Indiana Dunes National Lakeshore

Lindsey Smith / Michigan Radio

A popular summer spot in the Indiana Dunes National Lakeshore is closed indefinitely. Scientists are trying to figure out the mystery of why some dangerous sinkholes have been developing in the dunes.

National Park Service Collection

A popular spot in the Indiana Dunes National Lakeshore will remain closed for the summer because of the mysterious appearance of holes in the 126-foot sand dune's surface.

Last July, a six-year-old boy was almost killed when a collapsing hole at Mount Baldy buried him in sand. Since then, two more holes and some depressions have been found.

So far scientists cannot explain why. That's despite the use of ground-penetrating radar and research analysis by scientists from the National Park Service, Indiana University, and the Indiana Geological Survey.

Scientists are getting ready for a more comprehensive investigation of the sand dune this summer.