Mysterious Holes in Mount Baldy Force Park Service to Keep Landmark Closed

The National Park Service announced Sunday that the mysterious holes that appear and vanish in the sands of Mount Baldy at Indiana Dunes National Lakeshore will keep the landmark closed indefinitely, according to The Associated Press. The rest of Indiana Dunes National Lakeshore - which hugs 15 miles of the southern shore of Lake Michigan - will remain open.

Two new holes that are about a foot in diameter and several depressions were detected on the north side slope. The holes in Mount Baldy are different from "sinkholes," which usually form from rock surfaces that dissolve over time because of water damage, and can grow large enough to swallow a car or house.

"We're seeing what appears to be a new geological phenomenon," said geologist Erin Argyilan, one of the investigators puzzled by the spectacle.

The holes remain in Mount Baldy for less than a day and then get filled naturally with sand.

Experts, including Argyilan, have combed the terrain for clues the holes' origin. Ground-penetrating radar and specialized GPS devices used to peek below the landscape still haven't come up with any answers.

Argyilan has been studying the base of Mount Baldy since mid-July, and first learned of these chasms when she heard a couple scream after their six-year-old son was engulfed by the sand. Rescue crew saved Nathan Woessner of Sterling, Ill. after a three-hour burial under 11 feet of sediment.

In August, a second hole was spotted nearby, this one about 10 inches wide and at least 5 feet deep, prompting further study.

Researchers speculate that decaying trees beneath the sand might be the source of the phenomenon. Human activity on the dunes and along the shore has led to erosion of Mount Baldy, and as a result, the 126-foot dune's sand has been drifting towards the south, possibly burying trees that are in turn rotting and creating holes beneath the surface.

Argyilan believes it is unlikely that this will occur in any other dunes which have been kept in a more natural state.

"This particular dune has a complicated history," she added.

National Park Service officials said they're preparing for a more thorough investigation of the dune this summer, including mapping of holes and depressions, use of special ground-penetrating radar and coring of samples of sand and organic matter. In the meantime, they will be planting new grass where the native vegetation once grew in the hopes that it will hold the sand in place and prevent new holes from forming.