280 
near the edge of the Hawaiian Deep, the as- 
sociated magnetic anomalies continue westward 
without interruption along the strike of the 
Molokai Fracture Zone. However, it is to be 
noted that there are some notable changes where 
this trend intersects that of the Hawaiian Ridge. 
North of Maui, as seen from Figure 4, the "Ha- 
waiian Deep magnetic anomaly" bifurcates 
into two distinct anomaly trends. One trend 
crosses the island of Molokai and continues to 
strike in an east northeast-west southwest direc- 
tion for at least another 600 km without any 
change in strike direction. The second trend 
strikes to the northwest, to merge into the 
anomaly defining the Koolau Primary Rift Zone 
of Oahu (Fig. 10). 
Two local high amplitude magnetic anomaly 
dipoles are superimposed on the Koolau Primary 
Rift Zone anomaly. One anomaly (1,400 gam- 
mas peak-to-peak) is located over the Koolau 
caldera on Oahu. The other anomaly (1,600 
gammas peak-to-peak) is located in the Kaiwi 
Channel and has no known geologic counter- 
PACIFIC SCIENCE, Vol. XX, July 1966 
part. Over the northwestern portion of Oahu, 
the Koolau Rift Zone anomaly merges with the 
Waianae Primary Rift Zone anomaly on the 
leeward side of Oahu to form a single anomaly 
trend striking in a direction parallel to the strike 
of the axis of the Hawaiian Ridge. As the south- 
ern end of the Waianae Primary Rift Zone 
anomaly terminates against the west southwest 
strike of the Molokai Fracture Zone anomaly 
belt, it appears to have been broken by transla- 
tional movement along the latter. This is the 
only notable instance of direct discordance be- 
tween the strike of the Hawaiian Ridge-oriented 
magnetic anomalies and the magnetic anomalies 
oriented parallel to the Molokai Fracture Zone. 
If the elongate primary magnetic anomalies 
represent crustal fractures invaded by mantle 
material, Figure 10 defines the "rift" zones. 
These were constructed along the inflection 
zones of the elongate magnetic dipole anomalies 
as marking the geographic location of the source 
of the anomalies. As will be seen, primary 
volcanic vents are marked by intense local dipole 
Fig. 7. Magnetic profile along line C-C (see Fig. 4) north of the island of Maui. 
