Ice Age

An ice age is a period of long-term reduction in the temperature of Earth's climate, resulting in an expansion of the continental ice sheets, polar ice sheets and mountain glaciers.

There have been at least four major ice ages in the Earth's past. Outside these periods, the Earth seems to have been ice-free even in high latitudes.

Glacial Age is another term for Ice-Age.

It is not certain exactly what causes Ice Ages, but scientists have put forward theories that include the earths varying distance from the sun over time, volcanism, the amount of different gases such as methane in the atmosphere, variations in the suns energy output and even the effect of the impact of meteorites crashing into the earth.

In the last great ice-age, glaciers and ice covered Great Britain right down to Sotuhern England.