NORTHWESTERN PANGASINAN. Oy 
Relief.—The relief of the area is quite moderate, seldom reach- 
ing a height over 130 meters. The region, within comparatively 
recent times, has been gently uplifted above sea-level and ero- 
sion has subsequently cut out the various topographical forms. 
This uplift, as discussed later, began in the Pliocene age and pos- 
sibly is even now taking place. The erosion generally is im- 
mature, and the majority of the rivers are incised in narrow 
sharp valleys which broaden into flood-plains just before enter- 
ing the sea. A central sea-level river flood-plain occurs sur- 
rounding the municipality of Alaminos, and is flanked by hills 
to the east, south, and west. 
The eastern range of hills extends from the southeast corner 
of the area northward to the sea and marks the termination of 
the Zambales Mountains. These mountains extend in a nearly 
unbroken line from the entrance of Manila Bay northward to the 
area. 
In the southeast corner of the area, Mount San Isidro, elevation 
890 meters, forms a prominent feature of the landscape. The 
shape of this mountain is somewhat conical with two conical 
points which apparently represent stocks of volcanic vents. 
From Mount San Isidro the hills decrease in altitude northward 
to the China Sea. This decrease is broken 5 kilometers from 
San Isidro by the central summit known as Verde Mountain, 
which rises to an elevation of 427 meters. 
The southern hills spread out from the eastern hills and rep- 
resent an uplifted formation now being deeply incised by river 
action. They embrace the headwaters of the Alaminos and 
Balincaguin Rivers, and are characterized by narrow valleys and 
precipitous slopes. The rivers are rapidly cutting canons into 
the formations, and the side hills have not yet had time to round 
over into the more mature forms. Cliffs and buttes are fre- 
quently seen. 
It is quite probable that the Balincaguin River began its erod- 
ing action in the Zambales Mountains before the more northern 
portion of the area emerged from the sea; and as the region rose, 
the river has continuously lengthened its course northwestward. 
The western hills extend from the northwest corner of the 
area into the southern hills, and similarly represent, an uplifted 
formation incised by river action. In form these hills are typ- 
ically plateau-like, and their even sky-line is a marked feature 
of the topography. 
Just west of Bani, the line between this plateau and the Ala- 
minos flood plain is marked by a long scarp. This is in part 
due to river action, yet it is quite probable that part of the ero- 
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