272 
PACIFIC SCIENCE, Vol. XX, July 1966 
TABLE 1 
Average Values 1 of Susceptibility (p) and Natural Remanent Magnetization for Rocks 
of the Hawaiian Islands 
NRM JlI 
NRM 1 2 p 
NRM p 
FORMATION 
(Tailing, 1963) 
(Authors) 
(Decker, 1963) 
Hawaii (tholeiite) 
11.0 
3.2 
Hawaii (olivine-rich 
basalt) 
5.0 
0.5 
Hana (E. Maui) 
17.31 
4.63 
— 
— 
Kula (E. Maui) 
137.30 
13.28 
100.0 
5.0 
Honomanu (E. Maui) 
0.96 
2.66 
1.0 
2.5 
Honolua intrusive rock 
20.0 
2.8 
Honolua (W. Maui) 
14.34 
2.74 
15.0 
2.7 
Wailuku intrusive rock 
1.0 
0.5 
Wailuku (W. Maui) 
8.19 
2.01 
10.0 
2.8 
Lanai 
5.88 
0.92 
East Molokai 
19.43 
2.13 
West Molokai 
13.22 
1.16 
Koolau dike rock 
(Oahu l) 3 4 
20.0 
3.2 
Koolau dike rock 
(Oahu 2)4 
2.0 
0.5 
Koolau (Oahu) 
3.09 
1.83 
5.0 
1.8 
Waianae (Oahu) 
2.67 
2.19 
— 
— 
Honolulu peridotite 
— 
— 
0.4 
Honolulu (Oahu) 
4.78 
3.92 
3.0 
3.2 
Koloa (Kauai) 
6.45 
1.24 
5.0 
2.1 
Napali (Kauai) 
4.21 
1.01 
5.0 
2.0 
Niihau 
— 
. — 
— 
— 
1 Values in cgs units by 10 -3 . 
2 As determined with an astatic magnetometer. 
3 Dike rock collected along Pali Highway (Oahu 1). 
4 Dike rock collected from Keolu Hills quarry (Oahu 2). 
lected from the island of Hawaii, representing 
both tholeiitic and alkalic basalts; 20 samples 
were collected from the island of Maui, repre- 
senting both intrusive and extrusive rocks; 30 
samples were collected on Oahu, and 10 on 
Kauai. All samples were collected from un- 
weathered outcrops and were oriented in the 
field. Susceptibilities of the rock samples were 
measured by using cores and a susceptibility 
bridge. The rock cores were bored in a direction 
parallel to the vector of the earth’s present mag- 
netic field in Hawaii, and intensities and direc- 
tion of polarization (whether normal or re- 
versed) were measured with the aid of a simple 
astatic magnetometer. 
Because the islands of Hawaii have been 
formed by the extrusions of numerous strati- 
graphically thin basaltic flows, whose magnetic 
properties appear to vary from flow to flow, 
the susceptibilities used in topographic reduc- 
tions and anomaly computations were averaged 
out for each individual volcano. The collection 
pattern followed, therefore, was one which 
would give samples representing as large a 
vertical section through a given volcano as 
possible. 
The susceptibilities for rocks on the island 
of Hawaii for all the volcanoes except Hualalai 
average 2.3 X 10“ 3 ± 1.0 X 10“ 3 cgs units. 
However, 80% of the rock samples have a value 
of 2.2 X 10 -3 0.5 X 10 -3 cgs units. The 
intensities of remanent magnetization average 
11 X 10 — 3 cgs units. As indicated earlier, the 
olivine-rich basalts collected from Hualalai 
Volcano had low susceptibilities of the order 
of 0.4 X 10“ 3 ± 0.2 X 10 -3 cgs units. The 
values adopted for all computations on Hawaii 
except Hualalai Volcano were 2.2 X 10“ 3 cgs 
