According to ScienceDaily, ice ages occur every 100,000 years. They are made up of extremely cold periods, glacials, during which thick ice sheets bury vast areas of North America, Europe and Asia, and warm periods, interglacials, when the ice melts.
The Earth has seen several ice ages since its formation, but the most recent glacial began in the Pleistocene era and ended about 10,000 years ago. This cold period was named the Wisconsin glaciation after scientists found evidence of it in Wisconsin. Scientists believe that the Earth is currently experiencing an interglacial period that is expected to last approximately 10,000 years.