An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and greenhouse periods, during which there are no glaciers on the
6:16
5:16
6:39
5:49
34:44
5:51
6:20
45:57
6:14
35:38
6:39
16:54
6:31
27:35
6:40
6:12
35:01
5:50
34:55
6:02