Air Force bomb disposal crews were called to Yellowstone National Park on Friday afternoon to destroy an unexploded 105 mm artillery round used in avalanche control above Sylvan Pass.

Bombs used to trigger avalanches above Sylvan Pass in Yellowstone National Park typically explode as planned, but on Friday one that failed to detonate last winter led to the temporary closure of the road that runs over the pass.

There are at least 20 identified avalanche chutes above the pass that park crews must conduct avalanche control on during the winter months to ensure safe travel for snowmobiles and snowcoaches coming into the park via the east entrance and during the spring to make sure the chutes aren't going to slide while snowplows are working to bust through the snowpack and open the road for summer traffic.

During winter months, park crews have between 100 and 300 55-pound artillery rounds for use in avalanche control. Come summer, they mark the hillsides above the pass off-limits to hikers, just in case there might be a stray round or two that didn't detonate.

Well, on Friday afternoon crews found an unexploded ordnance round near the road. The route leading in from the park's east entrance was shut down while a bomb disposal team from Malmstrom Air Force Base was called in to destroy the ordnance.

To the best of Traveler's knowledge, the last time an unexploded round was found along the pass was in 2006 when a construction worker came across a 55-pound artillery shell. And then there was the time in 1995 a visitor came across another unexploded shell and, not knowing exactly what it was, took it all the way to a visitor center, oblivious to the very real possibility that it could have detonated at any time.