Richard Lederach., age 12, of Rio Grande, N.J., far his question:

What caused the Ice Ages?

This is one of the mysteries that we have not solved as yet. After all, the science of modern geology is quite young. About 150 years ago, most experts were sure that our wonderful world was only atout 69000 years old. 9 tranne to say, it was the discovery of the past Ice Ages whici.. caused the experts to change their minds about the age of the earth. Around 1836, Louis Agassiz took a long look at the glaciers of his native Swiss Alps. The evidence he gathered showed that giant glaciers had pushed down over northern Europe tens of thousands of years ago.

In 1846, Agas siz came to North America, seeking more evidence of the ancient glaciers. Yes., he found their tracks throughout Canada., New England. Michigan, Minnesota, Iowa and Illinois. Here too.9 the mighty glaciers had crept down and receded at some remote time. We know now that the great glaciers of the Ice Age have come and gone many times in the past. They have crept down over North America and northern Europe four times in the past million years.

In fact, the last of these Ice Ages is still receding from the northern part of the world There is evidence thv~ our climate is getting gradually warmer as though we were in a long springtime following the long winter of the Ice Agee Alaska's glaciers are slowly shrinking and the tundra regions are now warm enough to encourage certain birds. This gentle spring changed however, is very slow and we are not likely to notice much change in a single lifetime,

We know that the climate must have been cooler during an Ice Ages for the heat of the summers was not great enough to melt the winter snows.  However, we do not know why the climate should become cooler.

One theory suggests that our sun goes through cooler phases during which less heat is poured upon the earth. Another suggests that, though the sun remains constant, there are t irm s when less of its heat reaches the earth. This could be because of floating debris in the earth's atmosphere:. Dust or carbon dioxide could be the culprit. Carbon dioxide is poured forth by erupting volcanos, in which case each Ice Age may have followed a period of volcanic upheaval.

Dust in the air could also come from volcanic eruptions. It could also be present in the empty spaces of the Solar System. Some experts have suggested that perhaps the entire Solar System from time to time passes through vast clouds of cosmic dust. Such a mass of dust p though not noticeable, might very well cut off enough of the sun's heat to cause an Ice Age. Though ire are not certain of the cause, we do know that Ice Ages have been coming and going since earth's early history. There were at least four big Ice Ages before the recent series in the last million years.