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Data based on field observations made during the summers of 1955-61 substantiate the belief that angle of slope is the most significant factor in determining the type of ground pattern which regionally or locally features arctic terrain.

The factors of influence in any arctic terrain ground pattern are texture of regolith, type and thickness of vegetation mat, amount of surface and subsurface water, thickness of active layer, and angle of slope of the ground surface.

The angle of slope and texture of regolith determine surface and subsurface drainage to a large extent, and thus control the water loss from the area. The amount of water in the ground, in turn, plays a large role in determining the type and amount of vegetation that can grow in the area and, hence, the thickness of the vegetation mat. The vegetation mat, in turn, pretty well determines the thickness of the active layer. It is most thick (deep) where the mat is very thin, or absent.

It was determined that equidimensional ground patterns, circular frost scars, hummocks, ice-wedge polygons, and sorted stone nets develop on slopes of less than two degrees. With increase in slope to four degrees, these patterns become elongated, but not aligned nor continuous, i.e.-not stripes. Further increase in slope to six degrees is featured by such linear features as stripes (both sorted and non-sorted), and by development of steps. Steps become much more pronounced on steeper slopes, and solifluction lobes characterize slopes in excess of eight degrees.

Some changes in slope are very common and very local, so that a regional pattern peculiar to a slope of two to four degrees will be modified by a pattern of the locally developed steeper slope.

Once one knows the significance of the different types of ground patterns, he can do an excellent job of determining terrain conditions of an unknown area from good air photos of that area.

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Proceedings of the Iowa Academy of Science





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©1962 Iowa Academy of Science, Inc.



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