644 
the part, west of the Kermadec and Tonga deep-sea troughs (see 
fie. 1), i.e. exactly the part which GERLAND °), with respect to its 
mn 
ess EN 
Bismarck IS. ~~ 
Tasmania 
Big dan me Boundary-line between the southwestern and the central 
part of the Pacific Ocean. 
structure, as the south-western part of the Pacific, contrasts to the 
north-eastern part, which 1 shall call the central part. MarsnHaLL *) 
also admits as the south-western border of the main (true, great or 
central) Pacifie a line drawn along the Kermadec and Tonga troughs 
and from there along the north side of the Fiji archipelago, the 
New Hebrides, the Salomon Islands, etc. 
Depressions, such as are found in this south-western part of the 
Pacific, appear to have been chiefly caused by crustal movements 
of opposite direction, so that a sabsidence in one part of the region 
is more or less compensated by an upheaval in other parts. In this 
south-western part of the Pacific one finds, besides indications of 
1) G. GERLAND, Vulkanistische Studien I. Die Korallen-inseln vornehmlich der 
Südsee. Beiträge zur Geophysik II, p. 29, 1895. 
2) P. MARSHALL, Oceania, Handb. der reg. Geologie VII. Heft 2, p. 28 and 32, 
1911. 
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