The Hawaiian star. [volume] (Honolulu [Oahu]) 1893-1912, 1901-03-28
A SHARP QUICK ERUPTION
DIAMOND HEAD PILED UP IN
HALF AN HOUR.
Dr. Bishop In the American Geologist
Seeks to Prove it by Figures-Errors
of DR.. Dali.

The leading article on the American
Geologist for January is an article en-
titled "Brevity of Turf Cone Eruptions"
by DR.. s. +. Bishop of Honolulu. The
article is one of local as well as of
scientific interest and is here reprinted
by permission.
Tuff-cones, of which a number have
been formed on the eastern coasts of
the island of Oahu, are produced by the
class of eruptions distinguished as lex
plosive." The semi-liquid tuff has been
projected in a jet or fountain to a con-
siderable distance and having been
driven literally by the expansion of
the steam and other gases contained,
has fallen at some distance from the
vent building up cone with a more or
less regular rim enclosing a concaVe
| bowl. All the explosive eruptions &C
tually observed seem to have occupied
very brief time. The greatest one,
| that of krakatOa, was probably less
than one hour in actual emission, al
though the fall of it's lighter ejecta
continued for several hours.
1t therefore seems remarkable that an
! opposite opinion should have been eX-
pressed respecting the eruption which
produced Diamond Head. This typical
| tuff-cone, lying in the suburbs of Homo
lulu, bounds our ocean view to the east
ward. 1t was recently examined by
Doctor w. II. Dali of the Smithsonian
age of the fossil shells found in its de-
bris. In the Bulletin of the Geological
Society of America" Volume IL, PIP. 81
co. DR.. Dali expressed conclusions res
pecting the age of the crater which l
feel obliged to controvert. He says:
THE conclusion to which came was
that the whole mass of Diamond Head
had been slowly deposited in compare
lively shallow water and gradually ele
waited without being subjected to not
able feXure. The election of material
at first must have been intermittent
with long quiescent periods to enable
the shore to have become repopulated
with mollusks and corals." good
picture of Diamond Head appears OPP
posite page 40 preceding.
1t is necessary here 20 remark upon
two serious errors of observation COM
mtted by DR.. Dali 1t is true that Dia-
mond Head was deposited in shallow
water its center being about one mile
outside of the previously existing shore
line. l undertake, however, to question
the idea that it has since been ''gra-
dually elevated" Such elevation if it
occurred must have been some 200 feet
to have exposed what he calls marine
formation on it's seward base DR..
Dali should have observed the total alb
sence of marine erosion around the
sides of the cone, upon the soft mate
rial of which the action of the waves
would have been etremely destructive.
There is also no trace of such erosion
around the evidently older tuff-cone of
Punchbowl four miles away, nor any
elevated beach marks along the neigh
boring mountains.
DR.. Dall's second error of observation
was in attributing a marine origin to
the mass of material lying against the
seward base of the crater That mass
is composed of mingled small angular
L,
heights above, with large quantities of
calcareous beach sand. Pervading the
mass are numberless laminated calca-
reouS concretionS, which DR.. Dali has
mistaken for coral reef. These fragile
laminated cruStS are identical with
those forming the interior structure of
our numerous calcareous sand dunes.
The layers constantly vary in angles of
dip, corresponding to the formerly
varying surfaces of the dunes. Had the
tuff enclosed ever been exposed to the
action of the waves so far from retain
ing it's angular forms, it would imme-
diately have been ground into soft mud.
The whole mass is of Aeolian forma-
ton. 1t is simply a great sand-dune.
The contents have been assorted by the
wind the eastern end being composed
mainly of larger fragments of tuff,
and the western end, one-third mile
away, mainly of sand much triturated,
and stained by the brow tuff. The
mollusks of Tertiary age enclosed in
the mass, as found by Dr. Dali, may
be fully accounted for as having fall
| len from the heights with the tuff. They
We're torn off from the ancient sub
merged reefs and beaches traversed by
the shaft of the eruption. l have found
large shells embedded in the laminated
tuff at KokO Head, as well as coralS.
Farther evidence is found in the fact
/
/ between the crusts in great numbers
side by side with the marine shells.
Both fell together from the cliffs above.
My main contention, however, is to
prove the absolute impossibility that
crater like Diamond Head should be a
product of intermittent election" with
| "quiscent periods" even brief ones, or
that it could have been Slowly deposit
| ed" l propose to prove that a cone of
such peculiar form and structure could
have been created only by an extreme
| ly rapid projection aloft of it's material
completed in a few hours at most and
ceasing suddenly and finally.
| My first proof of this conclusion is
! derived from the extreme regularity of
the elevated circular rim of this cone,
such as could be the result only of a
| single rapid, uniform. unidentified
| outthrow of the tuff. Two thirds of the
elevated perimeter is part of an al
| most perfect circle or ABOUT 6,UUU feet IN
diameter, and of a comparatively uni
! form height, about $50 feet above sea-
= level The tuff is piled up in this reg
ular ridge, originally rounded on it's
! top, in very uniform quaquaversal lay
ers or laminae, whose steepest dip on
! the outside is about $50 and much less
on the inside of the broad bowl. The
great subaerial erosion discloses the
! interior structure of the rim, although
| it has not ObliteTated the really delica q
| symmetry of the original form
The southwest third of the perimeter
! of the crater is massive, attaining a
present height of 1862 feet. 1t is severely
wasted by the impact of storms, and
was once probably 900 feet high. The
! original rounded summit must have
been considerably to seward of the
present sharp peak. The original form
may be best understood by comparison
| with those of Koko Head and of Lehua
! island, which are of somewhat similar
form and dimensions, but remain sub