Image Name                   :  boug97mx
Boundaries                   :  Lat 12N to 35N ; Lon 239E to 287E
Color Scale, Upper (Red)     :  165 mgals and higher
Color Scale, Lower (Magenta) : -220 mgals and lower 
Data Max value               :  200.1 mgals
Data Min value               : -257.1 mgals
Illuminated from the         :  East 

  This is an image generated from 2'x2' terrain-corrected Bouguer gravity 
anomalies covering Mexico and surrounding areas.  Some interesting features
to note about this image are:

  The large blue/purple/magenta feature running NW/SE from the United States
to Mexico is a low induced by the depression of the North American Plate into 
the mantle by the Rocky and Sierra Madre Mountains.  These ranges 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) on the Southeast side of Cuba may be caused
by a continuation of the Cayman ridge into the Oriente area of Cuba.  It
stands out against the lows (magenta) caused by the Cayman trench
(south of Cuba) and the Old Bahama Channel (a western extension of the 
Puerto Rico Trench, north of Cuba).  In addition, the visible pin-points 
on Southeast Cuba and Jamaica are an artifact of the gridding routine on 
the synthetic data used in those areas.

  The sheer drop in the gravity field off of the east coast of the United States
is caused by a corresponding drop in the bathymetry, marking the edge of the 
continental shelf.  Similar behavior is seen off of the West coast of Florida
and the North coast of the Yucatan Penninsula.

  The low (blue/magenta) running along the west coast of Mexico, Guatamala and
El Salvador is caused by the Middle America Trench, with bathymetry 
over 3300 feet deep.  This trench marks the subduction of the Cocos plate under
the Caribbean and American Plates.

  The complicated structures seen in the gravity field of the Caribbean area 
are due to a complex system of tectonics around the Caribbean Plate.

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

das/dgm 4/14/97