Image Name                   :  d96aleta
Boundaries                   :  Lat 49N to 72N ; Lon 172E to 234E
Color Scale, Upper (Red)     :  20 arcseconds and higher
Color Scale, Lower (Magenta) : -20 arcseconds and lower 
Data Max value               :  40.5 arcseconds
Data Min value               : -41.7 arcseconds
Illuminated from the         :  East 

  This is an image generated from 2'x4' E/W surface deflections of the
vertical 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, is visible but not prominent, due to it's 
primarily E/W shape (thus yielding strong N/S deflections).
  
  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 deflections of the vertical.

  The large "network" of fine lines filling much of Southeast Alaska
and Northwest Canada are due to the high-frequency changes in the
geoid and deflections, which are induced by similarly high-frequency terrain.

das/dgm 10/18/96