Answer: (1) Pleistocene
(2) early Permian
(3) Ordovician
(4) late Precambrian
Explanation:
The earth is presently in the middle of a glacial period (which is less intense now relative to 19,000 years ago) but this tells us that the Earth has an history of a period of glaciation in the distant past.
The episode of glaciation also known as the Ice Age is divided into different sub eras as stated above with differing characteristic properties.
Glaciation - is the process or time of covering with a glacier upon the earth, or the state of being glaciated.
The Ice Age is the era when there was the glacial phenomena.
Glaciers are systems of flowing ice that form where more snow accumulates each year rather than melts.
As ice flows, it moves and then erodes the surface of the land by plucking and abrasion. Sediment picked up during its movement is transported by the glacier and deposited where the ice melts. In the process described above, the landscape is greatly modified and the surviving species differs.
