This boat was a vast piece of wood from a giant tree.
Once a part of a giant tree, the boat stood atop a series of crags within Ice Valley. During the days of the ice age, the valley was to undergo a great flood as the ice surrounding the valley was melting, causing all the animals within the valley to head for the boat. The boat, as a vulture known as the Lone Gunslinger put it, was the only means for the animals to escape the flood, though it lay past a series of geysers.
The herds of escaping animals reached the boat before the flood hit and began to board it at once: just as the floods began, however, the animals that were boarding rushed quickly to make it in time. The boat soon fell from the crags where it lay and fell into the waters, floating about until the flood waters abated as they were drained into the other end of the valley. All the animals aboard the boat stepped off and were glad to reach solid ground once more, save for an old molehog that claimed the boat as his own.
Behind the Scenes
The boat was initially intended to be an actual boat constructed by humans that had been left behind, but the directors of the second film had decided that there should be no mention of the humans at all in the film.