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Description: 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."

Description: Image Description from historic lecture booklet: "When a glacier enters the sea the water buoys the ice up, causing great masses to break off, forming icebergs. Other masses are broken away by undercutting along the water's edge. The bergs from Greenland rarely project 200 feet out of water, and most of them not more than 100 feet, but they are sometimes a mile or more across."

Description: Image Description from historic lecture booklet: "Ice bodies of the third class, as their name implies, are of vast extent and may even cover entire continents. Existing examples are confined to Greenland and to Antarctic regions. Others that have now vanished left unmistakable records over large portions of northeastern North America and northwestern Europe. The principal characteristic of continental glaciers are their vast extent, their comparatively level surface, and the prolongation of portions of their borders into lobes and even into well-defined streams, were the topographic and other conditions are favorable. The total amount of snow and ice on all land is perhaps as much as a million cubic miles. If this amount of ice were all melted and returned to the sea, it would raise its level about thirty feet."

Description: Image Description from historic lecture booklet: "When the glacier had melted off in the vicinity of the present Chicago and Detroit two points north of the divide, the eastern region about the Mohawk and St. Lawrence valleys, was still full of ice. It will readily be seen, therefore, that there were lakes gathered on the north. As the ice melted farther back these lakes became greater in size and often changed much in form. But in time the ice melted out of the Mohawk Valley in New York and the drainage of these glacial Great Lakes poured out between the Adirondacks and Catskills to the Hudson and the sea. Still later, the glacier melted out of the St. Lawrence Valley, and the Great Lakes came to their present levels and forms.

Description: Image Description from historic lecture booklet: "This kind of plain was made by the streams that came from beneath the ice as they wandered this way and that and dropped their load. Many such plains are found in the Northern states, and the process of their making may be witnessed at the margins of many glaciers of Alaska."

Description: Image Description from historic lecture booklet: "Every large snow-field is also an ice-field, for where snow accumulates to great depth and lies long upon the surface, it is changed to ice. the beginning of this change may be seen in the snow a few days after it falls, for it soon loses its light, flaky character and becomes granular, so that it feels harsh to the hand. The change is very distinct in the last banks of snow in the spring. They are made up of coarse grains (granules) of ice, sometimes as larges as peas. The change from flakes of snow to granules of ice is due, in part, to the melting of the snow and the freezing of the water. If there is much snow, it is compressed by its own weight, and after being compacted in this way, the freezing of the sinking water binds the granules together. By this and perhaps other process, the large part of every thick snow-field becomes an ice-field merely coated over with snow."

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