24 FERGUSON. 



of the streams and the cutting of steep canons. The locus of volcanic 

 activity is now shifted from the region of Sabtan to a line along the 

 one hundred and twentj'-second meridian. 



Faulting between Ibujos and Sabtan cut off part of the old upland, 

 leaving a well-marked fault scarj) along the west coast of Sabtan and 

 growth of coral and later elevation brought a limestone mass, of which 

 the islands of Isbayat, Ibujos and Desquey are remnants, to the surface. 

 It seems probable that this fault extends southward through the Babu- 

 yanes group and it is possible that the Cagayan valley may represent its 

 continuation in Luzon. The large number of earthquakes recorded in the 

 Batanes indicate that movement along this fault is still going on. 



The recent history of the Batanes Islands is mainly one of lessening 

 of the area. The land appears to be stationary and nothing is gained 

 through uplift. The upbuilding force of vulcanism has ceased, leaving 

 the growth of coral reefs the only force acting in opposition to the erosive 

 action of the waves, streams and tides. The work of man in deforesting 

 the ridges is assisting in the wearing down of the land. 



