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.
View full size image. The Pleistocene Epoch is typically defined as the time period that began about 1.8 million years ago and lasted until about 11,700 years ago. The most recent Ice Age occurred then, as glaciers covered huge parts of the planet Earth.There have been at least five documented major ice ages during the 4.6 billion years since the Earth was formed â and most likely many more before humans came on the scene about 2.3 million years ago.he most recent Ice Age occurred then, as glaciers covered huge parts of the planet Earth. There have been at least five documented major ice ages during the 4.6 billion years since the Earth was formed â and most likely many more before humans came on the scene about 2.3 million years ago.