An 80-ton granite slab known as the Mysterious Hanging Boulder collapsed onto a walking path at the Polar Caves park in Rumney, New Hampshire, on October 18, 2026. The sudden failure destroyed a wooden pedestrian bridge on the final day of the park’s operating season, forcing a closure with an expectation to reopen in 2027.
For more than a century, the massive formation defied expectations of gravity. Opened to tourists in 1922, the boulder balanced precariously on three points against a granite wall while roughly 75 percent of its bulk hovered directly over the visitor walkway. Images shared by visitors after the collapse showed splintered wooden handrails and a blocked trail.
Park administrators confirmed that no injuries occurred during the incident. Because the structural failure happened on the last day of the season, the pathway was not occupied at the moment of impact. The site will be evaluated during the off-season before being reopened.
Geological Pressures Behind the Century-Old Collapse
The sudden descent of the granite block highlights the relentless pace of natural erosion. Joseph Licciardi, a glacial geologist at the University of New Hampshire, pointed to long-term exposure to wind, rain, and shifting temperatures as primary drivers behind the loss of stability. Water infiltration into fissures, followed by freeze-thaw cycles, gradually weakened the boulder’s three-point granite footing over its tenure as a tourist draw. Licciardi also noted that he had not examined the rock after the collapse and that the specific cause had not been determined.
An 80-ton rock dubbed the “Mysterious Hanging Boulder” that hung with three-quarters of its weight directly over hiking trails in New Hampshire fell on Sunday. | 🔗 https://t.co/sXXBs8tqtJ pic.twitter.com/gXqVZWhkQS
/https://i.s3.glbimg.com/v1/AUTH_da025474c0c44edd99332dddb09cabe8/internal_photos/bs/2026/D/3/pXBR2eT7Am9LIXlCVdTQ/d10d559b-5394-4221-b7a6-15325ec8dfe7.jpg "Photo: O GLOBO")
The physical landscape of the Polar Caves dates back far beyond the park’s twentieth-century establishment. The enormous granite boulders and subterranean cavities were deposited by a receding continental glacier thousands of years ago. Specifically, according to the Polar Cave Park, the granite stones characterizing the area were deposited by glaciers during the Ice Age about 11,000 years ago, within the White Mountains region that was covered in ice thousands of years ago. The park’s network of nine caverns, narrow passages like “The Lemon Squeeze” and “Fat Man’s Misery,” stone labyrinths, and an animal area were formed by prehistoric ice movements, alongside natural trails featuring approximately 3.2-kilometer routes guiding visitors through rock formations and natural areas.
| Feature | Details |
|---|---|
| Boulder Weight | Approx. 80 tons |
| Park Opening Year | 1922 |
| Date of Collapse | October 18, 2026 |
| Target Reopening | 2027 Season |
Echoes of Past Granite Collapses in New Hampshire
This structural failure immediately brought back local memories of another iconic geological loss in the state. New Hampshire previously lost the Old Man of the Mountain, a famous cliffside profile in Franconia Notch that collapsed on May 3, 2003. Both landmarks demonstrate how natural weathering processes eventually alter formations that human visitors view as permanent fixtures of the landscape.
Officials have not yet decided on the fate of the rock or potential alterations to the path.
