Scientists continue to search for the reason that holes open in the Mount Baldy sand dune at Indiana Dunes National Lakeshore/NPS.

Mount Baldy, a massive sand dune that is a popular attraction at Indiana Dunes National Lakeshore in Indiana, will remain closed indefinitely due to safety hazards.

Last July a 6-year-old boy was swallowed by a sink hole in Mount Baldy. The youth was rescued after being trapped for three-and-a-half hours.

Now lakeshore officials say that "despite the use of ground penetrating radar, and data gathering at two additional holes that have appeared since last July, scientists still don'™t know the cause of the holes at Mount Baldy."

Additional studies will be conducted this summer and might run on into the fall, a park release said, adding that, "to ensure the public'™s safety, Mount Baldy, its parking lot, trail, and beach in front of the dune will remain closed to all vehicular and pedestrian access while the investigation continues."

'œMount. Baldy is one of the most visited sites in the national lakeshore, attracting thousands of visitors each year,' said acting-Superintendent Garry Traynham, 'œbut the continued development of these holes in the dune surface poses a serious risk to the public. Our first obligation must be to the welfare of our visitors who are here for an enjoyable outing.'

Ground penetrating radar studies by the Environmental Protection Agency identified a large number of anomalies below the dune'™s surface, the park release said, but analysis by scientists from the National Park Service, Indiana University and the Indiana Geological Survey have not yielded answers on how these holes form. 

Additional holes and a number of depressions have been found during the ongoing investigation and continued monitoring of the dune. Scientists report that the holes are short-lived, remaining open for less than 24 hours before collapsing and filling in naturally with surrounding sand.

This summer scientists intend to map openings, depressions, and anomalous features, use multispectral Ground-Penetrating Radar and coring to develop a better understanding of the overall internal architecture of the dune, and perform detailed GPR and coring on some of the anomalies identified in the EPA report.

During the research work, the park'™s resource managers will continue planting marram grass on portions of Mt. Baldy where the native dune grass used to grow. The extensive root system of the grass holds sand in place and may also help prevent holes from opening up on the dune'™s surface.

All other beach access areas within the national lakeshore are currently open and visitors are asked to stay on the established trails to prevent erosion and subsequent resource damage.