| | The Ultimate Ice age Dog Breeds Information Guide and Reference |
 | | The earliest well-documented ice age, and probably the most severe of the last 1000 million years, occurred from 800 to 600 million years ago (the Cryogenian period) and it has been suggested that it produced a Snowball Earth in which permanent sea ice extended to or very near the equator. |
| | The present ice age began 40 million years ago with the growth of an ice sheet in Antarctica, but intensified during the Pleistocene (starting around 3 million years ago) with the spread of ice sheets in the Northern Hemisphere. |
| | The timing of ice ages throughout geologic history is in part controlled by the position of the continental plates on the surface of the Earth. |
| www.dogluvers.com /dog_breeds/Ice_age (2008 words) |
