The Ice Cycles

Since about 800,000 years ago, the Earth has experienced a rather regular alternance of advancing and retreating glaciers. There is a major cycle of about 100,000 years; during the entire length of the cycle, the ice cover slowly expands until it reaches a peak. At the peak, glaciers cover most of Canada down to the Great Lakes, Iceland, Scandinavia and the British Isles. In the Southern Hemisphere, part of Chile is covered, and the ice of Antartica covers part of what is now the Antartic Ocean. The snowline changes by 1,000 meters in altitude from the warmest to the coldest periods during the cycle. There are also smaller cycles withing the 100,000 year cycle. These shorter cycles have a lesser effect on the ice cover and last 23,000 to 41,000 years. Please see the evidence by clicking here ! (from the Hartwick Geology Department).

After the ice cover has reached the maximum (in volume) during the 100.000 year cycle, it is observed that, in a matter of a couple of thousand years, the temperature rises to its highest levels and glaciers retrteat to a minimum. The last ice age (lasting 100,000 years) ended about 14,000 years ago. Since then glaciers have retreated to the smallest extent; in the last few thousand years, a mini ice-age has been underway.

This page was produced by Gianfranco Vidali.