404 
VeRBERK, in his report on the Moluccas '), was the first to contrast 
these two tracts geologically. On the basis of somewhat different 
geological conceptions the present author’) did the same in 1912. 
Thus the latest geological history of the Hast-Indian Archipelago 
teaches us that the two first-named shallow seas or shelves form 
parts of larger tracts, which have recently, anyhow after the 
Pliocene, maintained their stability and, putting it geologically, have 
behaved “‘continentally”, whereas all the others belong to unstable 
portions or geosynclines, which were orogenetically active in the 
same time. 
It thus appears that in the East-Indian Archipelago adjoining 
portions of the earth’s crust have behaved very differently in recent 
times; in the stable portions the consequences of the oscillations of the 
sea-level in connection with the ice-age will be easily distinguishable 
and unmodified; in the unstable or active portions these oscillations 
must have occurred just as well, but their traces will be distinguishable 
only where they have not been effaced or modified too much by 
the influence of diastrophism, or in other words by the orogenetic 
movements of the land. This is a very favourable circumstance, as 
it enables us to test the theory concerned, in different ways. 
How the Sunda Sea originated. 
In the year 1916 the author briefly pointed out the probability 
of a causal relation between the origin of the above-named remarkable 
shallow seas of quiet submarine topography and constant depth, 
and the pleistocene ice-periods*), and has put forward his view 
that both the Sunda Sea, and the Sahul Bank originated from 
the submersion of a low land by the rise of the sea-level in con- 
sequence of the melting of the great ice-caps of the pleistocene 
ice-age. 
') R. D. M. VERBEEK. Molukken verslag. Geol. verkenningstochten in het 
oostelijke gedeelte van den Ned. O.-I. Archipel. Jaarb. v.h. Mijnwezen XXXVII. 
p. 797, 1908. 
2) G. A. F. MOLENGRAAFF. On recent crustal movements in the island of 
Timor and their bearing on the geological history of the East-Indian Archipelago. 
These Proceedings Vol. XV, 1, p. 282, 1912. ) 
3) G. A. F. MOLENGRAAFF. The coral-reef problem and isostasy. These 
Proceedings Vol. XIX. p. 612, 1916. 
N. Wina Easton followed a similar line of reasoning when discussing the 
origin of the tin-deposits in the Dutch East-Indies. Vide: “Het ontstaan der tinerts- 
beddingen in Indië, Weekblad de Ingenieur, 12 Maart 1919. 
