THE NEW ZEALAND 
JOURNAL OF SCIENCE 
AND 
TECHNOLOGY. 
Vol. IV. Wellington, April, 1921. No. 2. 
THE GEOLOGY OF WESTERN SAMOA. 
By Dr. J. Allan Thomson, F.G.S., F.N.Z.InsL, |?ii:eet(^ I)Qminion 
Museum. / ^ 
t, JUN28 1921. 
Contents. 
Introduction. 
The Historic Volcanoes. 
The Prehistoric Volcanoes. 
Lava-tunnels and Water-supply. 
Volcanic Rock-types and Mineral Resources of Samoa. 
Sedimentary Rocks and Coral Reefs. 
Further Exploration. 
Bibliography. 
Introduction. 
Six weeks’ residence in Western Samoa in October and November, 1920, 
with travel mainly round the coast-line of Upolu and the eastern side of 
Savaii have enabled me rather to appreciate the difficulties in the way of 
geological exploration in Samoa than to make many original observations 
of value. The difficulties lie in the climate, which renders w r alking and 
hill-climbing arduous, in the denseness of the tropical bush, and in the 
paucity of roads or tracks leading to the interior mountains. As many of 
the papers dealing with the subject are in German, and are not readily 
accessible to English readers, I have deemed it useful to collect all available 
information and present it in detailed form, adding my own few observations. 
I have to thank Dr. G. Angenheister for the loan of several German 
publications on the eruptions of Matavanu. 
The Samoan Islands lie between latitudes 13° and 15° S., and longitudes 
169° and 173° W. There are four main islands—Savaii, Upolu, Tutuila, 
and Tau ; and the smaller islets of Apolima and Manono, in the Apolima 
Strait, between Savaii and Upolu ; Nuatele and other small islets off the 
east end of Upolu; Aunuu, off the east end of Tutuila; Ofu and Olosega 
and a number of reefs making with Tau the Manua group ; and Bose Island, 
a coral island far to the east of the latter. From Savaii to Tutuila the 
islands have a linear disposition in a direction from west-north-west to 
east-south-east. Along this line Savaii has a length of forty-seven miles 
4—Science. 
