CHANGES OF LEVEL IN THE PHILIPPINES 519 



observer. It is probably because of the great extent of the Philippines 

 and the complications of their history that neither Becker nor Smith is 

 very explicit regarding the physiographic aspects of the development of 

 the archipelago. For example, Smith states: "There undoubtedly has 

 been a general subsidence at times of the whole archipelago/^ and "a 

 corresponding and a very general elevation" (521) ; but it is not clear 

 from the context what form the islands had when these movements took 

 place, and without an understanding of that physiographic element the 

 progress of events is not clear. 



The best inferences that I can make lead me to think that oscillations 

 of large value, varying from place to place, have been added to the simple 

 scheme of a Miocene submergence and a later emergence of the whole 

 group; for Pliocene, Pleistocene, and Kecent time are long enough for 

 many changes of level, as well as for much erosion and deposition during 

 such changes. The sharp irregularities of the shorelines of many islands 

 can hardly be explained by a simple three-phase scheme of ( 1 ) Eocene de- 

 formation and uplift, with the addition of erosion that is implied but not 

 physiographically expressed; (3) Miocene depression, with the deposition 

 of reef limestones as well as of sediments, which should be abundant in 

 a mountainous and rainy archipelago, and which should cover over and 

 soften the submerged surfaces of subaerial erosion, but of which little is 

 said; and (3) post-Miocene elevation, with reef grov^th during pauses. 

 It therefore seems legitimate to expand this simple scheme by the addi- 

 tion of later and more or less recent oscillations, and in connection with 

 the coral-reef problem to give special emphasis to the recent movements 

 of depression that are attested by the submerged platforms, the minutely 

 irregular shorelines, and the narrow fringing reefs of certain islands. 



This conclusion is fully borne out by studies of other archipelagoes, 

 where reef limestones occur at altitudes of 1,000 or 2,000 feet and where 

 Pliocene and Pleistocene deposits are frequently deformed; and from all 

 this it must be inferred that upheavals as well as subsidences of various 

 measures have been much stronger and more frequent in the Australasian 

 archipelago than in the central Pacific, east of Fiji and Tonga, where 

 elevated reefs are comparatively low and rare. The archipelagoes thus 

 appear to be the seat of active and diverse movements of subsidence and 

 upheaval, while the central Pacific is characterized by relatively slow sub- 

 sidence. Return will be made to this subject on a later page. 



THE PHILIPPINES AND THE QLACIAL-CONTROL THEORY 



The discontinuous reefs of the Philippines ,not only support the expla- 

 nation given by Darwin for fringing reefs of a new generation, but also 



XXXIX — Bull. Geol. Soc. Am., Vol. 29, 1917 



