The Pacific commercial advertiser. [volume] (Honolulu, Hawaiian Islands) 1885-1921, 1894-01-13

The immediate vicinity Of Homo
lulu offers to the student OF historical
geology many most interesting prob
lens. The origin of the soil OF Homo
lulu is one of these. Elsewhere In
Hawaii nei the soil consists gener-
ally, except in the valley bottoms,
simply of decomposed lava, fragments
of the unaltered rock everywhere
encumbering the ground. Here and
there only do we find areas OF deep
soil free from stones. These are
mostly in nearly level regions, where
FREQUENT rains have favored the rot
ting of the rock to considerable
depth, while the amount OF rainfall
has been insufficient to carry of into
the ocean the disintegrated rock. In
few cases a deep soil has been
formed from decomposed volcanic
sand or gravel, which has been spread
nv an explosive eruption over large
area of land. Honolulu owes its fer
tile gravelly soil to an occurrence OF
this kind, 80 recent that much OF
the gravel remains still undecom-
posed. 1t is easy to see that the re-
markable group Of cinder cones just
back of the city are geologIca!ly
quite new Loose as IS the material
composing them, erosion has made
little progress as yet In scoring their
sides, in spite of such flooding rains
as we have had twice within ten
months past-upwardso OF five inches
In each storm.
Additional proof of the regency of
the eruption or eruptions which
heaped them up is found In the pres.
ence in portions of the tufa forma-
ton at the base of Tantalus OF salt
in large quantity, although the loca-
ton is one where the soil Is kept
constantly damp by frequent rains,
and there must be rapid drain on
the salt supply, as the fresh rain
water percolates through the tufa.
The salt itself, I think it may be as
sumed. has come from sea water, ad-
mitted into the assure which formed
at the time of the eruption, although
il seems remarkable that water 80
admitted should find vent at so great
an elevation and at such distance
from the sea. The tufa of Diamond
Head is also impregnated In places
with salt. one of the spots being near
the very top of the cone, and In this
instance there would seem to be nc
question as to how it came there.
There is another incidental evil
dence which / may mention OF con-
nection of the sea with the eruption
in Makiki, in the large amount o.
calcareous matter that has been de
posted here, apparently from hol
- springs. There Is near the Mak1k
fall bed of rock many feet in thick
ness, consisting of volcanic grave
cemented together with calcium
carbonate. 1t is In fact this ledge o
hard rock which has made the fall.
Now our volcanic rocks contain 81
small a proportion OF lime that L
does not seem likely that water, ever
at a high temperature, would dissolv
ont from them sufficient OF that min
eral to account for any such deposit
The water which came up through
the coral formation underlying Dla
mond Head we know was hlghl
charged with lime, and we may rea
son that this water also came throug
assure traversing coral rock 1t
noticeable that in both instances tn
carbonate of lime is accompanied ais
by phosphate, but this Is very com
mon association of minerals.
When these large mounds OF vol
canic sand were piled up some or tn
same material was widely scattered
falling over the region to leeward, q
far as the harbor on the west, an
Punghou street on the south, be
mainly IN the line of the trade wine
passing Lunalilo Home, the powde
magazine and the south shoulder {
hiQp
sand on the side OF Punchbowl an
In its crater was from this source
from Punchbowi itself, and go olde
is not quite certain. That such mat
rial occurred among the ejecta fro
that crater is beyond doubt, as ma
be seen by examining the expose
strata In the gap on the east side
the cones. 1t is hardly probab!
however, that any such formation
remain now superficial.
The mouth of Makiki valley mu
have been closed by the sand hea
the stream thus damned up after
time cutting through the obstructiC
which was In places fifty feet or mo
in depth, and spreading the sal
thus removed over the fiat belo
Query, was this fiat at that time st
submerged? / have found no whe
as yet conclusive evidence of this.
am inclined to believe that the erU
tions were coincident with the chan
of level which made it dry land
The wash from the hill sides
also carried down much gravel a
scattered it in similar manner,
that the plain is covered to del
of five to fifteen feet over an ext
sive area with the debris, from VIII
has been formed deep rich soil.
Where this debris has been cut Il
bystreams or bitches, there are fou
frequently in it deposits OF calcs
Gus matter, either in crusts as froI
hot spring, or In vertical seams,
Lot