Image Name                   :  boug96us
Boundaries                   :  Lat 24N to 53N ; Lon 230E to 294E
Color Scale, Upper (Red)     :   75 mgals and higher
Color Scale, Lower (Magenta) : -300 mgals and lower 
Data Max value               :  153.4 mgals
Data Min value               : -351.3 mgals
Illuminated from the         :  East 

  This is an image generated from 2'x2' terrain-corrected Bouguer gravity 
anomalies covering the conterminous United States (the "lower 48") and
surrounding areas.  Some interesting features to note about this image are:

  The large blue/purple/magenta feature running NW/SE from Canada to Mexico
is a low induced by the depression of the North American Plate into the
mantle by the Rocky Mountains.  The Rocky Mountains are generally 
isostatically compensated.  The effect of the plate depression (a low) 
is larger in magnitude than the effect of the isostatic root of the 
mountains (a high), causing an overall low in the Bouguer gravity anomalies.

  The high (yellow/orange) snaking southwest through Minnesota and Iowa
is known as the "mid-continent gravity high".  This gravity high is the
result of dense masses which lie close to the surface. These masses lie
in an old rift in the North American plate.

  The sheer drop in the gravity field off of the east coast (as well as
west of the west coast of Florida) is caused by a similar drop in the 
bathymetry, marking the edge of the continental shelf.

  The larger "bumps" seen in the Pacific are the effect of seamounts on
the gravity field.

das/dgm 10/18/96