CHARLOTTE, N.C. — After a recent trend of sinkholes in the Charlotte area, including one near Bank of America Stadium in Uptown, many are wondering just how common sinkholes are in the Queen City.
Here's a closer look and explanation of how weather can impact the ground below.
A side-by-side comparison of a sinkhole in Florida versus one in North Carolina shows the potential and severity of Florida sinkholes.
A stark difference between the two is due to the geological composition of Florida, where the underlying bedrock is limestone and prone to collapsing by groundwater, leading to the formation of sinkholes.
A UNC Charlotte geology professor explained how the bedrock in the Carolinas impacts the formation of sinkholes in the Charlotte area.
UNC Charlotte geology professor Andy Bobyarchick said our bedrock in Charlotte is typically more resistant to large sinkholes.
"Our bedrock is what we call metamorphic rocks, and these are rocks that have been buried deep in Earth subjected to high temperatures and pressures," Bobyarchick said. "Many of our rocks have a lot of silicate minerals. And so, what that does is give us soils that are fairly high in clay content. And these soils tend to be impermeable or have to have low permeability."
Bobyarchick explained sinkholes in Charlotte can be mapped back to underground gold mines near the stadium in Uptown, which he said dates back to the 1800s.
"What happens over time is that the supports in those excavations -- which typically would have been wooden in composition -- decay and collapse, and that removes the support from the ceilings," Bobyarchick said. "And when those collapse, they often bring down the soil and rock above, and that creates a sinkhole."
Bobyarchick said the impact of extreme weather and human activities are typically the reason behind recent sinkholes in Charlotte.
"If you're in a drought situation, we're going to want to extract more groundwater than we might normally do, and that has the same effect as the fill and drain of an extreme weather event," Bobyarchick said. "You're going to lower the groundwater table, and that's going to weaken any voids in the rocks above. That's most appropriate for karst topography, but it is one of the possible effects."
The top causes of sinkholes include:
- Drought followed by heavy rain
- Weather erosion of soluble rock
- Changes in groundwater level
- Leaking pipes flush out soil
By using the knowledge of geology and climate zones, he said they can predict where sinkholes are likely to form and what the impacts could be in the Charlotte area. Sinkholes in the Carolinas, except the coastal zones, tend to have minor impacts.
Contact KJ Jacobs at kjacobs3@wcnc.com and follow him on Facebook, X and Instagram.