20, 3 Schenck: Physiography and Geology of Samar 237 
Attention should be called to the rough topography in the 
limestone districts, such ag at Matuguinao, where there are great 
_ caverns, sinks, and subterranean streams. The caving of these 
sinks results in the formation of coves and, later, valleys. Men- 
tion has been made elsewhere of islands that have been formed 
from blocks of limestone cut off from the parent mags. 
When one considers the causes for the nature of the topogra- 
phy, one sees that the stage of maturity has resulted from 
variation in the hardness of the rocks, differential crustal move- 
ments, and erosion due to excessive rainfall. 
OUTCROPS AND TOPOGRAPHY 
Along the west coast of Samar, principally south of Calbayog, 
the shale hills with their inland dip and steep seaward escarp- 
ment furnish abundant outcrops, and at low tide harder beds 
are exposed. The topography here is that of shale hills result- 
ing from minor folding, minor and major faulting, and tropical 
erosion. | 
Good outcrops in the beds of creeks can be seen on the north 
coast, where durable sandstones and a well-cemented conglom- 
erate, especially near the Catarman Agricultural School, give 
_ & prominent, but not high, coastal ridge. The northwest corner 
of the island is composed in part of hills of basalt now in ero- 
sional youth. 
On the south coast the best exposures are along the seashore. 
They consist of massive limestone masses, which are being un- 
dercut by wave action. Near the sitio of Hilaba, municipality 
of Basey, a series of hat-shaped islands has resulted from this 
undercutting. Near the town of Basey, opposite Tacloban, Leyte, 
is a prominent shale and sandstone hill, overlain by what may 
be a river conglomerate, 
On the eastern side of the island the low hills lying inland 
from the coastal plain are chiefly composed of soft sandstone, 
marl, and a lignitic clay, which have been exposed by the cutting 
action of the streams. On the left (north) bank of Malinao 
(Tubig) River, opposite the barrio of Taft, is a faceted spur of 
Massive, bluish marl. There is a narrow coastal plain in this 
region, and coral reefs occur offshore. 
The outcrops in the interior of Samar seen by our party were 
found chiefly in creek beds, and they consisted of flat, sandy 
Shale (marl), clay, limestone, some andesite and basalt, and on 
Ulot River east of Loquilocan a hard plagioclase porphyry. As 
