The spatial distribution of the topographic change polygons across the conterminous United States reveals some notable regional differences and patterns of change. Overall, there is a decided concentration of change polygons in the eastern United States, which can be partially explained by the greater population density as compared to the west.
Map of the 5,263 polygons that delineate areas of significant topographic change in the conterminous United States. Cut areas are those polygons that have a decrease in elevation, while fill areas are those with an increase in elevation.
The greater density of population centers in the east, as well as the greater length of settlement, has created significant requirements for road and other infrastructure construction. The aggregate materials needed for such construction came from the numerous quarries represented by the topographic change polygons. Other noteworthy characteristics of the regional geography of topographic change that are recognized from the conterminous United States map include:
A dense concentration of change polygons in the mountaintop coal mining region in central Appalachia (eastern Kentucky, southern West Virginia, and southwestern Virginia)
A distinct cluster of change polygons is found in the Iron Range in northern Minnesota
Large groups of change polygons representing surface coal mining operations in the Powder River Basin in eastern Wyoming
Large open pit gold mines are found as a collection of change polygons in northern Nevada
A concentration of very large open pit copper mining operations is represented by the cluster of change polygons found in southern Arizona
Higher densities of change polygons are located near the coastal California cities of San Francisco, Los Angeles, and San Diego; these polygons are primarily related to road construction and urban development in higher relief areas
Other more subtle features are still recognizable:
Change polygons in central Florida that represent landscape modifications from phosphate mining
A concentration of change polygons representing limestone quarries located along the escarpment at the southeast edge of the Edwards Plateau in south central Texas
A cluster of change polygons in eastern Wisconsin that represent limestone quarries in the Niagara formation; other polygons in this concentration, as well as in Minnesota, Iowa, Illinois, and Michigan, represent the numerous gravel and sand pits located in glacial deposits
A roughly aligned group of quarries and mines along the fall line in Georgia and South Carolina at the boundary between the Piedmont and the coastal plain
A string of change polygons that is roughly aligned along the route of the Erie Canal in central and western New York
Recognition of these differing regional patterns and features of topographic change from a small-scale map of the conterminous United States underscores the value of conducting the inventory across the full expanse of the 48 contiguous states.