GEOLOGIC RECONNAISSANCE OF SOUTHWESTERN LUZON. 95 



new island the larger part of which subsided, leaving remnants which are known 

 as Bubuing and Napayong Islands. 



In 1749 a violent eruption began on August 6 and continued about three 

 weeks. Some settlements near the shores of the lake suffered damage from the 

 seismic disturbances and falling ashes. There were no flows of lava, but in- 

 candescent stones were thrown out. Eruptions took place in the lake to the 

 north and east of the island. 



In 1754 the greatest historical eruption took place, lasting from May until 

 December. The towns of Sala, Lipa, Tanauan and Taal, then on the border 

 of the lake, were destroyed, and Balayan, Bauan, Batangas, Rosario, Santo 

 Tomas and San Pablo suffered great disasters. The rain of scoria and ashes 

 extended over a much larger area. The surface of the lake was covered with 

 patches of floating pumice and ashes. Incandescent stones were thrown out 

 and fell into the lake. There Avere, however, no lava flows. Heavy rains 

 descended and the barrio of Balili near Sala was covered with a shower of 

 mud. 



In 1808 there were eruptions of slight intensity which began in February 

 and continued until the end of April, but no damage was done to the inhab- 

 itants who, after the disaster of 1749, nad returned to settle on the margin 

 or the lake. 



The eruption of 1904 which has already been described was unimportant. 

 It is the first one of which photographs have been published. 



Agglomerates of the southwestern region. — There are extensive beds 

 of agglomerates found in the tuff formation, as has already been noted. 

 They are seen principally around the northern base of Banahao where 

 the streams flow in deep gorges. In other localities angular fragments 

 of andesite and basalt are found included in the tuff but not forming 

 true agglomerate beds. 



To the west of Balayan there is a line of sharp peaks which present 

 an escarpment on the eastern side. The exposures which were seen in 

 sheer faces in this escarpment appear like conglomerates. Masses which 

 had fallen from the cliffs were examined and although the material was 

 badly weathered it seemed that the formation should be classed as an 

 agglomerate. Its occurrence is noted in the accompanying geologic map. 

 It is probable that a fault passes along the eastern base of this line of 

 peaks. The origin and extent of the agglomerates and the position of 

 the fault line could not be determined. 



Tuff formation. — The area of the tuff formation, as shown in the 

 accompanying geologic map, includes localities which have been described 

 by previous writers as containing principally water-laid tuffs. The 

 higher areas probably include subaerial formations and near Taal Volcano 

 there are remnants of recent showers of volcanic ash. Von Drasche 

 indicates in his map (Plate I) a large portion of the tuff deposits. 



