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.
Interesting Facts about Ice Ages. 1  The current interglacial period that the Earth is in is called the Holocene period. 2  Most of Canada was covered with ice just 20,000 years ago. 3  An ice age can occur if the global temperature drops just a few degrees for a long period of time.