The longest cave system in the world harbors a secret, one that a Franklin & Marshall College professor and his students have been working to uncover for the better part of four years.
“We’re hunting for what is known as the Lost River,” Visiting Professor of Geosciences Tim Bechtel said of his work at Central Kentucky’s 52,800-acre Mammoth Cave National Park. “There is a known flow-path through the Mammoth Cave system that takes water in a direction that is completely unexpected.”
Bechtel and F&M students have searched Mammoth Cave three times since 2011, including a trip last November, gathering evidence on the whereabouts of the Lost River using various geophysical imaging devices.
Until the late 1950s, the park was home to what was believed to be a series of independent caves—Flint Ridge Cave, Crystal Cave, Mammoth Cave, Colossal Cave and Bedquilt Cave. As explorers began finding passages that connected the caves, two spelunkers discovered a slot in a Mammoth Cave wall. They wriggled through the narrow opening into a large passage with a river. They later had trouble finding the slot they had stumbled upon. It remained a mystery until the early 1980s, when a University of Kentucky researcher conducted a dye-tracing test in a sinkhole expecting the water to flow in an easterly direction. Instead, it flowed west toward the Green River.
Sometime around 2008, one of the original spelunkers contacted Bechtel and asked him to search anew for the Lost River. Bechtel was quick to agree, noting the historical and scientific significance of the waterway.
“It’s a piece of the history of cave exploration that has stayed a mystery more than 50 years now,” he said. “It’s also part of a scientific mystery concerning how the plumbing system in Mammoth Cave works.”
During an expedition last summer, Bechtel and geoscience major Leah Houser ’16 used a micro-gravity meter to take readings at five-foot intervals along the passage. The highly sensitive device, about the size of a toaster oven, can be used to locate voids beneath the surface, in this case a tunnel carved into rock by fast-moving water. Houser is analyzing the data in one of F&M’s Hackman laboratories to determine where, beneath the passage, the river might flow.
“There are places where you have to climb and other places where you have to wriggle on your belly, and so we had the micro-gravity meter on a sled, gently pushing it along,” Bechtel said.
If their data provides a clue to the Lost River’s location, Bechtel and Houser said they would return to the cave passage and continue their search.
“If we find a gravity-low in an appropriate spot, then we have to get in there and have people wiggle in every possible little crack,” Bechtel said.