Researchers continue dune collapse investigation
By Amy Lavalley Post-Tribune correspondent August 14, 2014 12:38PM
A geological probe, for taking core soil samples, sits on Mount Baldy Thursday as researchers give an update on what is causing holes to form in the large dune. The smaller vehicle nearby is an all-terrain vehicle. | Sun-Times Media
For more on the research into Mount Baldy in the Indiana Dunes National Lakeshore, as well as pictures of holes that have formed in the dune and video from last year’s research, visit http://www.nps.gov/indu/parkmgmt/mount-baldy-dune-investigation.htm.
Updated: September 16, 2014 6:26AM
MICHIGAN CITY — More holes are developing on Mount Baldy even as researchers are gathering information to determine what’s causing them.
Three of the primary researchers gathered Thursday atop a cordoned-off section of the dune in the Indiana Dunes National Lakeshore to discuss the most recent efforts to find out what’s causing holes to form in the 126-foot dune.
The dune has been closed to the public since July 12, 2013, when Nathan Woessner, then 6, of Sterling, Illinois, fell into a large hole in the dune. He was buried for 3½ hours in 11 feet of sand and eventually recovered from the ordeal, but the incident sparked an ongoing effort to determine why holes were forming in the ever-shifting dune.
The most recent effort started Monday and will continue through the middle of next week, using two types of ground-penetrating radar and a geological probe to gather data and soil samples so scientists can get a better idea of the dune’s internal structure. The work builds on radar data collected a year ago by the Environmental Protection Agency.
“What we’d like to try to do on the dune is understand what it looks like inside,” said Todd Thompson, assistant director of research for the Indiana Geological Survey.
Wednesday, as he moved equipment across the dune, a place he stepped developed into a hole more than 3 feet deep. In all, six holes have been documented on Mount Baldy in the past 13 months, including the one the Illinois boy fell into.
Most of the holes have been relatively small, about 2 inches in diameter, and soon fill back up with sand, said Erin Argyilan, an associate professor of geology at Indiana University Northwest.
She was at the dune doing research the day of Nathan’s accident, and has been helping with the work on Mount Baldy since.
“Right now one of the ideas we have out there is trees that could be buried under the dune,” shifting with the sand or decaying and creating the holes, she said, adding scientists are not excluding other possibilities. A house already has been discovered under the sand, and scientists said other structures might be found as well.
A 292-foot-by-984-foot segment of Mount Baldy is the focus of the work, and is the place where most of the holes, including the one involving Woessner, are located.
Researchers will never know the size of the hole the boy fell into because of the flurry of activity to rescue him, Thompson said, adding no one took note of the size of the hole at the time, and it was later filled in.
“We will do ground-penetrating radar there and at the other holes,” he said.
Some holes have been reported at a dunes recreational area in Oregon, Argyilan said, but they are smaller and do not fill back in. “We don’t know what is happening here yet.”
Core samples from the geological probe also will help determine what’s under Mount Baldy.
“It’s probably a relatively unique phenomenon but an interesting one. That’s why we’re here,” said G. William Monaghan, a senior research scientist with the Indiana Geological Survey, adding Mount Baldy has shifted about 400 feet to the south over the past 70 years. “Now the original shape of Mount Baldy from the 1930s is gone and you’re going to see a new Mount Baldy.”
Researchers said initial results of their work should be available in a few months, with a final analysis complete in about a year. The work, Thompson said, is being funded by a $90,000 National Park Service grant to Indiana University, which houses the Indiana Geological Survey.
At this point, there’s no timetable for the National Park Service to re-open Mount Baldy, which was partially closed for dune grass restoration when the holes began to appear.
“The National Park Service is very pleased to have this research going on. We want to let science do the talking before we make any decisions on reopening Mount Baldy,” said Bruce Rowe, the lakeshore’s public information officer.