GEOLOGIC RECONNAISSANCE OF SOUTHWESTERN LUZON. 91 



probably being cinder cones in describing the evidences of activity around 

 the base of Maquiling. 



Crater lakes. — The crater lakes probably owe their origin to phenomena 

 closely allied to those which produced the cinder cones. The rims of 

 the lakes usually rise a little above the surrounding country and suggest 

 that they are the remnants of cones which have collapsed and subsided. 

 In the country around San Pablo there are a number of crater lakes 

 which are readily accessible, and San Pablo is coming to be known as 

 the center for tourists visiting the crater-lake country. The first descrip- 

 tion of these lakes is by Jagor, who visited several situated near San 

 Pablo. He described them as having circular embankments with very 

 gentle outer slopes formed of lapilli. The interior Avails of the rim are 

 usually very steep. Most of the lakes are drained through clefts in the 

 crater border which have been formed by erosion. The streams flowing 

 from them, like most of the streams of the volcanic region, have steep 

 banks and narrow channels. The lake most easily accessible is the one 

 situated just north of the town of San Pablo and it may be reached by 

 a few minutes' walk to the end of one of the streets. Two lakes occur 

 on the public highway east of San Pablo. They are near the road and 

 can easily be visited by travelers by stopping a few minutes and walking 

 through the groves of coconut palms. 



These lakes, besides being of interest because of their origin, are made 

 picturesque by the vegetation which grows on their borders. Some of 

 them afford a good supply of fish to the neighboring inhabitants. 

 However, others are partially drained and the abandoned lake beds are 

 planted with coconut trees. Not all of the crater lakes which have been 

 indicated on the reconnaissance map were visited, but information 

 concerning them has been obtained through inquiry. . It is interesting 

 to note that a lake which occupies the remnants of a small crater is 

 situated near ISTasugbu. The distribution of the crater lakes and cinder 

 cones shows volcanic activity to have been extended over a large part 

 of the southeast district and it is probable , that the deposition of the 

 tuff formation has obscured many of the early vents and that others 

 have been completely eroded. 



The active Volcano Tool. — Taal Volcano is situated on an island in 

 Taal or Bombon Lake. The island, on which are found a number of 

 extinct cinder cones and the active crater, has been built near the center 

 of the lake by late volcanic activity (Plate III). The main crater which 

 is situated near the center is usually referred to as Taal Volcano. It 

 is approximately circular in form. The southwestern border of the 

 crater rim rises to an elevation of 320 meters, which is the highest point 

 on the island. The lowest points on the rim are about 130 to 150 meters 



