Four maps show the North American distribution of four principal types of rock: sedimentary, volcanic, plutonic and metamorphic rock.

• 
  Metamorphic rock
• 
  Plutonic rock
• 
  Sedimentary rock
• 
  Volcanic rock

• 
  North American terrain
• 
  North American rock types

Home: http://pubs.usgs.gov/imap/i2781/

Image: http://pubs.usgs.gov/imap/i2781/i2781_c_low.pdf 144 dpi, encoded to 72 dpi JPEG, compressed slightly to fit within Wikipedia 2MB limit.

Source: English Wikipedia, original upload 15 April 2005 by SEWilco

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