Click either map for a larger image: Geology
or Shaded Relief maps.
Through digital mapping and GIS (geographic information systems)
technology, we have 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.
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.