Image Name                   :  boug96al
Boundaries                   :  Lat 49N to 72N ; Lon 171E to 235E
Color Scale, Upper (Red)     :  180 mgals and higher
Color Scale, Lower (Magenta) : -180 mgals and lower 
Data Max value               :  233 mgals
Data Min value               : -231.5 mgals
Illuminated from the         :  North 

  This is an image generated from 2'x4' terrain-corrected Bouguer gravity 
anomalies covering the state of Alaska and surrounding areas.  Some 
interesting features to note about this image are:

  The large flat zone in the Northwest corner of the image represents
the area of the former Soviet Union.  No gravity measurements from this
area were available, so a synthetic surface was used here.  Tests
have shown that the effect of this synthetic data on the Alaskan geoid
is minimal.

  The Aleutian trench, where the Pacific plate meets (and subducts under)
the North American plate, stands out as an elongated feature of both highs 
(reds) and lows (magentas).  
  
  The Aleutian back-arc basin, appearing as a backward "C" curve of 
reds/magentas extending off of the Aleutian trench in the Southwest corner of 
the image.  While not generating an island chain, this feature is large and 
geophysically fascinating.

  The "bumps" seen in the Gulf of Alaska (south of the land mass) are
the effect of seamounts on the Bouguer gravity field.

  The large blue/purple area in Southeast Alaska and Northwest Canada
portrays the isostatic footprint of the Rocky Mountains in the Earth's mantle.

das/dgm 10/18/96