The Hawaiian gazette. [volume] (Honolulu [Oahu, Hawaii]) 1865-1918, 1900-08-10
GEOLOGY OF
OAHU ISLAND
Review of HitchCoCk's
Pamphlet.
NOTES BY SEREN0 BISHOP
An Interesting Treatise on the
Formation Of the Land
We Live in.


titled the Geology of Oahu" which Is
a report of geological observations ana
conclusions respecting the Island OF
Oahu, made by Professor Charles H.
Hitchcock, LID, including three
pages of Notes on the Tertiary Geol-
ogy of oahu" by w. H. Dali. Although
the geology of this Island has been ex-
tensiyely discussed before, by Prof j.
ID. Dana, by Prof w. II. Brigham, by
w. Lowthian Green by Capt. c. e.
Dutton. by Messrs. w. d. Alexander.
A. e. Lyons and Walter Maxwell, yet
DR.. Hitchcocks work constitutes val
liable manual of the subject, with I'M
portant additions to previous knowl-
edge, says DR.. Bishop. Besides obser-
vations made during two previous VS.
it's, DR.. Hitchcock in 1SSS-S9, carefully
inspected a great number of locations,
especially along the line of the Oahu
railway, the Nuuanu Pail, and the
series of secondary craters along the
coast.
A leading place is given to the origi-
nal separation of Oahu into two islands
now represented by the kaala range,
and the Kooiau range. The former is
much older than the other, as evidence
ed in many ways. Volcanic activity had
perhaps ceased on Kaala before the
Koolau mountain had been built up by
it's eruptions much above the surface
of the ocean. DR.. Hitchcock develops
the fact pointed out by Dana, that
enormous outfows of lava from the
northern half of Koolau mountain
flooded and built up the broad plateau
between Eva and Waialua. The al
ready deeply eroded canyons of the ka-
ala range were invaded by this plateau
of lava, and their lower parts buried
therein. Similar elevated plains nave
been built up by like means in Waimea,
between Maunakea and kohala noun
tain, also between Maunakea and Maui
naloa One may conjecture that before
the deep subsistence of Oahu the Waia-
lua plateau was as high as Waimea, al
though now LOO feet lower.
DR.. Hitchcock adopts the now gen
orally accepted conclusion that pr
Dana was in error in believing the
great Kaneohe amphitheater to be the
remains of an ancient caldera or crater.
The vast Koolau precipice from Nuu-
anu Pail to Waikane Is not the effect
of fault or breakdown, but Is entirely
produced by atmospheric erosion or
weathering. The prevailing and heav
lest transforms We're from the north
east, resulting in vastly greater erosion
on that side o. the range. similar re-
suit is conspicuous on the west side of
the Kaala range, and from like cause. !
There the east side of the mountain
was protected by the Koolau range
from the easterly rains, and the heav-
lest torrents of rain We're westerly, and
wore down that side of the mountain
even more completely than In koolau.
On page 30, DIR. Hitchcock briefly dis
cusses the limestone bluff at kahuku,
already considered by Dr. Dana in his
1, G,ats fgttt Vol
remarkable bluff, he says, consists of
coral rock up to 60 feet, capped by
blown calcareous sand now firmly con-
aolidated, which may extend inland to
height of $50 feet" Here we must
contradict the eminent geologist by
denying that any part of the bluff con !
slsts of coral rock" although traces of
corals exist, owing to it's long submer-
gence. The bluff is composed from top
to bottom of the same Illuminated loose
sandstone which pervades the ancient
and massive sand-dunes between Ka-
huku and Laie. Those dunes were hills
of brown sand which had been accu-
mulating for ages by reason of the
force of the trade wind sweeping
around and over the low angle of the
Kahuku mountain. Their sands had
become gradually cemented by perco-
lating rainwater into fragile laminat-
ed sandstone. This sort of sandstone,
which abounds between Kahului and
Wailuku, on Maui. is to be distinguish
ed from the very hard and compact
marine sandstone which takes fine
polish. The latter Is cemented by sea
water underneath deep sand beaches,
and is composed entirely of hard frag-
ments of sea shells.
Captain Dutton failed to distinguish
apart these marine and subaerial sand
stones, and thus betrayed into the
enormous blunder of imputing the
Wailuku and Waikapu sandstones to a
former period of submergence. whereas
they are obviously formed above wa
ter. and that district was plainly never
subjected to marine action. OF the Laie
shore are peninsula and an island
which are mtinly composed of the
same fragile Illuminated sandstone; but
this has become hardened by a later
submergenee. The land had evidently
sunk after the sand-dunes were Great
ed, but again emerged with the eleva-
ton or the coral reefs all around the
Island.
DIR. Hitchcock made special lnspee-
ton OF most of the secondary craters
frlnging the coast of Oahu, which be-
long to n comparatively recent period.
lie visited each of the Ave oratera OF
the Laeloa group which are located on
the Eva and Oahu plantations, and
whose widespread elections OF ashes,
now deeOmposed, constitute the exeep-
tionnl richness of the soil which yields
such unprecedented crops OF sugar,
Like the kaala mountain ON whose
nanks they rest, these cones are much
older than the Honolulu series from
salt Lake 10 koko Head, whose soft
tufa IL only partially eroded pr Hitch
cock, however, seems 10 impute
greater age Ia the latter, apparently
mlaled by Dall's erroneous assignment
II Diamond iiead % the Tertiary pc
Rod. =
with TINT conclusion Of "a ~ Dali
Ne are Rirenuoualy "a variance. lie
un Ia The kefy ancient llioefne period.
IL tries 8nake aul Thai The Aehaiis
anllldaa falid sheiisl Embedded ~ IN
nlaeelH ~ lha f0at uf Diamond Head
arn anfleHI lkpHa Whereas tie nknfll