Background color for WARNING safety signs, labels, and tags. Marking hazardous parts of machines with may cut, crush, or otherwise injure. Emphasizing hazards when enclosure doors are open or when gear, belt, or other guards around moving equipment are opened or removed, exposing unguarded hazards. Marking exposed edges of
Bibcode:1995GBioC...9..377C. doi:10.1029/95GB01107. An ice age is a period of long-term 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.
1 There have been at least five major Ice Ages (or glaciations) in Earthâs history. 2  Earth has been ice-free, even in the high latitudes, for about 85% of its history.  The first Icehouse Earth occurred at about noon on the 24-hour geologic time scale (about 2.5Ba).