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PACIFIC SCIENCE, Vol. XIX, July 1965 
mgal going southeast into the interior. Project- 
ing from the coast the observed maximum 
gravity gradient of 20 mgal per mile would 
result in a + 300-mgal maximum at the cen- 
ter. Only one high is apparent from the data. 
Numerous rift zones are discernible trending 
in the northeast, north, west, and southeast 
directions. 
The Bouguer anomaly map of the Taiarapu 
Peninsula (Fig. 4) shows contours elongated 
in an east-west direction separated from the 
Tahiti-Nui anomaly by the + 205 mgal con- 
tour line. The lowest observed value was +189 
and the highest was +205 mgal. The maximum 
gradient was 10 mgal per mile, occurring on 
the northeastern end of the peninsula. Project- 
ing this to the southwest would give a maxi- 
mum value of +230 mgal at the center of the 
caldera, with the gravimetric center closely co- 
inciding with the given geologic position. Al- 
though the gravimetric data support the geo- 
logic locations of the caldera, they do not sub- 
stantiate the observed changes in lithology. 
According to the gravity data Tahiti-Nui is 
more basic than is Taiarapu Peninsula. 
Mo ore a 
Topographically Moorea is the complete op- 
posite of Tahiti, appearing in profile as a series 
of jagged peaks separated by moderately slop- 
ing valleys. The island is triangular in shape, 
measuring 10 miles on each side; and the high- 
est point, located south of the island center, is 
