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Ice caps generally abrade and erode the ground surface to such an extent that the preglacial topography is substantially altered. In areas where the rock resisted glacial abrasion or the ice was not as thick, the topography can merely be smoothed or streamlined leaving hillocks and bosses. These features are unsymmetrical, and slope more gently on the upstream side and more steeply on the downstream side of the ice flow. Many mountains ranges including the Adirondacks, Green Mountains, and White Mountains of the eastern United States were smoothed rather than scoured to level plains. In New England, the many granite bosses form a special type of topography called a mammillated surface.
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