The Ice Age

          A million of years ago, the whole northern half of the earth was in the ice grip of the long ‘winter’ we call the Ice Age.
The earth is very old, at least four billion years old, scientist says. During its long history its climate has changed many times. About a million years ago was one of those times.  Summers in the North become too short and cool to melt all the snow that fell in winter.

          Year after year and century after century, the snow piled up. It got thicker and thicker. Snowfields in Canada came to be thousands of feet deep at their centre. The great weight of the snow turned the lower layers to slide ice, and the ice began ever so slowly to move outward at the edges. The masses of ice joined to form a vast ice sheet, or glacier, which crept southward. The moving ice bulldozed its way along. It chopped of the tops of hills it road over, gouged out valleys, and shoved tons and  tons of soil ahead of it. It buried millions of square miles of grass land and forest.

          Before it reached temperatures worm enough to stop it, the ice had covered half of North America. In time, the earth wormed up again. Once more plants could grow where the ice had been, and animals could make their home there. But the Ice Age was not over. After a long, long time, the earth again grew colder. Again an ice sheet came down from the north. This ice, too, finally melted away. Twice more ice spread over the land, then melted back. The last melting time began only 11,000 years ago. It is barely 8,000 years since the last glacier age in Minnesota melted away and left the ’10,000 lakes.’