Scientists have discovered that in the past million years, glaciers have covered the Earth's surface on several different occasions. There have been several "ice ages" in the Earth's past, and twenty thousand years ago was Earths most recently recorded. Large blankets of ice covered a large majority of land, …show more content…
Much of North America was under ice. Seven-thousand years ago the glaciers had melted off and that marked the end of it. Because of the glaciers being such ancient history it is hard for scientists to obtain and interpret data. The study of glaciers and the ice age is relatively new. In Switzerland around 1800, rocks attracted geologists in developing the first ideas of the ice ages. They wondered why large smooth boulders, called erratics, were lying out of place in fields and forests. Charles Lyell argued that icebergs had placed them there. Two other scientists stated that the boulders in the valley floors were similar to those found in the glaciers of the Alps. Louis Agassiz, a Swiss scientist, proved that ice could do this. He showed other scientists of places where large