Anthony Carter, age 13, of Mascot, Virginia, for his question:
How much time has elapsed since the last Ice Age?
We might say that this time is still elapsing. Earth scientists say that the remnants of the last ice age still are lingering and dwindling here and there. What's more, they suspect that our geological period may be one of those interim warmer spells, sandwiched between two ice ages. If this is so, it would be very difficult to detect the exact year when the last ice began to merge its icy fingers with the next one.
In recent years, researchers have discovered some amazing evidence that sheds a lot of new light on the earth's geological past. Years ago it was possible to trace the paths of former ice ages, estimate their havoc and calculate their comings and goings. But predicting them was impossible because nobody had a sound idea about what caused them. It is just possible that the recently discovered evidence may be able to explain the ice ages as natural events in the global shiftings of the earth's crust.
This may or may not prove to be true. But the earth's surface shows us plenty of scars to estimate most of the details concerning the last ice age. It was the last of four such cold times to occur during the past million years. This Wisconsin¬Wurm ice age reached its peak about 100,000 years ago. In North America, its massive ice fields reached far enough south to claw out basins for the Great Lakes. Others reached into central Germany, covering much of Europe under icy glaciers a mile or more thick.
These glaciers clung to this territory for more than 50,000 years. Then about 40,000 years ago, a changing climate caused them to lose their icy grip. They started to wane and their icy edges began melting into streams of icy water,. The glacier centered on Labrador receded far enough to free the Great Lakes region about 36,000 years ago. Progress was slow, but after another 8,000 years, the ice had melted from most of New England.
The worst was the Keewatin ice cap, centered in Minnesota. It began a slow, stubborn retreat from this region about 15,000 years ago. In Europe, central Germany was freed about 17,000 years ago, though slushy melting ice persisted farther north.
How much time has elapsed for Thursday, January 27, 1972 through many centuries. The ice fields crushing Scandinavia lingered still longer and refused to retreat until about 13,040 years ago. The remnants of glaciers from the last ice age still linger on the central mountains of Greenland and in several Arctic regions.
Glaciologists keep careful progress reports on the remaining northern glaciers. Apparently their edges recede a few feet or inches, then often refuse to budge for several years. In general, they seem to be receding though with great reluctance. If this is so, our mild post glacial period is not about to decline. But until we know more about the causes of ice ages, nobody can predict the next one.