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PACIFIC SCIENCE, Vol. XX, July 1966 
Fig. 12. Map of the island of Hawaii showing location of visible and concealed faults. (From Steams and 
Macdonald, 1946.) 
b. Dipole centers associated with volcanic 
vents. It appears significant that all these vol- 
canic center anomalies are located on the axes 
of the principal longitudinal anomalies related 
to primary crustal rift zones, and that the latter, 
in general, do not coincide with secondary frac- 
ture systems. 
Some superficial rift zones, such as the south- 
west rift zone on Mauna Loa, do have an as- 
sociated magnetic effect ; however, most primary 
rift zone anomalies (Fig. 11 ), such as the east- 
west rift zone anomaly north of Mauna Loa 
and the Mauna Kea-Hualalai rift zone anomaly, 
do not have associated superficial features. Judg- 
ing from the magnetic depth estimates and sizes 
of the dipole anomalies, these primary rift zone 
