Susie Good, Age 13, Of Lancaster, Penna.., for her question:
Haw far did the ice age glaciers reach?
A few generations ago, the experts thought that our world was about 6000 years old. Then they saw that some of the scars left by the ice age were at least a million years old. This led geologists to make other observations, and they now estimate that our old earth has had at least four billion birthdays.
In the past 500 million years, our earth has endured through several ice ages. About 200 million years ago.. An ice age gripped regions near the equator. Its glaciers spread through parts of india and africa, south america and australia. But the glaciers we know most about are those that spread through the northern hemisphere. They are recent geological eyents, for they came and went during the last million years.
We call such an icy event a period of glaciation. In the past million years, glaciers crept down frcc the north polar regions and receded four times. The glaciations were separated by inter glaciation periods of warm climate. So we can regard the entire period as four separate ice ageb or as one continuous ice age separated by warmer phases.
Each of the four invasions spread massive glaciers over much of North America and northern Europe. In North America, we name such glaciation for the state which
Marks the southern boundary of its ice sheets. There was the Nebraska ice age, the Kansas ice age, the Illinois ice age and the Wisconsin ice age.
About a million years ago, the icy glaciers of the first ice age reached as far south as nebraska.. Then came a long spell of warm weather and the ice sheets receded to the north. Some 700,000 years ago, the glaciers of the second ice age reached as far south as Kansas. The ice receded again and then crept down a third time, this time as far south as Illinois. After another warm phase, the glaciers of the fourth and last ice age spread south as far as Wisconsin.
At the same time, north= Europe was also held in the frosty grip of ice age glaciers. Here, too, the ice fields extended south and receded as they did in North America. However, in Europe, the four invasions were very much alike., and each time the glaciers covered more or less the same area.
Some of the phases between the glaciations were warmer than our present world's climate. Geologists suggest that we are now living in an inter glacial warm period which may be followed by still another invasion of glaciers, perhaps 50,000 years in the future. However., we cannot predict this with certainty, because no one knows what causes an ice age.