Top of the Rock sinkholes could reveal another cave system

Four sinkholes were discovered at Big Cedar Lodge’s Top of the Rock golf course on Friday morning and their sudden appearance could point to a yet undiscovered cave system, according to Bass Pro Shops Director of Conservation Martin MacDonald.

The largest sinkhole measures roughly 60-by-80 feet and over 35 feet deep, according to an executive with the engineering firm working to assess the situation.

All four holes were near a driving range beyond player areas, and they have since been fenced off to protect the public, said Gary Pendergrass, a principal with GeoEngineers Inc. in Springfield. He said golf play has not been impacted and that heavy rains in the past week have likely caused the sinkholes above karst topography.

“We want to ensure the safety of the guests down there, but they are still using the driving range and still using the golf course,” Pendergrass said.

Pendergrass and MacDonald said the sinkholes appear to have stabilized because there was minimal caving of the soil walls over the weekend with heavy rains hitting the area periodically. Pendergrass said the holes have not changed significantly since they were discovered around 5:30 a.m. Friday morning.

“We think we are at pretty much on the bedrock surface at the bottom of the hole right now,” he said of the largest sinkhole.

The collapses are thought to have filled in around the bedrock, and no new sinkholes are expected in or around the course, though GeoEngineers is continuing to monitor the situation.

“We see this all the time in southern Missouri,” Pendergrass said. “We’ll be doing a more complete investigation to really characterize all the sinkholes and how they interconnect with the caves on site. After that is done, we’ll be making recommendations to Bass Pro on options for stabilization and proceed from that point.”

MacDonald said over the next week or so GeoEngineers representatives would work with the Missouri Department of Natural Resources to determine the cause of the collapses and the best course of action moving forward. He said there is speculation a previously unknown cave system could be in the area because those monitoring the situation believe the water that was feeding into the sinkhole is now on the floor of an underground cave Bass Pro officials have called the Johnny Morris cave since discovering it about 12 years ago.

“There may be a cavern down there,” MacDonald said, adding that would be consistent with what geologist who have studied Lost Canyon cave have said previously. “There is much excitement from our founder and the geological team as to what might be there.”

MacDonald said there are no estimates on costs to repair the holes yet.

In late April, Top of the Rock hosted the second annual Bass Pro Shops Legends of Golf at Big Cedar Lodge.