522 W. D. SMITH GEOLOGIC INFLUENCES IN THE PHILIPPINES 



Planet, which located the deepest kno^vIl part of the Pacific Ocean as 

 being 53 miles northeast of the Mindanao coast, in 1910. This depth 

 was reported as being 9,780 meters. 



DEVELOrMP:NT AND ARRANGEMt'^NT OF MOUNTAINS 



The mountains of the Philippines lie generally in ranges that parallel 

 the coastlines and which lie in close proximity to them. They are of two 

 principal types : Those due to uplift with folding and erosion, and others 

 due to vulcanism and more or less eroded. 



The highest peak in the islands is that of Mount Apo, in Mindanao, of 

 volcanic origin, which is 9,610 feet in height. 



The most prominent chain of all is in Luzon — the Cordillera Central — 

 which stretches from the northern boundary of the central plain to the 

 Pacific Ocean, forming the backbone of this island. It is a composite of 

 two, and in some places of three, parallel ranges, each of which averages 

 about 6,000 feet in elevation. The highest peaks of this range, beginning 

 from the south, are: Mount Santo Tomas, 7,240 feet; Mount Pulog, 

 9,400 feet — the highest peak on Luzon; Mount Data, 7,360 feet, and 

 Mount Amuyao, 8,857 feet. The range is largely intrusive and extrusive 

 andesite, with sediments exposed high up on its flanks. 



The Cordillera Central, as well as the two coast ranges of Luzon, may 

 be said to be in that stage of physiographic development known as "topo- 

 graphic youth'^ or, in places, '^^early maturity." Hence the cross-sections 

 of the stream valleys is "V"-shaped, which, however, may be modified to 

 "U"-shape by the excessive talus accumulation from volcanic agglomerate 

 cliffs above. Outcrops and falls are common along the main channels 

 and there rarely are any great accumulations of wash in the stream chan- 

 nels, owing to the terrific scouring of the mountain floods. 



In several localities, but especially in and around Baguio — the site of 

 the summer capital of the islands — there is some plateau development. 

 The topography of the Baguio plateau is strikingly like that of a glaciated 

 region. The hills are rounded and veneered, usually with volcanic tuff, 

 with scattered volcanic blocks, which at a distance resemble erratics, 

 ponded drainage, etcetera. The writer at first was strongly of the opinion 

 that he had found evidence beyond dispute that there had been glaciation 

 in the highlands of Luzon. When, in the gullies, he came on deposits 

 with angular blocks in hard clay, duplicating the general appearance of 

 glacial till, he was almost certain of it. Fortunately he was persuaded 

 by a fellow-worker, who had been in the tropics for a longer period- — A. J. 

 Eveland, formerly of the Philippine Mining Bureau — to ponder further 



