Study: Top of the Rock sinkhole likely connects to cavern

A report filed this summer by the Missouri Department of Natural Resources identified a leaking surface pond as a possible cause for the largest of five sinkholes and depressions developed May 21 at Big Cedar Lodge’s Top of the Rock golf course in Ridgedale.

The question remains as to whether the largest hole is connected to a known cave system underneath the development owned by Bass Pro Shops.

Although the June 17 state report stopped short of drawing that conclusion, Douglas Gouzie, director of the geography, geology and planning department at Missouri State University who visited the site May 28, said geological features in the immediate vicinity are good indicators of a possible connection.

“It’s a pretty safe assumption that there is some sort of connection, but the extent of that connection is the magic question,” Gouzie said.

Reports of water draining from the pond through the sinkhole on the course’s driving range combined with muddy water found on the floor of a cavern underneath, as well as the presence of a known collapse and nearby caves are good signs, he said, but not definitive proof the sinkhole and cave are a directly connected system.

“Odds are pretty good that’s the same stuff,” Gouzie said of the discharge found in the Top of the Rock attraction Lost Canyon Cave and Nature Trail.

If the sinkhole and caverns are connected, Bass Pro Shops founder Johnny Morris has visions for another geological attraction.

“If there is a cavern, that would really enhance everything we’re trying to do there,” Morris told Springfield Business Journal in a July interview, referencing the current cave tour, nature trail and Ancient Ozarks Natural History Museum at Top of the Rock.

At the time, he said the company was conducting seismic testing to determine where a potential shaft might be dug, likening potential development of a new cave tour to that of Blanchard Springs Caverns near Mountain View, Ark.

“That was really hard to access, so the Forest Service put in an elevator shaft down 200 feet and maybe about half-a-million people a year go there,” Morris added. “Maybe that’s something we can do.

“I’m kind of nuts about caves.”

Morris said the ecotourism opportunity of a newly discovered cave would take the lead over golf at Top of the Rock.

Gouzie, who took part in the onsite visit with Bass Pro Shops Facilities Manager Dan Hoy and representatives of the state DNR and private firm GeoEngineers Inc., said the answer likely would come from a pending report by GeoEngineers. The firm has been conducting geophysical studies for Bass Pro for a couple of months.

GeoEngineers principal Gary Pendergrass declined to comment via a company spokeswoman, and DNR spokesman Tom Bastian declined via email to comment on the findings of department staff.

Bass Pro Director of Conservation Martin Mac Donald said company officials were not aware of the state’s report until local media began reporting on it in early August.

He added Bass Pro would take the DNR report into account along with GeoEngineers’ findings.

“They‘ve got a lot of historical data from years of geologic studies, so we were glad to get their input,” Mac Donald said of the state’s work, led by geologist Joe Gillman and Peter Price, the chief of environmental geology with DNR’s Missouri Geological Survey.  “We’re putting our final recommendations together and still exploring things.”

Bass Pro officials plan to make an onsite announcement in the coming weeks with regards to future plans for the sinkhole.

According to the state report, the creation of Top of the Rock significantly altered the natural landscape of the area, with the northern area where the sinks occurred built on a filled-in collapse structure.

Gouzie said determining if the structure was filled in naturally over potentially hundreds or thousands of years, or if it was filled during the development of the golf course, is nearly impossible. He said the surface pond likely played some part in the development of the largest sinkhole, which measures 60 feet in diameter and up to 40 feet deep.

“Knowing the landscape is rife with sinkholes, anytime I see a pond on a hill I honestly figure it’s only a matter of time,” Gouzie said, adding there’s no precise way to determine if the sinkhole at Top of the Rock would have formed in two years or two hundred years because of the pond. “Geology doesn’t work well on human time scales.”

The state report advised the hole be filled to prevent further collapse and, if rebuilt, the pond would need a synthetic and clay liner. Mac Donald said the sinkhole has stabilized, and its presence isn’t affecting practice on the driving range.

“The wet weather may have actually worked in their favor,” Gouzie said, adding moisture retained by clay in the soil could have kept it from drying out and falling in.

DNR’s report states personnel did not observe muddy discharge at nearby Clark Cave – known to be connected to the Top of the Rock cave – but it noted staff also never entered the cave to closely inspect the floor.

About 15 years ago, Morris said he entered the Clark Cave.

“I was the first person to ever get into it, which was kind of a magical, fairytale feeling,” he said. “I start in there, saw a big hole, and thought to get some help. I get ahold of Jack Herschend, one of the brothers of Herschend Family Entertainment, who is a real spelunker, and a couple of his sons. They had all this gear, like rope ladders and jumpsuits. It was about a week later, and we went in there. It’s a beautiful, pristine cave. … We followed it for about 300-400 feet, and we came to an end because these formations had grown. You could sense the cave keeps going, because the air is rushing out and the spring is coming up. I was having these miner buddies make a passageway to get around that obstacle. They had been working in there for maybe a couple of months when that sinkhole incident happened.

“What that told us is it’s one cavern that’s connected. We’ll try to explore that.”

Editor Eric Olson contributed to this article.