GEOLOGIC RECONNAISSANCE OF SOUTHWESTERN LUZON. 63 



hot springs. At Los Baiios these are utilized by the military sanitarium 

 and private institutions. There are thus three mountains, Banahao, 

 San Cristobal, and Maquiling, retaining evidence of former volcanic 

 activity. 



To the east of Maquiling and to the northwest of San Cristobal there 

 is an important group of lower mountains lying between Calauan and 

 Nagcarlang. 



The next important mountain is Malarayat-Sosoneambing, having an 

 elevation of 1,005 meters. It is a rough, ridge-like mass extending from 

 north to south, and lying to the south of Maquiling. Mount Macolod 

 on the southeast shore of Taal Lake has an elevation of 958 meters. 

 A striking feature of this mountain as seen from the north or south is a 

 high precipice facing Lake Taal. 



Mount Gonzales, to the north of Lake Taal, with an elevation of 749 

 meters, has rugged slopes and spurs to the east and northeast. To the 

 west it blends with a high ridge of volcanic tuff which runs in a curve to 

 the southwest, joining Mount Batulao. This mountain has an elevation 

 of 807 meters and its slopes to the west and south form an area of broken 

 country. A group of peaks to the northwest of Mount Batulao forms a 

 small mountain mass, the highest point of which is Mount Carilao, eleva- 

 tion 636 meters. Looking south and a little west from Manila, Mount 

 Gonzales is visible, the ridge running from it to Batulao and the tuff 

 plains sloping toward Manila Bay. Mount Caralao appears on the 

 western limit of this sloping plain in the gap between Mount Batulao 

 and the Pico de Loro Mountains. 



This concludes the catalogue of the principal mountains which are 

 here classified as within the tuff plains. They are neo-volcanic and taken 

 as a whole exhibit no well-defined trend. The watershed between the 

 streams which flow northward and those which flow southward in the 

 tuff plains passes through Banahao, Cristobal, Gonzales, and Batulao. 

 The divide does not pass through mountain peaks between Cristobal and 

 Gonzales, but takes an irregular course through the plains. On the 

 south the streams flow into Balayan, Batangas, or Tayabas Bays. The 

 division into these three groups is determined by the mountainous 

 peninsular areas separating the bays. The nortward-flowing streams 

 enter Manila Bay or Bay Lake. The division into these two groups is 

 marked by a ridge presenting an escarpment to the east and extending 

 from Mount Gonzales northward to where it is cut by the Pasig Biver 

 which drains Bay Lake, and beyond this continuing to the east of the 

 Mariquina Biver until it approaches the foothills of the eastern cordillera. 

 The reasons for these various divisions of the drainage will be made 

 more clear when the deposition of the tuff, the elevation of the region 

 and the origin of Bay Lake are discussed. 



The remaining mountains of this region are in peninsular areas. The 



