74 PRATT. 



portion, blew approximatelT X. 55 " E. and that the force of the eruption 

 was directed to the west or slightly northwest.^* 



The conc^enrration of the force of the Toleanic action in a certain 

 direction may be attributed most reasonably to the contour of the crater 

 rim which (Plate III) is lowest and most distant from the actiye 

 part of the crater in its western and northwestern portion. However, it 

 will be noted that the southwest side of the rim is comparatively high 

 and close to the active crater, yet destruction was complete and extensive 

 to tiie southwest. A suggested explanation of the greater devastation to 

 one side of the crater, lies in the assumption that the throat of the vol- 

 cano is not vertical but dips to the east, thus directing its ejeeta to the 

 west. Such an assumption is unnecessary and is probably not warranted 

 by the evidence which appears to support it. 



EAETH FISSURES. 



Descripiioii and trend. — The system of fisstires (See Plate I) which 

 formed during this eruption is significant of the relation of Taal Vol- 

 cano to the general structure of the region. This subject has been one 

 of c-onsiderable interest to geologists who have studied this area, Cen- 

 teno ^~ plac-ed Taal on an approximately north and south line with 

 Mount Arayat in the central valley of Ltizon north of Manila, 

 Adams ^* thiaks it probable that Mount Arayat is on the same struc- 

 tural line as Taal and argues that the general trend of structure in 

 southwestern Ltizon is to the northwest. However, he suggests the 

 possibility of a line through Balayan Bay. Taal Tolc-ano. and Laguna 

 de Bay. and sees a possible elevated fault-block in the high ridge north 

 of Lake Bombon and west of sach a line. 



The trend of the recent fissuring indicates a line of weakness passing 

 through Taal Volcano and bearing about X. 30° E. This trend extended 

 beyond the limits of the system and rtms closely parallel to the east 

 coast of Luzon and the length of Palawan, passing through Laguna de 

 Bay and Balayan Bay. (See index map, Plate 11.) The earthquakes 

 were strongest in Taal and Talisay, along this line. The alignment of 

 craters on Volcano Island conforms well with such a trend as do also 



^At Subig, sonth-west of the crater -where the mud fell 10 centimeters deep, 

 a considerable portion of the town was swept bv the -vrater wave resulting from 

 the explosion. This area was left qiiite clean of mud, -while up to its limits 

 the general depth prevailed. At TaUsav and Bafiadero,. northeast of the crater, 

 and slightly more distant, the low ground washed bv the water wave showed the 

 same depth of mud as the adjacent upland. Apparently the whole fall of mud 

 due entirely to the explosion at Subig had oecitrred before the water wave finally 

 receded and it was carried away by it, while at Talisay and Banadero, whither 

 the mud was c-arried by the -wind, the fall occurred after the ware had receded, 

 and covered the area washed by it. 



"Estudio Geologic© del volcan Taal, Madrid, Tello (18S-5i. 



"Tfci* Journah Sec. A (1910), 5, 101. 



