North America Tapestry of Time and Terrain

Through digital mapping and GIS (geographic information systems) technology, USGS has drawn together information from two different types of maps into a single digital tapestry. Embedded within this map are a geologic map of North America, compiled by John C. Reed of the U.S. Geological Survey and John O. Wheeler of the Geological Survey of Canada, and a shaded relief map, which was created by converting elevation data into a digitally-shaded map of the North American landscape. See http://nationalatlas.gov/atlasftp.html for digital versions of the underlying base maps.

This geologic map has been simplified from its original source map, in order to show patterns of rock age and distribution, and then reprojected to match the shaded relief map for a perfect image overlay. The resulting composite displays both the land surface and the ages of its underlying rock formations. This digital tapestry outlines the geologic story of continental collision and break-up, mountain-building, river erosion and sediment deposition, ice-cap glaciation, volcanism, and other events and processes that have shaped the continent over the last 4 billion years.

Although the Tapestry files themselves are not available as GIS data files, you may download PDF files of the map and obtain some of the digital coverages that were used to create the Tapestry of Time and Terrain.