520 W. D. SMITH GEOLOGIC INFLUENCES IN THE PHILIPPINES 



agencies accelerated. This acceleration seems to depend chiefly on the 

 following factors : 



1. Excessive rainfall. 



2. High mean annual temperature. 



3. G-reat relief due to high declivity of streams. 



4. Increased amount of chlorine, due in part to salt blown in from the 

 sea. 



5. Excess of vegetable acids. 



6. Seismic disturbances. 



In contrast to these degrading agencies we have the almost as impor- 

 tant volcanic and diastrophic effects which tend^ in part at least, to build 

 up. The former is too patent to dwell on further than to say that a large 

 part of the surface material is of volcanic origin in many parts of the 

 islands. The increase of the land quantities by diastrophic movements 

 is not so clearly seen, nor is it probable that it amounts to very much in 

 any ordinarily reckoned period of time. The apparent elevation on the 

 west coast possibly may be compensated by the very evident subsidence 

 which has taken place on the east coast. 



The salient features in the physiography of the Philippine Archipelago 

 are: 



1. The irregular configuration of the archipelago and the great mileage 

 of the coastline. 



2. Large development of mountains and the arcuate arrangement of 

 most of them. 



3. ■ The proximity of the mountains to the sea. 



4. Narrow and interrupted coastal plains due to the foregoing. 



5. Five principal intermontane plains. 



6. River systems which principally flow north. 



7. Varieties of lakes and their origins. 



Irrj<]gular Configuration of the Archipelago 



The general outline of the Philippine Archipelago is suggestive of a 

 giant sloth with Luzon for the head and shoulders, the Visayan Islands 

 for the middle portion of the body, Mindanao for the pelvis, Palawan- 

 Cuyo for the fore legs, and the Sulu group for the hind legs. The body 

 of the animal appears as if it were inclined forward. But this analogy 

 must not be carried too far, since the resemblance vanishes when we begin 

 to look for the details of the skeleton. 



The bulk of the land-mass lies east of the main portion of Luzon, the 

 axis of that portion extending northwest and southeast at an angle not 



