As the ice breaks up on the rivers during the spring thaw in northern Maine, ice jams can build up to massive proportions. This video, shot in April 1991 on the Saint John River in Allagash, shows how dangerous ice jams can be.

One minute people are standing on the bridge, laughing and carrying on, and the next minute they're screaming and running for their lives, as the ice floe plows into the bridge and carries it away.

[YouTube video posted by Louie Pelletier III]