“Climate change is having a dramatic effect on the ground.”
—Andrew Mitchell, British Conservative Member of Parliament
My wife Katherine and I were watching the news this week and hearing about yet another sinkhole, this one at the Summer Bay Resort in Clermont, Florida this past Monday. Fortunately nobody died in this one, but this past March in Florida, Jeff Bush fell into a sinkhole in his home and presumably died—his body was never recovered.
I’d heard of sinkholes before but it seems they’ve been on the news a lot more lately than they ever used to be. I know they’ve been around for many millennia, but anytime our planet changes its behaviour I get curious if it’s due even in part to global warming and climate change. So I decided to look into the science of sinkholes a little further.
A sinkhole by definition is any natural depression or hole in the Earth’s surface, and there are numerous causes. One of the natural processes that can contribute to their formation is erosion where somewhat soluble bedrock is gradually removed, often from percolating water. Another process is referred to as suffosion where material sitting on top of limestone gradually washes away through cracks and fissures in the limestone beneath it. This process is usually gradual but occasionally the weight of the material on top of the limestone leads to an abrupt collapse. The two sinkholes in Florida this year resulted from the process of suffosion. Of course, anything sitting on top of sinkholes when they collapse such as roads and buildings fall in as well.
Some of the manmade processes that contribute to sinkhole formation include mines that collapse and water mains that burst underground. But could manmade global warming be playing a part? Grenville Draper is a geologist at the Earth & Environment department at Florida International University and he states that record-level rainfall last month could be one possible trigger for the Summer Bay Resort sinkhole. As Draper told NBC news in a recent interview:
“I’m thinking the saturation of the ground makes the sand layer heavier, and this probably triggered the collapse of the sand into the cave.”
It also turns out that certain events such as a hurricane following a period of drought can trigger a series of sinkholes to occur, sometimes within minutes to hours of each other according to Jonathan Arthur, director of the Florida Geological Survey. This actually happened with Tropical Storm Debby back in June 2012. According to Arthur:
“It came across Florida after a period of drought where water levels in the ground were lower and then we had the massive influx of rain, over 20 inches in some areas, and that change in the climate and the groundwater levels triggered hundreds of sinkholes across the state over a very, very short period of time.”
Although Florida has had two high profile sinkholes this year, there are other U.S. states at risk as well including Texas, Alabama, Missouri, Kentucky, Tennessee and Pennsylvania, according to the U.S. Geological Survey.
So although natural processes create these geological processes, direct effects from global warming and climate change such as an increase in droughts, floods and hurricanes can also be contributing. Perhaps we should anticipate even more of these in the coming decades.
As if there weren’t already enough disasters we had to face with climate change as it is.