GEOLOGIC RECONNAISSANCE OF SOUTHWESTERN LUZON. 93 



lake, a descent and detour may be made to the south to reach the 

 remnants of some extinct cones which have level floors. Sulphur fumes 

 and a little steam rise from the cracks in their walls and floors. 



The layers of tuff exposed in the inner wall of the outer crater exhibit 

 bedding and show a banding of colors varying from whites and grays 

 to yellows and reds. The colors are especially vivid on the walls near 

 the points of activity where the hot acid vapors are sublimed on the 

 rocks, forming an efflorescence of iron, aluminium and magnesium sul- 

 phates and chlorides producing variegated white, yellow, red, blue and 

 green effects. Small amounts of native sulphur occur in crevices and 

 cavities, but it is inconspicuous. 



In 1880 Centeno visited Taal Volcano while studying the effects of the severe 

 earthquake of that year, and found that the volcano showed no signs of in- 

 creased activity. From his sketches of the appearance of the volcano and his 

 description we learn that there was at that time one active cone sending up a 

 great quantity of vapor. This active cone seems to correspond with that of 

 his description written in 1882 and is now the crater containing the mud spots. 

 Near the active cone there were some smaller ones which are shown on one of 

 his sketches as giving off thin columns of vapor. 



The yellow lake is described as containing a place near its center where the 

 water boiled up violently and occasionally threw up black mud and sent out 

 waves which agitated the surface of the lake. 



In 1882 Centeno made a study of Taal Volcano and his report is accom- 

 panied by a small hachured map which shows most of che features quite 

 clearly. A model of the volcano inherited from the Inspection de Minas, is in 

 the division of mines. It is probable that the model was based on the map or. 

 was made at about the same time. Studying the model, which is somewhat 

 clearer than the map, but one defect is found which can not be reconciled with 

 the present features of Taal or be accounted for by subsequent changes. The 

 model shows the crater of the red cone as being broken down on the side toward 

 the green lake. As it now exists, it is broken down to the south and drains 

 around its eastern base to the yellow lake. 



Making due allowance for the imperfections of the model and map. 

 certain changes have taken place since Centeno described the volcano. 

 The green lake has extended its area to the southward and contains a 

 point where there is violent boiling. The neck of the peninsula which 

 extended into it from the east has been eroded, leaving the point as a 

 joyramidal rock or island in the lake. A steam vent and a sulphur 

 dioxide gas vent separated by a distance of about 15 meters and evid- 

 ently not connected near the surface have formed at the north base of 

 the red cone. The small inactive cones G and H of Centeno's descrip- 

 tion have been largely obliterated by erosion. The active cone which 

 was described as being about 15 meters high, quite perfect and the point 

 of most activity, giving off great masses of water and vapor, is now 



