310 
PACIFIC SCIENCE, Vol. XX, July 1966 
trends paralleling the Hawaiian Ridge probably 
are geologically older. Although data are 
available only for the eastern end of the 
Hawaiian Ridge, they support the concept of a 
progressive development of the Hawaiian Is- 
lands along a major fault or fracture zone. 
However, because the strike of east-west mag- 
netic anomalies crosses the Hawaiian Ridge 
without interruption (Fig. 9), there is little 
question that the Molokai Fracture Zone has 
played an important role in the development 
of the islands lying east of Molokai. Certainly, 
some of the Hawaiian volcanoes appear to have 
formed where tectonic elements of the Molokai 
Fracture Zone have intersected with tectonic 
elements of the Hawaiian Ridge. All the mag- 
netic anomalies on the islands of Hawaii, Maui, 
Kahoolawe, Molokai, Lanai, Oahu, Kauai, and 
Niihau apparently have developed from intru- 
sions into crustal and upper mantle rift zones 
which are continuous for long distances. 
Save for one major exception — the Koolau 
caldera anomaly on Oahu — most of the anom- 
alies indicate normal polarization and the pres- 
ence of intrusive rock similar to peridotite. In 
no case does the topographic effect bias the 
anomaly picture indicating that the anomaly 
control is from intrusives at depth. 
Because of the consistency and the lack of any 
discordance in the magnetic anomalies, it is 
highly unlikely that the Hawaiian Ridge devel- 
oped through any mechanism of horizontal 
drift of the crust from a single volcanic center, 
as was postulated by Wilson (1963). 
ACKNOWLEDGMENTS 
The magnetic survey and the analysis of the 
data were made possible by funding under a 
grant from the National Science Foundation 
(nsf Grant gp-2256). 
The authors are grateful to Mr. Kenneth E. 
Culler who wrote the section on aircraft and 
instrumentation, and who served not only as 
pilot of the Stinson airplane, but also as an ob- 
server on board the uscgs ship "Surveyor.” In 
connection with the latter, special thanks are 
due Admiral H. A. Karo, Director of the U. S. 
Coast and Geodetic Survey and Captain R. 
Jones, of the "Surveyor.” 
The authors would also like to acknowledge 
the assistance of Dr. John C. Belshe, who pro- 
grammed the reduction of the data obtained 
on the "Surveyor.” 
Special mention must be made of Mrs. Bev- 
erley M. Malahoff and Mr. Theodore Bryant 
who reduced the data and aided in the inter- 
pretations of the magnetic anomalies, and of 
Dr. William E. Strange who was responsible 
for setting up all the interpretative techniques 
into machine computer language. 
Finally, the authors wish to acknowledge the 
cooperation of Professor Vernon E. Brock, 
Chairman of the Department of Oceanography 
of the University of Hawaii, and that of Cap- 
tain Lee O. Gregg, of the Institute research 
vessel "Teritu,” in carrying out seaborne mag- 
netic work off the island of Oahu. 
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