Significant Topographic Changes in the United States
Proximity of Topographic Change Areas to Other Features
The near-national extent of the topographic change dataset also allows for spatial comparisons, such as proximity of change polygons to roads and urban areas. Such comparisons have been done for the proximity of mines to roads and major cities for the five focus ecoregions. This figure shows the locations of the centroids of mining polygons within the five ecoregions and the locations of cities with a population of greater than 100,000 from the 2000 census.
The next figure compares the summary statistics of the distance from mines to the nearest major city (by ecoregion).
Note that the mines within the Northwestern Great Plains ecoregion are the farthest removed from major urban centers. The minimum distance from mines to the nearest road was calculated by intersecting the mining polygons with the national distance-to-nearest-road dataset.
The figure below shows the summary statistics for the distance calculations (by ecoregion). On average, the mining polygons are farthest from the road network in the Northern Lakes and Forests ecoregion. This may imply a less dense road network in the vicinity of the mines. Distance from mines to roads may also become important as mining areas are expanded. More road construction may be required as mining is expanded in regions that currently have a greater overall distance from mines to roads.