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The Pleistocene Ice Age
The glacial periods of the Pleistocene are the most recent and most familiar in popular science with many famous creatures including the woolly mammoth and sabre-toothed cat.
The Pleistocene dates from 1.8 mya to 10,000 yrs ago during which conditions fluctuated between glacials and interglacial periods. The different glacial periods can be distinguished by the deposition of different layers of drift from the base of glaciers.
The ice sheets were very extensive over the Northern hemisphere and to a lesser extent in the Southern hemisphere. The spread was greater in the Northern hemisphere because of the closer proximity of continental land masses for the ice to spread over. In total approximately 30% of the earths land area was covered in ice. Ice extended as far south as Bristol in the UK. The extent of the ice sheet can be seen in the maps below.
18,000 yrs ago the maximum depth of the ice sheet was 2-3.5 km thick over North America, Europe and Asia, and the 70 million km3 of ice present resulted in a 130 m drop in sea level. This caused the growth of continental terrestrial area, because the continental shelves were exposed.
Evidence for the flora and fauna of the Pleistocene can be found from many sources:
1. Animal carcasses frozen into the ice of Siberia and other glacial areas
· The number of frozen carcasses being discovered has decreased - at times in the past the number was high enough that more mammoth ivory was being sold than elephant ivory!
· The preservation can be of such exceptional quality that the stomach contents can be identified and it is reported that the meat of a mammoth carcass was once served at a scientific banquet.
Mammoth Dima, 7 months old. She died 40,000 years ago probably of starvation. Skin and hairs can clearly be seen on the carcass.
3. Tar pit deposits e.g. Rancho La Brea, California, USA
· Tar pits can be a very rich source of fossils as herbivores would come to drink at the pits after rain and would become trapped in the tar. Under their distress, carnivores would be attracted to the pits and also become trapped. This would further attract carnivores and hence the number of carnivores tend to outnumber the herbivores 10 to 1!
18 Reconstruction of mammoth trapped in tar pit, Rancho La Brea, California
4. Cave paintings
· Paintings made by ice age man tend to portray the larger herbivores hunted by man and the carnivores. Although a general picture is not produced, information on animal interactions is provided.
During the Pleistocene, both poles had significant ice coverage when compared to today’s poles
Elsom, D. (1998) Planet Earth. Marshall Publishing Ltd, London