What were the major glacial ice ages over time?
Evidence from the geologic record shows that ice ages have occurred relatively few times in Earth’s history, with the first known large-scale ice age taking place approximately 2.3 billion years ago. (In the last about 670 million years, ice ages have occurred less than 1 percent of the time.) Geologists believe there have been five major ice ages over geologic time. The following lists the occurrences:
1.7 to 2.3 billion years ago (Huronian Era, Precambrian)
850 million years ago (Cryogenian Period)
670 million years ago (Proterozoic Era, Precambrian)
420 million years ago (Paleozoic Era, between the Ordovician and Silurian Periods)
290 million years ago (Paleozoic Era, between late Carboniferous and early Permian Periods)
1.7 million years ago (Cenozoic Era, Quaternary Period, Pleistocene epoch)