Sinkholes are notoriously hard to detect and difficult to prevent — but two Nova Scotia geologists say there are ways for people to protect their properties. 

A home in Falmouth, N.S., sunk into a sinkhole Labour Day weekend and is so badly damaged it has to be torn down. 

Deanne van Rooyen, a geology professor at Cape Breton University, said sudden depressions or holes in the soil, or extra cracks forming in a building's foundation could indicate a sinkhole is starting to form.  

"I would move my stuff," she said. "I don't think there's much you can do about preventing one once it's started, because once it starts showing any signs of happening, then that process is already well underway."     

The birth of a sinkhole

In Nova Scotia most sinkholes form when rocks like gypsum or limestone are slowly dissolved by water flowing through the soil, said van Rooyen. Over time a spring, an underground river or rainwater can wash away the rocks.

The acid in the water eats away at the water-soluble rock and over hundreds of years creates a small underground cave. Eventually, the cave can no longer support the weight of the earth above it and collapses, forming a sinkhole.  


A sinkhole on Cornwallis Street in Halifax in 2013 was caused by a broken water pipe. (CBC)

Much of the province, however, sits on rock that is not susceptible to sinkholes, so they rarely endanger people's homes. However, some parts of the province are vulnerable.

"In areas where there is limestone and gypsum it's fairly common," said Peir Pufahl, a professor of sedimentary geology at Acadia University.

He said many of the lakes in the Windsor area, where the Labour Day hole opened up, and in other parts of the Annapolis Valley were once sinkholes that filled in with water.

Planning is the best protection 

Oklahoma mine damage

Sinkholes usually form as a result of water eroding subterranean supports, but years of lead and zinc mining were responsible for this pit in Picher, Okla. (Charlie Riedel/AP)

Van Rooyen and Pufahl said before anyone builds a home they should check their property for any existing sinkholes, caves, or proximity to waterways. All of those things can make a home more vulnerable.

People can also consult maps from the province's Department of Natural Resources that outline an area's geological composition. Pufahl said they can also hire a geologist to examine their property if they want to be extra cautious.