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Physiographic Regions of North America

In the pre-production phase of our lab's work on the maps for the upcoming second edition of Rivers of North America, one of the first data processing tasks that I undertook was to go through various sources' information on the physiographic regions of North America and delineate their boundaries, since we were asked that each map indicate demarcations that show the approximate boundaries of physiographic regions that a river or its watershed traverses. These regions were also defined on the maps found in the book's first edition; however, I quickly decided against using those same boundary lines when I noticed that the original lines had been based on a source that often used otherwise-arbitary international borders to define physiographic boundaries. A quick glance through additional sources made it quite clear that, for example, the 49th parallel does not actually divide the Northern Rocky Mountains from the Canadian Rockies, or at least certainly not from any geological or ecological standpoint.

The map on this page shows the results of almost a month's worth of work that I put into drawing a new set of physiographic region boundaries that, among other things, smoothly transition across international borders. This was done by georeferencing several different maps (one each for Alaska, Canada, the United States, Mexico, and Central America), then manually digitizing the lines in Adobe Illustrator. This allowed me to easily combine physiographic regions in different countries that otherwise coincided with one another (often with the only difference being the name assigned to it in a given country). Some region "mergers" were easier to decide on than others, but I was ultimately pretty happy with the end result, as was the book's editor, who approved of the changes and gave us the go-ahead to use them in the maps to come.

Sources

  • Arbingast, S. A. 1975. Atlas of Mexico. Austin: Bureau of Business Research, University of Texas at Austin.

  • Bostock, H.S. 1967. Physiographic Regions of Canada. Ottawa: Geological Survey of Canada.

  • Fenneman, N.M. and Johnson, D.W. 1946. Physiographic divisions of the conterminous U. S. Reston, VA: U.S. Geological Survey.

  • Marshall, J.S. 2007. The geomorphology and physiographic provinces of Central America. Central America: geology, resources and hazards, 1, pp.75-121.

  • Wahrhaftig, C. 1965. Physiographic divisions of Alaska. Washington, DC: United States Government Printing Office.