The National tribune., 1902-08-21
PHILIPPINE EARTHQUAKES AND VOLCANOES.
Evidence Of Past Volcanic Activity Presented by Extinct Craters
Records of Seismic Disturbances.
By CAPT. HYLAND c. KIRK



Altogether II active volcanoes are
enumerated as existing in the Philippines
and some II which are pronounced ex
tinct; but neither of these numbers cal
be regarded as definite. Scme of these
active volcanoes, Bulusan and Bacon, fol
example, show but the merest trace OF
yapor at their submits, and may never
erupt again; while some long inactive
may again show signs of life, if they dc
not indulge in violent eruptions. Thus
DIR. Kemper claimed recently to have
seen a cloud of smoke issuing from the
crater of Caua, located at the northeast
point of LuzOn and long reported as ex-
tinct. Besides, if we count all the ele-
vations with cavities, or with what have
evidently been craters at some time Ill
their vicinity, we shall have very large
list of inactive volcanoes.
Mount Madia-as, the highest peak on
the Island of Panay, which rises I,l52
feet above sea-level, has undoubtedly an
extinct crater in its top. This is shown
by the numerous streams which pour
'from aloft'' down its sides OF three
photos which l secured none was taken
under sufficiently favorable circum-
stances to show this. l was informed at
Colasi that Madia-as had never been sue
cessfully ascended, but that one or two
fatalities had resulted from such
attempts. Another fact pointing to
its volcanic character is that its peak is
formed of basaltic rock, hard and firm
as glass, of intense black color. Similar
ly Mount Nasog, or Cresta de Gallo,
south coast of Panay, has crater-like
depression in its side and is composed
largely of andesite and diorite; volcanic
rocks abound, in fact, throughout the
Antique Range.
EXTINCT VOLCANOES.
In the case of many old craters the
evidences of their former cruptive char
acter have been in great degree obliterat-
ed. The crater of Bana jaO, or MayJayJay,
south of Laguna de Bay, LuZon, is now
completely covered with trees and vege-
tation: yet in 1730 it destroyed the town
of Sariaya, and for a considerable period
its crater, some three miles in circumfer-
ence, formed a lake.
Banajao. the BOtocan River leaps 14O
meters (460 feet from volcanic rock
to the gorge below. The crater of Ma
quilting. northwest of Banajao. and near
the town OF Los BanOs. though the walls
are abrupt and steep, is thickly wooded.
Evidence of crater-obliteration and sub
sidence of volcanic action is shown also
in the geysers and numerous hot springs
of which some 200 have been located in
the islands. The waters of about three
fourths of these have been analyzed and
some pronounced of great medicinal val
ne. Another evidence is shown in crater
lakes which exist at comparatively low
levels.
A volcanic eruption is reported to have
occurred at Buhayan, Mindanao, in 164O.
so violent as to be heard at Manila. 400
miles away; as q sequence OF which the
entire mountain is said to have disap-
peared and lake formed in its place. If
this account is correct. the reported erup-
ton in that year of Mecaturin, previously
referred to. may be mistake, as Maca-
turin is located ih a section known for
merly as Buhayan.
Lake Mainit, or SapOngan. in the Dis
frict of Surigao. which extends eight
miles north and south and about six
miles east and west, is undoubtedly the
crater Of an extinct volcano. Its sides
are steep, extending abruptly downward
60 feet, and it is 1,200 feet deep in the
middle; while the surrounding mountain
slopes abound in hot springs.
SEISMIC DISTURBANCES.
With all this data relative to volcanoes,
as earthquakes occur with frequency,
there is no part of the world probably
duoTulHS UtlteT IiCllltleS LOT Tie Stuug
of seismic and volcanic phenomena than
this archipelago. The Spanish scientists
located 10 seismic foci in the isiands-fve
in Luzon, and five in Mindanao. In this
arrangement the foci are supposed to he
determined by generalizing the direction
and intensity of wave-mOvements in diff
ferent earthquakes; earthquake and vol
canlc centers, however, are seen to be in
Fretty close agreement. The Spanish also
divided the islands, apparently as a mat
ter of convenience, into three seismic
zones separated by parallel lines; South
e-n. including Mindanao and all territory
south of the 10th parallel; Central, in
cluding the Viscayan Islinds and LuZon
t. nearly the 18th parallel Of latitude;
and The Northern, comprising the remain
de- CT Luzon, the Babuyanes and BataBes
Islands, north. They enumerated three
classes of shocks: Vertical movements
Grepidatcrio); horizontal movements ton
dulatorio); and rotary movements (rota-
ciobt.
The most dangerous on record are of
the first class; i'll violent disturbances,
however, the second are usually COM
bined with the first. The rotary move
ments seldom occur. and of a dozen re-
corded instances, but one or two are put
down as strong, and none as violent. In
general, violent earthquakes are styled
terremotos, and ordinary shocks, tenn
plores.
As illustrating the frequency OF earth
quakes. Padre Urios, S. j., reports that
at Surigao in January, 1889, there were
100 shocks in q days. The great ma
jority of shocks recorded are not noticed
by the ordinary observer. In my own
experience of nearly two years in the isl
ands $500 and 190D, / recall but three
definite shocks-two in Manila, and one
Et IloilO; while a score or more were re-
corded by instruments.
If we assume the current theory that the
ultimate cause Of both earthquakes and
volcanic eruptions is the secular cooling
Of the earth and adjustments of pressures
on its surface where faults occur in the
crust. we shall find some Interesting ex-
emples in the seismic records of the Phil
ippines. Among these, illustrations that
earthquakes are sometimes due apparent
1y TO vacua created by volcanoes, as al
ready referred to in the eruption of Ma
caturin. 1871, and of Conloan, 1894, and
that volcanic eruptions often follow the
agitations of earthquakes and seem to re-
lieve them, as in eruptions already mcn-
TONED of Taal, 1910; Bacon, 1910; May
on, 1853 and 1855, and Bulusan, 1880.
EARLIEST RECORDED EARTHQUAKES.
The earliest recorded earthquake oc-
CURED in Luzon in 1899. 1t is reported
as having been very violent and destruc-
tive. One mentioned by Aduarte as oc-
curing on st. Andrews Day. 1910, af-
fected the whole Island of Luzon from
Manila north. He says: 1T caused
great destruction over the whole area