Nobody, especially Manny, believes any of that until the mammoth goes up top to stop Sid from doing something crazy to try to prove his worth. They then realize that the glaciers are indeed melting, and should those walls give way, the resultant flood waters would drown everything in the bowl-shaped valley. Accordingly, they all set out for a reported boat that's at the far end of the valley.

Along the way, the trio runs into Crash (voice of SEANN WILLIAM SCOTT) and Eddie (voice of JOSH PECK), a pesky duo of possums whose "sister" Ellie (voice of QUEEN LATIFAH) is unaware that she's really a full-sized mammoth. Manny's happy he's no longer the last of his kind, but the two clash, all as Sid tries to prove he can be a leader and Diego tries to overcome his fear of water.

As the group makes their trek, they must not only put up with their differences, but also two hungry sea monsters that lurk in the rising waters, as well as the inevitable collapse of the valley walls and the resultant massive flood that could sweep all of them away.

In that film, prehistoric humans were seen as the bearers (and forbearers) of some bad news for various animal species. One could have viewed that plot as an allegory for humankind driving various species to extinction in today's world, but on the surface, it was designed as a plot catalyst to help keep an unlikely trio of animal character "friends" on the move.

The same could be said for the plot here penned by Peter Gaulke and Gerry Swallow and overseen by returning co-director Carlos Saldanha. In it, global warming is causing the glaciers to melt, thus raising the immediate risk of a catastrophic flood should some mighty glacial walls give way.

As a result, our intrepid trio and an assortment of new characters set out for safety at the end of their valley where a rumored boat (or ark, if you will, in a bit of Christian infused elements including the eventual flood as well as a later trip to the Pearly Gates by one perpetually plucky if unlucky character) is said to exist.

Along the way, they deal with their various issues. Manny -- the dry-humored mammoth voiced by Ray Romano -- frets that he's the last of his species, but gets a surprise when he runs into Ellie (voiced by Queen Latifah in light bubblegum mode). Unfortunately, she thinks she's a possum and thus hangs out with her real marsupial brothers (voiced by Seann William Scott and Josh Peck).

Meanwhile, Sid the sloth (John Leguizamo) just wants a little respect (and gets more than he bargained for in a tribe of diminutive but copycat sloths in one of the film's cuter scenes) and Diego the saber-toothed tiger (Denis Leary) must deal with his fear of water which is timely considering the rising levels of such H2O.

Throw in some prehistoric sea monsters for added suspense, a flock of vultures that suddenly break into a modified version of the musical-based song "Food, glorious food," and the return of Scrat (the acorn-obsessed Charlie Chaplin of prehistoric squirrels), and the stage is set for a fairly entertaining road trip flick aimed at kids of all ages.

Although those who view the global warming angle as a political ploy might think otherwise, that part of the film thankfully isn't too heavy-handed, although the pending threat of peril (represented in various asides by cracks, leaks and falling debris from the glacial walls) and the eventual realization of that might be a little (or a lot) intense for younger viewers.

As was the case the first time around, the film works best when showcasing the fine details as well as the supporting characters. Beyond Scrat (again "voiced" by the first film's other co-director Chris Wedge) who mostly appears in his own, standalone but charming and/or funny vignettes, there are the aforementioned possum characters. Adhering to the old mantra of good things coming in small packages, those three characters are far more entertaining and even interesting than the main ones (and their accompanying emotional baggage) that again prove to be too lackluster for an offering such as this.

The animation -- while seemingly improved over the somewhat blocky look of the first film -- isn't bad or distracting, but still lacks the "Wow!" factor that usually accompanies the Pixar and "Shrek" films. Somewhat surprisingly, no humans are present this time around, although one can't help but think of their contemporaries' effect on the environment and reported increasing global temps while watching this story play out.

Of course, that will go over most kids' heads, as they'll only be interested in being entertained. In that simplest sense, the film should succeed with its mixture of action and comedy. I found it moderately entertaining and engaging, but wished all of it could have been as clever and enjoyable as its smaller moments and characters. "Ice Age: The Meltdown" rates as a 5.5 out of 10.