FERGUSON. 



The Island of Sabtan is the southernmost of the Batanes Group. It 

 is about 10 kilometers long by 4 broad and contains five villages, San 

 Vicente, Santo Tomas and Santa Eosa on the east coast, Santa Ines and 

 San Luis on the western side. From Point Natao southward on the 

 east coast to within half a mile of Santa Eosa, there is no marked relief 

 along the shore, with the exception of some high bluffs of volcanic agglom- 

 erate just south of San Vicente. Coral reefs extend over a large part 

 of the coast, although their development here is not as extensive as on 

 the west coast. South of Santo Tomas there is a long, fiat stretch near 

 the shore and here sand dunes reaching to a height of about 100 feet have 

 dammed back the waters from the interior, fonning a line of small ponds. 



The land from the eastern shore rises toward the center of the island 

 in a rather irregular series of marine terraces. The materials forming 

 these terraces are stratified pebbles and sand, for the most part entirely 

 unconsolidated, together with limestone, the latter both limestone con- 

 glomerate and coral limestone. These terraces when viewed from the 

 neighboring island, Batan, seem to be beautifidly regular, but on closer 

 examination they are seen to be absolutely without continuity, probably 

 due to the fact that where the protecting capping of limestone is absent, 

 the terrace of pebbles and sand is soon worn away. The highest ledge 

 of limestone occurs at an elevation of about 180 meters. It is a quarter 

 of a mile inland and contains poorly preserved Orbitoides. Beyond the 

 last terrace, the country is very deeply dissected and consists of irregular, 

 sharp ridges of volcanic agglomerate, generally much decomposed. 



A belt of rolling upland between a half mile and a mile wide extends 

 diagonally across the island from Santa Eosa to Santa Ines. This has 

 an average elevation of about 300 meters; it is bounded on the east by a 

 sharp and very irregular escarpment of volcanic agglomerate. The valleys 

 in this upland are broad and the small streams seem to be at grade, the 

 topograi^hy being best described as "gently rolling," in marked contrast 

 to the sharp feature of the irregular ridges below, in general it is a 

 region of physiographic "old age." This upland rises gradually to the 

 westward, the pass a half mile northeast of San Luis having an elevation 

 of 400 meters, and it ends in a sharp line of cliffs broken only by occasional 

 steep canyons. These cliffs extend along the whole west coast of the 

 island, being lower (200 meters) towards Natao Point. The material 

 is almost entirely volcanic agglomerate, with occasional beds of stratified 

 sandstone and conglomerate which consist entirely of volcanic material. 

 This rock where it occurs is much faulted, the faults being of small throw, 

 generally less than 10 feet, and also somewhat distorted, showing small 

 dips to the west and northwest. Of course, the folding and faulting are 

 not confined to those parts of the agglomerate formation in which the 



