Geologic Implications of Magnetic Surveys — Malahoff and Woollard 
299 
TABLE 4 
Analyses of Total Force Magnetic Anomalies Over the Island of Molokai 
1* 
2* 
3* 
4* 
5* 
North Molokai Volcanic 
Pipe Zone 
0.8 
14.0 by 10.0 
8 
12.4 X lO- 3 
South Molokai Volcanic 
Pipe Zone 
1.0 
13.0 by 09-5 
10 
6.9 X 10-3 
Southwest Molokai Volcanic 
Pipe Zone 
0.2 
4.8 by 05.6 
10 
7.7 X 10-3 
West Molokai Volcanic 
Pipe Zone 
0.3 
4.8 by 05.2 
10 
(reversed) 
13-9 X 10-3 
1* Name of feature. 
2* Depth to top of anomalous body below ground level in kilometers. 
3* Approximate horizontal cross section of anomalous body in kilometers. 
4* Vertical length of anomalous body in kilometers. 
5* Magnetization contrasts between anomalous body and surrounding rock in cgs units. 
along two rift zones, one trending east and the 
other northwest. 
The West Molokai shield is built up of 
basaltic lavas of the West Molokai series, and 
is cut by dikes which strike southwest. 
magnetic relations: Figures 10 and 24 
indicate that two elements of the Molokai 
Fracture Zone cross the island. The North 
Molokai Primary Rift Zone anomaly (Fig. 24) 
defines here a bifurcation in the strike of the 
Molokai Fracture Zone. Along the northern 
shore of East Molokai, the rift zone defined 
strikes slightly south of west, whereas along the 
northern shore of West Molokai, it strikes north 
of west. The Southwest Molokai Primary Rift 
Zone anomaly shows no change in east-west 
strike and appears to intersect the North 
Molokai Primary Rift Zone anomaly. This in- 
tersection occurs at the location of the North 
Molokai volcanic vent, which is defined geolog- 
ically and topographically by a caldera. 
Although there are numerous minor mag- 
netic anomalies over Molokai (Fig. 25), five 
major anomalies define five major centers of 
intrusion. Two of these appear as broad anom- 
alies on West Molokai and three as smaller an- 
Fig. 25. Total force magnetic map of the island of Molokai, based on aeromagnetic profiles flown at 
8,000 ft. Contour interval at 50 gammas. 
