in limestone or marble, causing it to dissolve.

Places in Delaware most susceptible to forming these caves are restricted to areas underlain by Cockeysville Marble or metamorphosed limestone, areas mainly located in Hockessin-Yorklyn Valley and the Pleasant Hill Valley, Schenck said.

Although Chris Myers, president of the university’s geology club, said he has noticed a national increase in the presence of these hazards, he has never seen a sinkhole in person. He said he does not think Delaware residents have to be worried about sinkholes in the future because of the state’s size.

“Sinkholes are becoming more noticeable as the U.S. becomes more populated,” Myers said. “Delaware is a small state though, so the chances of a sinkhole here are highly unlikely.”

Sinkholes are defined by any size large enough for the hollowed underground area to fall in, according to Schenck. The recent sinkhole in Florida was over 50 ft deep, and others can be up to hundreds of feet deep, Schenck said. He remains confident that Delaware will never see a sinkhole of this magnitude though.

“The ones in Delaware were only 10 to 15 ft. deep, so a hole developed,” Schenck said. “One of these was under Old Lancaster Pike and one was in a field near Swift Park.”

David Wunsch, a state geologist and director of the Delaware Geological Survey, studies the rocks and geological mapping of northern Delaware relevant to sinkhole development. Wunsch said he also believes Delaware residents will not encounter large scale sinkholes in the future.

“There are some areas of northern Delaware that are underlain by slightly soluble rock or marble that can develop sinkholes,” Wunsch said. “But, they typically don’t dissolve in the catastrophic fashion, like in areas such as Florida or Kentucky.”

The first indicator of a sinkhole’s development is when the ground begins to cave in and there is a visible depression or hole through the grass or ground. When that is visible, it’s already too late to stop the sinkhole, Schenck said. However, depending on the severity of the sinkhole, it can be possible to restore the ground.

“If it’s small, like Delaware’s were, then you excavate to find the bottom of the cavity and fill it in,” Schenk said. “But for some, like the one in Florida, you can only move away from because it’s too large to fill in.”

Although there aren’t any indicators for identifying sinkholes before they grow, people can make some efforts in terms of preventing disasters.  
In order to avoid sinkholes, homeowners and developers should learn more about the geology of the land where property is being built and the hazards associated with it, both in the present and in the future, Schenck said.

Certain counties in Delaware restrict landowners from developing over areas where there is Cockeysville Marble to prevent people from falling victim to the dangers of this geological hazard, Schenck said. He recommends that residents be aware of all possible surrounding geological hazards before deciding on a location to build.

Myers also said there is not a lot people can do in order to prevent or identify potential sinkholes. People should do their research and figure out where in the country they are most prevalent and avoid living in those areas, Myers said.

“If you’re uneasy about living near a volcano, you don’t live near a volcano,” Myers said. “Same goes for sinkholes. If they scare you, then avoid the places where you hear about them happening the most.”