Environment & Science
7:32 am
Wed May 7, 2014

Scientists will work this summer to find the cause of mystery holes on Mount Baldy

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.

Drive on I-94 just outside of Chicago between Gary and Michigan City, Indiana and you might catch a glimpse of the massive sand dunes that make up the Indiana Dunes National Lakeshore. Tucked between coal plants and steel mills, the dunes are as high as 200 feet, stretching along the southernmost tip of Lake Michigan. 

Park Ranger Bruce Rowe started working at the national park thirty years ago.

“Most of the dunes at Indiana dunes people don’t recognize as dunes because they’re hiding under an oak forest,” Rowe said.

Rowe says the dunes were formed some 14,000 years ago, and most of them are now covered in forest.

But one dune at the park is different. Mount Baldy is, well, it’s bald. It has no beach grass to speak of, just a couple scruffy-looking trees struggling to survive. Mostly it’s just a big pile of beach sand.

Rowe says that’s partly because of its popularity. About 200,000 people visit the park each year. Rowe says almost all of them want to get their feet on Mount Baldy.

“For generations people climbed up and down Mount Baldy, had a wonderful time, and along the way may have helped damage it in a small way as well,” he said.

The park didn’t take the damage too seriously until last July.

That’s when six-year-old Nathan Woessner was investigating a small depression in the sand in an area that was blocked off for restoration. The depression suddenly gave way, swallowing him deep into the sand.

Rescuers had to dig down 11 feet into the sand to get Woessner out. Rowe says the child was injured but has now fully recovered. 

“We certainly don’t want to blame a six-year-old boy for seeing a hole just outside the official area and wanting to investigate it. That’s one of the reasons why the entire dune in the area is now closed, so that something like that doesn’t happen again,” Rowe said.

“The sort of misunderstanding that’s been out there is that the ground suddenly opens up and swallows people. It definitely is not a man-eating dune,” Erin Argyilan said. She’s a professor of geosciences at Indiana University Northwest.

“In most cases what we can do is we can walk up and we can see the structure of a hole and it’s been less than a foot across in diameter," Argyilan said. “They seem to have a pretty solid structure to them but they fill in rapidly.”

Argyilan was doing a wind study on Mount Baldy the day the hole opened up. She says at the time, she really could not believe what was happening. Holes that are narrow and deep enough to swallow a small child don’t just open up like that in the sand. It contradicted everything she knew about how dunes are structured.

“I called every geologist who would talk to me and the response was pretty much the same: That can’t happen, never heard of that happening, it cannot happen, something else must have happened,” she recalls.

But what is that something? Since last July, three more holes have formed and collapsed within the dune. Scientists still have no idea why.

Argyilan says their best guess is that the holes are caused by decomposing trees that have been buried under the sand dune for nearly a century.

She recently spoke with Oregon residents who told her they’ve seen the same thing happen in a system of sand dunes on the Pacific coast. That it may be happening in other dunes is an interesting development. Argyilan says it doesn’t appear anyone has conducted any scientific research on these holes in Oregon yet.

She is joining other scientists this summer who will conduct an extensive research project to try to figure out just what’s going on with these dunes.