In Ice Age: The Meltdown, a flood threatens the animals’ valley.
The 2006 sequel is built around the danger that warming conditions are melting the ice dam surrounding the valley. Manny, Sid, and Diego learn that the resulting flood could destroy their home, so they join the other animals in a race toward a safer location.
The disaster gives the sequel a different central threat from the first film. Ice Age focuses on migration during advancing cold, while The Meltdown uses melting ice and rising water as the reason the characters must travel.
The film also develops Manny’s relationship with Ellie and introduces her opossum brothers, Crash and Eddie. Those character stories unfold during the larger evacuation, making the flood both a plot engine and the setting for the group’s comic obstacles.