Gravity Investigations on Leeward Islands-— KROENKE and WOOLLARD 
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lowest Bouguer anomaly value of +308 mgal 
was found at the northeast tip, and the highest 
value of +315 mgal at the southwest tip. The 
gravity gradient averages 10 mgal per mile and 
increases towards the southwest. The maximum 
Bouguer anomaly value at the projected center 
of the gravity high located to the south and 
west of Lisianski would be approximately 
+ 325 mgal. 
Pearl and Hermes Reef 
This large atoll is comprised of many small 
islets enclosing a low, coral-filled, shelf area. 
Only seven of the islets could be occupied, and 
these are located along the southern edges. A 
+ 276 mgal Bouguer anomaly value was ob- 
tained on the southeast reef, and values in- 
creased to +285 mgal to the southwest. The 
gravity gradient averages 5 mgal per mile. The 
contours (Fig. 4) indicate that the high should 
be found to the north and west of the location 
of the +285 -mgal station, with maximum Bou- 
guer anomaly values possibly as high as +305 
mgal 
Midway 
Midway I. is a large coral atoll. From mag- 
netic and seismic measurements the coral cap 
is estimated to be 1000-2500 ft thick (Harry 
Ladd, personal communication ) . The contoured 
Bouguer anomaly map (Fig. 5) shows values 
ranging from a low of +284 mgal on the south 
Fig. 4. Bouguer anomaly map of Pearl and Hermes Reef. 
