ABSTRACT

In the last 1.5 million years or so, known in geological terms as Pleistocene, the Earth has gone through several cold periods, called collectively glaciations or ice ages. The common feature of all glaciations was that large portions of the Earth were covered by ice sheets. Each glacial period lasted for about 70,000-100,000 years, and at least four such glaciations alternated with interglacial periods of 10,000-12,000 years.