Ice ages are times when the entire Earth experiences notably colder climatic conditions where the addition of snow consistantly exceeds melting. During an ice age, continental-size glaciers can cover considerable large regions of the earth. The polar regions become much colder than they are presently and there are noticeably large differences in temperature from the equator to the pole.

There have actually been a number of ice ages in the history of the Earth. Large glaciations occurred during the late Proterozoic (between about 800 and 600 million years ago), during the Pennsylvanian and Permian (between about 350 and 250 million years ago), and the late Neogene to Quaternary (the last 4 million years and includes the Pleistocene epoch).

There have been at least 4 major ice advances since the Pleistocene epoch (which began about 1.6 million years ago). Called the Wisconsinan, Illinoisan, Kansan, and Nebraskan, these glaciations refer to the southernmost limit of glacial movement in North America.

When scientists refer to the ice age, they are usually talking about the most recent glaciation, the Wisconsinan.

The Pleistocene ice age is important in human history because it is theorized that this was the time when Homo sapiens evolved and spread through most of the world. Water was stored in massive sheets of ice resulting in the lowering of sea level. This allowed our species to migrate from continent to continent by landbridges.

There are many discussions among scientists to whether or not we are entering global warming or just experiencing a warming trend before the next ice age. So, it is possible that our modern climate is simply a very short, warm period between glacial advances.

Many of the mountain valleys in the Alps have glaciers at their heads. When Swiss geologist Louis Agassiz examined the valleys around his home, he noticed that the debris near the glacier, clearly put there by the ice, resembled the debris further down the valley. In other words, the glacier had been further down the valley in the past. The only mechanism he could imagine was that it had been colder at some time in the past.

As he expanded his examination, he found similar debris all over Europe. He concluded that ice must have covered most of the continent at some time in the past.

Agassiz published his findings in his 1840 work Étude sur les glaciers, and in the 1847 work Système glaciare. In 1846, Agassiz moved to the United States and started looking for evidence of glaciation in North America. And he found his evidence, lying all over.

Evidence for ice ages occurs throughout the geological record. A massive ice sheet covered large parts of the Gondwana continent through much of the Paleozoic Era, and a controversial (but plausible) "Snowball Earth" theory suggests that the Earth was completely covered by ice several times during the Precambrian.

Historically, four main ice ages were thought to have occured during the last 4.5 million years or so, the Pleistocene epoch. As has been reported elsewhere, it is now known that continental ice sheets have advanced and retreated many more than 4 times during the Pleistocene. Depending upon how big your requirement for an "ice age" is, there have been as many as 45 of them. But these four episodes represent the largest glacial maxima that have left traces on the Earth, and are thus of the most interest to people studying the Earth's surface. Various names have been given these episodes, where they have affected different regions of the Earth:

Alps      | Europe      | North America | China  
Gunz      | Menapian    | Nebraskan     | Po-Yang
Mindel    | Elsterian   | Kansan        | Ta-Gu
Riss      | Saalian     | Illinoian     | Lu-Shan
Würm      | Weichselian | Wisconsin     | Ta-Li

To climatologists, it's all part of a continuous fluctuation of Earth's climate, and we happen to be in a relatively warm period at the moment. Relative to the recent past. Other periods of geological history were much warmer than now, and it's reasonable to assume there will be warmer periods in the future. Only human conceit has caused us to separate the last 10,000 years into its own epoch, the Holocene. When asked "when will the next Ice Age come?", it's perfectly reasonable to answer "We're in an Ice Age right now".

Ice Age (2002) is a children's film from 20th Century Fox/Blue Sky. Its computer animation, although adequate, is below the technical standard of excellence set by Shrek and Monsters Inc. That doesn't matter, though, because this movie is funny. Damned funny.

The action starts with the Scrat, a half squirrel half rat fella with a long, almost prehensile snout and a passion for acorns, voiced (ok, squeaked) by the director, Chris Wedge. The hapless Scrat, trying to bury his acorn, sets off a monster avalanche and global glaciation. For the rest of the film, the Scrat appears sporadically, with his acorn, peripheral to the action. Pay close attention to the Scrat when he appears, as he's the most consistently funny character. In the DVD bonus features, there's a short that tells another chapter of his life. hint

The actual story follows a talkative ground sloth (John Leguizamo) and a grumpy mammoth (Ray Romano)in their quest to return a lost human child to its tribe. The quest is compromised by a double-dealing sabertooth (Denis Leary) with a secret agenda. There's an interlude with a flock of dodo birds, proving why they are extinct, a vidoe-game action sequence of sliding through an ice cave (watch the kid's hand when they see the UFO buried in the ice), and a slightly contrived but visually fun lava-under-the-ice sequence.

Contrived is a good word for the plotting of the film. That should bother me more than it does. I've switched off movies in disgust that were better plotted than this. In defense of Ice Age, the story isn't the reason you're watching this. It's the throwaway lines that the kids in the audience don't get, the broad slapstick, the guffaw/scene ratio.

I give it 18 stars out of 23 on the Eponymous Sliding Scale. Go ahead and buy it, on DVD (the special features are fun), but only if it's on sale.

N-Wing says he doesn't think it's as funny as I say, and the rest of the film suffers in comparison to the Scrat scenes. He may have a point, and de gustibus non disputandum.

Log in or register to write something here or to contact authors.