Ice age

For other uses, see Ice age (disambiguation).

Variations in temperature, CO₂, and dust from the Vostok, Antarctica ice core over the last 400,000 years

An ice age is a period when for a long time the temperature of Earth's climate is very low. This leads to an expansion of the continental ice sheets, polar ice sheets and mountain glaciers.

Ice age is a phrase coined for the period of extensive ice sheets in the recent Pleistocene period. We now know that ice ages have happened a number of times in the past, the greatest and longest of which took place in the Proterozoic era, before multi-cellular eukaryotes evolved.

Stages

Within an ice age, there are stages. The longer cold stages are called glacials or glacial periods. The shorter warm periods are called interglacials.

We are still, in a sense, in an ice age, because the Greenland and Antarctic ice sheets still exist. When speaking of the last two million years, the Pleistocene ice age, in the glacials there were extensive ice sheets over the North American and Eurasian continents. The last glacial ended about 11,000 years ago when the present interglacial started.

Many glacial periods have occurred during the last few million years, initially at 40,000-year frequency but more recently at 100,000-year frequencies. These are the best studied. There have been four major ice ages in the further past.

Other pages

• Snowball Earth
• Ice core
• Milankovitch cycle
• Orbital forcing
• Pleistocene

Other websites

• Cracking the Ice Age from PBS
• Climate patterns. [1]