----------------------------Original message----------------------------
Dave is right about the DIP. Check out USGS map GP 1004-Z "Magnetic
Vertical Intensity" 1990.
There is a small description of dip in the lower left corner.
 
Gary Nebeker
USGS Earth Science Information Center - SLC
Gnebeker.isdres.er.usgs.gov  vox 801-524-5652