Since the start of the present ice age about 2.5 million years ago at least how many severe glacial periods have there been?
Channeled Scablands Channel Scablands sometime before 1.5 million years ago. Because of the fragmentary nature of older glaciofluvial deposits, which have been largely removed by subsequent Missoula floods, the exact number of older Missoula floods, which are known as "Ancient Cataclysmic Floods", that occurred during the Pleistocene cannot be estimated with any confidence. As many as 100 separate, cataclysmic Ice Age floods may have occurred during the last glaciation. There have been at least 17 complete interglacial-glacial cycles since about 1.77 million years ago, and perhaps as many as 44 interglacial-glacial cycles since the beginning of the Pleistocene about 2.58 million years
Late Cenozoic Ice Age commenced with Greenland becoming increasingly covered by an ice sheet in late Pliocene (2.9-2.58 Ma ago). The evolution of the Paranthropus occurred 2.7 million years ago. 2.58 million years ago was the official start of the Pleistocene Glaciation, the current phase of the Late Cenozoic Ice Age. Throughout the Pleistocene, there have been glacial periods (cold periods with extended glaciation) and interglacial periods (warm periods with less glaciation). The term stadial is a rough equivalent of the term glacial period. And interstadial is a rough equivalent of the term interglacial period. The oscillation between glacial and interglacial periods is due