The Mount Baldy sand dune in Michigan City, Indiana was already pretty interesting, as far as sand dunes go.
At 123 ft. tall, the "wandering dune" is the tallest dune on the south side of Lake Michigan, moving a little each year as living dunes do. Already tourist attraction, visitors would relax on the beach, take a dip in the lake, and if they were feeling spry, take a sprint up to the top of Mount Baldy to enjoy the Chicago skyline from its delightfully high vantage point.
Its popularity with view hunters was eventually what made the dune go rogue. The marram grass that stabilized the giant pile of sand was eventually ruined by hundreds of human feet, and the slowly shifting "living dune" became a disturbingly fast moving pile of sand, headed directly for the park's parking lot.
The park service made the obvious moves—they close the dune off to visitors and replanted the grass. They crossed their fingers and hoped that the vegetation would do its job and slow the moving mountain, but before the marram could root properly, something totally unexpected and still unexplained happened—the dune ate a six year old boy.
The boy had been walking across a dune when a deep hole appeared out of nowhere beneath his feet, swallowing him quickly and completely. After 3 harrowing hours, the boy was located and rescued, scared and scratched up, but otherwise fine. As relief from the happy ending to a close call permitted, park rangers and scientists alike turned their attention to the 11 ft. deep hole that seemingly appeared out of nowhere.
No one had seen anything like it. With no water beneath it washing away its base, it's no ordinary sinkhole phenomenon. Since the incident in 2013, geologists and other researchers have tried just about everything to discover the cause of the sinkhole, which has been followed by two more, equally large and unexplained pits opening up on the surface of the dune. So far, the bizarre geological events remain a mystery.
