86 ADAMS. 



are exposed in the sea cliffs of the table-land at Locoloco Point and at 

 Malabrigo Point. It is probable that this formation, which also contains 

 some marls, is similar to the raised coral reefs in Santiago Peninsula, 

 described subsequently in this report. The formation is perhaps the 

 equivalent of the tuffs lying to the north of the Loboo Mountains and 

 found to a limited extent within their area. The occurrence of the 

 tuff formation in the Loboo Mountains has been noted by Smith and the 

 writer has been assured by travelers that it borders the region to the 

 north and that the occasional outliers are found within the mountainous 

 district. 



Geologic history. — The occurrence of diorites in the Loboo Mountains 

 and the existence of Tertiary sedimentaries and andesites indicate that 

 the geologic history is complex and somewhat similar to that of the 

 eastern cordillera. The relations of this mountainous area to the struc- 

 ture in other parts of Luzon is discordant. Perhaps when the history 

 of Mindoro and Verde Island, which intervenes, are well known the 

 Loboo Mountains may be found to be related to them. At present, the 

 region is too little studied to warrant very definite statements regard- 

 ing it, 



SOUTHWESTERN VOLCANIC REGION. 



Extinct volcanoes. — There are three peaks in this region which are 

 usually considered to be extinct volcanoes, viz, Banahao, Cristobal and 

 Maquiling. Banahao and Cristobal probably should be referred to the 

 same volcanic center, Cristobal being a subordinate cone. 



Banahao as seen from the southwest is quite symmetrical. It contains 

 a large crater reported to be 210 meters deep. To the northeast there is 

 a sharp subordinate peak called Banahao de Lucban, or Banahillo. Cris- 

 tobal lies to the northwest. It has a crater in which there are three 

 small lakes. To the southwest there is Mount Masalacot and some hills 

 which belong to the same area. There is no evidence of recent volcanic 

 activity of Cristobal and eruptions attributed to Banahao should prob- 

 ably be explained as avalanches of mud and stones produced by the break- 

 ing of natural dams formed at the outlet of the crater, by landslides 

 and debris falling from the cliffs. Jagor in a footnote states that it is 

 recorded in the Estado Geogrdfico, Manila, 1865, that Banahao has been 

 extinct since 1730, in which year it had its last eruption, breaking out 

 on the southern part and vomiting torrents of water, hot lava, and 

 stones of monstruous size, the signs of which may be seen until the 

 present time at the town of Sariaya. This supposed eruption was also 

 noted by Becker in his paper. In January, 1909, the newspapers stated 



