Study: Rotting trees caused mysterious holes in huge dunes

(AP) — Mysterious holes that forced the closure of a massive dune at an Indiana national park after a 6-year-old boy fell into one and nearly died were caused by sand-covered trees that left cavities behind as they decayed over the years, researchers have found.

Fungi on the covered trees formed a sort of cement that allowed the sand to keep its hollowed out shape as the wood decayed and collapsed inward, leaving holes more than 10 feet (3 meters) deep in the dune known as Mount Baldy at the Indiana Dunes National Lakeshore, according to a study published in December by Erin Argyilan, who heads Indiana University Northwest's department of geosciences.

The popular dune has been closed except for small ranger-led tours since the July 2013 rescue of the Illinois boy, who was trapped under sand for more than three hours.

G. William Monaghan, a senior research scientist at the IGS, said he hopes to have its completed study to the Park Service by Aug. 1.

Mount Baldy, which is a popular attraction at the national park along the Lake Michigan coast near Indiana's border with Michigan, formed about 4,000 years ago and moves faster than most coastal dunes.

Argyilan said similar holes have been reported in migrating dunes at the Oregon Dunes National Recreation Area in Florence, Oregon, and Silver Lake State Park in Mears, Michigan, but the holes at Mount Baldy provided the first opportunity to directly study them.