The village elders were forced to face the facts. Each winter was harder and longer than the one before it. The herds had all migrated south, and were unlikely to come back. The glacier had advanced noticeably within their lifetimes, and it was only a matter of a few more seasons before it began toppling and ripping apart the half-buried old buildings just north of the camp. Leaving their ancestral home would be heart-breaking, and the journey ahead would be dangerous, but they'd have to go. There just wasn't any life left for them in Chicago.
An ice age is an extended period of time when the earth is cold, snow is frequent, and large glaciers cover much of the land.
The concept that the glaciers had once extended further than they do now has long been known to those who live in their shadow. The term Ice Age was coined in 1837. However, the theory that the earth had previously passed through one or more Ice Ages did not gain world-wide scientific acceptance until the 1870s.
- 2.7 billion to 2.3 billion years ago - the Huronian ice age, which followed the Oxygen Catastrophe.
- 850 to 630 million years ago - with the largest glaciations, this period is known as the Cryogenian, and may have resulted in a Snowball Earth.
- 460 to 430 million years ago - a minor ice age called the Andean-Saharan.
- 350 to 260 million years ago - the Karoo Ice Age.
- Technically, the earth is in the final stages of an Ice Age, one that reached it's peak 20,000 years ago during the Pleistocene epoch.
Within an Ice Age, there are periods of severely colder weather known as Glacials, and warmer periods known as Interglacials. Some data suggests that interglacials last roughly 12,000 years, sandwiched between 100,000-year glacials. This is noteworthy because our current interglacial, if indeed that's all it is, has been going on for the past 11,000 years. Sometime in the next several hundred years, we may see the earth cool and glaciers expand dramatically.
Alternately, man-made global warming may upset that pattern. One theory suggests we'd currently be in a glacial period if not for the environmental impact of agriculture (and later industry). Perhaps the Little Ice Age was a hint of what might have been.
The exact cause of ice ages is controversial and debated. Most likely there are several factors that contribute to it, but it's still possible that one or two factors are the most significant. If ice ages are caused by Milankovitch cycles or the orbit of the sun within the galaxy, then ice ages are predictable and scheduled. If instead the main cause is airborne debris from a supervolcano or meteor impact, then one may occur suddenly, and with little warning.
Obviously, during an ice age, the world gets very cold, and glaciers spread. Because so much moisture is now in frozen form, instead of being water vapor, the air becomes very dry. Sea level drops. Lakes will drain out. Land-locked seas and salt-water shallows will become Salt Flats, broken up only by pools of briny hyper-salinated water.
Animals begin to migrate further towards the equator, and as a result, more animals must compete for fewer resources. In the equatorial areas, life is short and bloody, a constant struggle for resources. This causes extinctions amongst lifeforms not well suited for the cold, or for the heightened competition.
In a way, this gives a kick-start to evolution, as the forces of natural selection become somewhat more pronounced. Not all species will be able to migrate ahead of the advancing cold, and only the individuals within the species who are best adapted to inclement weather will survive. This will include those with shorter limbs, smaller ears, and larger bodies. Increased overall size means a larger volume to surface area ratio, and thus less loss of heat. Likewise, proportionally smaller legs, tails, and ears also means less heat loss. Particularly hairy (or thickly feathered) members of the species will fare better as well. Those specimens who have such traits will survive, and pass these same traits on to their progeny.
The passage and growth of glaciers displaces boulders and rips apart mountains and cities alike. The Great Lakes were gouged out of the earth by the most recent ice age. The earth pushed ahead of the advancing ice form long wall-like hills called moraines, which mark the glaciers' furthest advance. Other geological formations associated with ice ages are drumlins and eskers, hills formed when melting glaciers deposit earth and gravel suspended in the ice; and kettles, deep round lakes formed by the melting of huge ice chunks.
Our ability to create shelter, clothing and fire are incredibly useful in an ice age. Should an ice age come suddenly (such as from a Global Superstorm, as seen in the movie The Day After Tomorrow), man too would be faced with moving to equatorial habitat, and harsh competition for resources.
Game and Story Use
- Facing an ice age in an After The End setting really ramps up the troubles and dangers the characters must overcome. It also helps make your setting feel more unique than just another Mad Max retread.
- In a science fiction setting where travel between worlds is feasible, the PCs might explore a cold planet. They may find the native life is well adapted with large shaggy bodies and tiny limbs, and huddles together in herds to stay warm.
- Intelligent life that evolved on such a planet may have similar traits. These aliens might be self-aware and quite smart, but lack of resources (and the proportions of their bodies) has prevented them from developing significant technology.
- Time Travelers who go back into the distant past to learn of the origin of man had best bring along cold-weather survival gear.
- As global warming makes the glaciers melt, someone discovers an out-of-place artifact amidst the crumbling ice shelf. It suggests a technologically advanced lost civilization that was wiped off the face of the earth by the Pleistocene ice age.