During its lifespan the Earth has experienced a number of the ice ages, also called glacial ages.
The were times of extreme cooling of the climate where ice sheets expanded to cover large areas of land. Between ice ages there were warmer interglacial periods and we are now living during such a time.
Many factors have altered the Earths climate over time, including tiny periodic variations in its orbit, the orientation of its spin axis and the movements of the continents. Surprisingly, throughout much of the Earth’s history global temperatures were on average 5 ºC warmer than today and the poles remained ice free.
Evidence for ice ages come from geological features such as valleys cared by creeping glaciers, as well as polar ice cores which contain bubbles of ancient air that give us valued temperature information.
There have been at least 5 major ice ages since Earth’s creation:
- The first (and most well-established) ice age saw a ‘snowball Earth’ with ice and snow almost reaching the equator. This lasted for approximately 850-630 million years and happened around 2.3 billion years ago.
- The current Quaternary glaciation began 2.6 million years ago or so, the Earth is now in an ‘inter-glacial’ period with a relatively warm period within an ice age.
- The last ‘especially’ cold ice age ended approximately 10,000 years ago, where glaciers extended across much of North America, Europe and Asia, as well as spreading out from the Andes of South America and becoming thicker across Antarctica