PHYSIOGRAPHY OF THE PHILIPPINE ISLANDS: II. 15 



08'; Babuyan Claro, 121° 56'; Camiguin Volcano, 121° 52'; Didicas 

 Volcano, 122° 09', and Cagua Volcano, in northeastern Luzon, 122° 04'. 

 It seems reasonable to infer from the close alignment of the volcanoes 

 of the Babuyanes and Batanes groups and the supposed fault between 

 Sabtan and Ibujos, that the volcanoes mark a fissure in the earth's 

 crust and that their activity may be dependent upon sea water having 

 had access to great depths along the fault. 



COEEELATION. 



There is not enough material at hand just now to enable us to 

 determine the tectonic relations of the Batanes with Formosa and with 

 the Babuyanes and northern Luzon. However, there are certain signifi- 

 cant facts. First, the enormously deep Bashi Channel seems to trend 

 in a northeasterly direction. If so, it may represent a geosyncline or 

 trough, parallel to the tectonic lines shown by Von Eichthofen along 

 the southeast coasts of China and Cochin-China and to the northwest 

 coasts of Borneo and Palawan. This deep channel prologed, would 

 enter the 4,000-|-meter "deep"' of the northwest coast of Luzon and 

 follow the 2,000-|-meter "deep" to the southeast of the Eiukiu Islands, 

 hence, by inference, making the Philippines and Japan (including For- 

 mosa) separate geologic provinces. Professor Koto ^^ sums up the 

 present geological knowledge of Botel Tobago (Koto) as follows: 



"Fringing reefs are said to skirt the shore, some portion attaining double man's 

 height above the water's edge, indicative of a recent negative shift of the relative 

 levels. It seems to me probable that they are not the reefs of Neocene time, 

 which usually attain a considerable height of more than 200 meters as in the Apes 

 Hill of Takao, but those of a comparatively recent date, possibly representing a 

 diluvial formation. The plateau-like elevation, which faces the sea in cliffs, 

 seems in parts at least in the northeast point to consist of volcanic agglomerate. 

 A greater part of the interior seems to be built of volcanic rocks with a gabbro- 

 like plutonic mass as the foundation of the island exposed at the west coast, but 

 their mutual relations and area of distribution are quite unknown to me." 



Professor Koto also gives petrographic descriptions of feldspar basalts, 

 hornblende andesites, apoandesites, gabbro and serpentine from Botel 

 Tobago. 



Thus, the existence of a volcanic island in longitude 121° 30', although 

 across the Bashi Channel from the Batanes and the great Taito furrow 

 running IST. 20° E. from the southern point of the island,^'' together 

 with the Taito Eange just to the east of it, may be more than mere 

 coincidences. 



The chain of volcanoes is certainly significant in regard to the relation 

 of the Batanes Islands to the Babuyanes and northern Luzon, as is also the 

 separation of the limestone islands of the groups from 'the volcanic ones. 



•V. of the Coll. of Sci. Tokyo (1900), 13, 46. 

 >=Hobbs, W. H.: Am. Geol. (1904), 24, 374. 



