| Summary: | Many more depressions formed when buried or partly buried isolated blocks of glacial ice melted, causing the overlying materials to slump down. Geologists refer to these depressions as kettles. Kettles are also found in areas that were not covered by thick stagnant ice, but here they are generally much smaller and resulted when isolated blocks of buried ice melted. Today, kettle lakes, commonly known as prairie potholes or sloughs, are located in the depressions between the hummocks. In places, the insulating blanket of debris on top of the stagnant glacial ice was so thick that the cold temperatures of the ice had little or no effect on the surface of the ground. Trees, grasses, and animals established themselves on the debris on top of the stagnant ice. As conditions gradually stabilized, water collected in lakes in depressions on the debris-covered glacier. Most of the water in the lakes actually came from runoff from local precipitation rather than from meltwater from the glacier. Precipitation at the time was much greater than it is today, probably between 25 and 50 inches of rainfall a year, and the mean annual temperature was a few degrees cooler than it is today. Surrounding the lakes and streams, the debris on top of the stagnant glacier was forested by spruce, tamarack, birch, poplar, aquatic mosses, and other vegetation, much like parts of northern Minnesota today. This stagnant-ice environment in North Dakota 10,000 years ago was in many ways similar to stagnant, sediment-covered parts of certain glaciers in south-central Alaska today. Fish and clams as well as other animals and plants thrived in the lakes. Wooly mammoths, elk and other large game roamed the broad areas of forested, debris-covered ice. Prehistoric people may have lived on the insulated glaciers in North Dakota 10,000 years ago without realizing the ice lay only a few feet below. If they did realize it, they probably accepted it as a normal. Eventually all the buried ice melted, and all the materials on top of the glacier were lowered to their present position, resulting in the hilly areas of dead-ice moraine seen today. North Dakota's Mountainous Areas: The Killdeer Mountains And The Turtle Mountains It is at least somewhat peculiar that the Killdeer Mountains, Turtle Mountains, and several other features in North Dakota are called "mountains."The idea is likely related somewhat to scale. When viewed by a person who has recently traveled over eastern North Dakota, the features certainly are impressive, but what might have they been named if the settlers had come from Montana or Wyoming? Besides the Turtle Mountains and Killdeer Mountains, many other places in North Dakota bear the name "mountain." The town of Mountain in Pembina County was settled by Icelanders in 1873. Mountain is situated on the former shoreline of glacial Lake Agassiz, and the view to the east from there, over the Red River Valley, is impres- 536 2001-2003 North Dakota Blue Book
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