Despite the use of ground-penetrating radar and substantial data gathering, scientists still don't know what is causing the holes. To ensure the public's safety, Mount Baldy ? including its parking lot, trail and the beach in front of the dune ? will remain closed to all vehicular and pedestrian access.
"The continued development of these holes in the dune surface poses a serious risk to the public," says Acting Superintendent Garry Traynham. "Our first obligation must be to the welfare of our visitors."
The Environmental Production Agency (EPA) conducted a survey using ground penetrating radar and identified anomalies below the dune's surface. Scientists from the National Park Service, Indiana University and the Indiana Geological Survey are still working to answer how these holes form.
According to scientists, the holes are often short-lived, remaining open for less than 24-hours before collapsing and filling in naturally with surrounding sand.
Scientists will launch a more comprehensive investigation into the dune this summer, which will include mapping openings, depressions and anomalous features, using multispectral Ground-Penetrating Radar (GPR) and coring to learn about the dune's internal architecture and detailed GPR and coring of anomalies identified in the EPA report.
During the investigation, the park's resource manager will continue planting marram grass where native dune grass used to grow. The grass's extensive root system holds sand in place and may help prevent future holes from materializing.
All other beach access areas in Indiana Dunes National Lakeshore are currently open. Visitors are asked to stay on the Established trails to prevent erosion and subsequent resource damage.