Ice age is the gap of time in which great portions of the earth remain spread with ice sheets. Ice age is a feature of weather and environment where there is a prolonged decrease in earth's climatic temperature. Due to this there is enlargement of ice sheets of continents and the poles and glaciers.

Ice Age and Glaciations:

Ice age describes the intervals of time on 2 scales that are separate. It is used to expound very cold and lengthy intervals in the earth's history when the glaciers receded or progressed. The intervals could span from some 10 to 100 million years. An ice age can also relate the intervals of 10 to 1000 years which are fairly shorter and when the glaciers were in their prime. These intervals of time which are short are referred to as glaciations. Ice age is also used to depict the chief glaciation that took place in Eurasia and North America.

Various Glaciations:

Over the last billions of years of the Earth's history there has been several progressions and retreats of glaciers. The glaciations have been distributed in 4 major time intervals which have occurred in the following periods of Proterozoic Eon, Ordovician and Silurian Eon, Pennsylvanian and Permian Eon and Neogene to Quarternary. In the past 2 billion years there have been about 60 glacial progresses and retreats. It is believed that we are living in an ice age even today. The proof is the existence of ice sheets like Antarctica and Greenland.

An ice age can be caused by several factors of which one can be,the changes of the atmosphere induced by greenhouse gases.