Image Description from historic lecture booklet: "The land waste and the land surfaces of the United States often resemble those found in a region of present glaciers. This is so widely true as to show that great glaciers once covered the face of the country. We are now to look at some of the proofs of these earlier glaciers. At the beginning of the period of cold, deep snows gathered and ice was formed on broad uplands of Canada. As the cold increased, the area of ice formation grew larger, and the ice also spread by flowing outward about its edges. The ice centers were not among high mountains, but the ice grew in thickness until, like a mass of pitch it was forced to flow by its own weight. It spread in all directions, and the south edge crept out over what is now the boundary of Canada and invaded the region of the United States. How far it reached can best be understood by studying the map. The line of its extreme limit, which geologists have traced with care, traverses the southern border of New England, crosses New Jersey, Pennsylvania, and southwestern New York, and then follows a crooked course north of Missouri and then runs northwest through Nebraska, the Dakotas and Montana. The ice outline had different forms at different times."

Original Collection: Visual Instruction Department Lantern Slides

Item Number: P217:set 012 008

You can find this image by searching for the item number by clicking here.

Want more? You can find more digital resources online.