Corrected entry: All of the animals realize they are trapped in the valley unless they can get to "the boat" before the area floods. This begs the question - where did they come from that led them to the valley and why not just go back the other way instead of making the pointless trek to the other side?
Corrected entry: Ice melts from the outside in, so the dam should have melted at the same time as all the water behind it.
Correction: Yes ice does melt that way but the water behind the dam was most likely a river that had been blocked by the movement of a glacier. Ice dams did exist during the ice ages, some of them holding vast amounts of water and they still exist today in places such as Iceland. Here is some information on ice dams: http://en.wikipedia.org/wiki/Ice_dam.
Corrected entry: Near the beginning, where Sid threatens to jump of the ice cliff, Manny and Diego are shouting from the ground for him to come down. Then about a minute later it cuts to Sid up on top of the hill, and Manny and Diego are already up there. It took 10 minutes for Sid to get up there but it took Manny and Diego a minute.
Correction: There is nothing to indicate that it was only a minute later. Sid was obviously trying to put it off as long as possible, I think he was up to 2 and so many parts of a thousand. So it's not implausible that, since they knew their friend was in danger, they rushed up the cliff.
Correction: They've been there a long time. The path they took is now frozen.
MasterOfAll