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Exploring The Science Behind Missouri’s 16,000-Plus Sinkholes

 Sinkholes create localized variations in topography at the Stemler Cave Woods Nature Preserve.
Alex Heuer
St. Louis Public Radio
Sinkholes create localized variations in topography at the Stemler Cave Woods Nature Preserve.

In early May, about one-third of the water in the 17-acre lake at Lone Elk Park was drained in the matter of a weekend. The culprit: a sinkhole the size of an SUV.

The occurrence came five years after a sinkhole opened at a nearby spot.

According to the Missouri Geological Survey, the state has about 16,000 sinkholes — some reaching depths of 100 feet. Blame its topography. More than half of Missouri’s surface is made up of carbonate bedrock and limestone, which are prone to dissolution.

“With time and a significant amount of small bits of acid in the rainwater and various other forms of water, it gets down into the rock, dissolves part of it, and gets into cracks and fractures that were previously there through roots or earthquakes and various things,” said Missouri Geological Survey geologist Jeremiah Jackson. “Over time, [water] widens up those cracks, creates a cavern, and slowly the soil starts to creep into there and, over time, creates a bowl shape and sometimes a collapse.”

Missouri is home to about 16,000 sinkholes.
Missouri Geological Survey
Missouri is home to about 16,000 sinkholes.

Jackson joined St. Louis on the Air to discuss the science behind Missouri’s many sinkholes. Chris Naffziger, historian and archives researcher for the St. Louis Recorder of Deeds, joined the discussion to share how St. Louis was developed upon such porous and uncertain terrain.

“Some of the most iconic and beautiful neighborhoods in St. Louis — Benton Park, Benton Park West, Gravois Park, Dutchtown, Tower Grove East, Fox Park — those neighborhoods are some of our most treasured neighborhoods in St. Louis. I wouldn’t ask for them not to have been built on, but yeah, there’s a lot of sinkholes,” Naffziger said.

“First thing I always do when there’s a sinkhole report in the news is I go straight to Compton and Dry’s Pictorial St. Louis from 1876, and of course, what was there? There was a sinkhole back in 1876,” he said.

Naffziger said that the 1876 map is a good thing for prospective homebuyers to check, though he added that there’s no reason to be too concerned or worried about buying land in St. Louis today.

“These sinkholes were filled in over 100 years ago. Your house is safe,” he said. “It is just kind of a great story about how tens of thousands of St. Louisans live on top of a cave system, and at one point, those caves were very easily accessible from the surface.”

For those seeking more information on the sinkholes, caves and mines in Missouri, Jackson recommends the Missouri Geological Survey Geosciences Technical Resource Assessment Tool.

In Missouri, Sinkholes Are A Natural Feature — Here’s Why

St. Louis on the Air” brings you the stories of St. Louis and the people who live, work and create in our region. The show is hosted by Sarah Fenske and produced by Alex Heuer, Emily Woodbury, Evie Hemphill and Lara Hamdan. The audio engineer is Aaron Doerr.

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Emily is the senior producer for "St. Louis on the Air" at St. Louis Public Radio.

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