Geologic Implications of Magnetic Surveys — Malahoff and Woollard 
285 
greater, the points of inflection on the profiles 
across the dipoles mark approximately the center 
of the anomalous body. Lenticular magnetic 
gradients defining dipoles persisting for long 
horizontal distances, such as the one striking in 
an east-west direction north of Mauna Loa, are 
interpreted as being due to intrusive rock in 
major crustal fractures. On this basis, the mag- 
netic anomaly field of Hawaii can be subdivided 
as follows: 
a. Dominantly east-west striking primary rift 
zones probably representing intrusions derived 
from considerable depths that are occupying 
primary fractures in the crust. 
