The Hawaiian star. [volume] (Honolulu [Oahu]) 1893-1912, 1901-07-22
CUTTING DOWN TINE LIMIT.
DIR. BISHOP MAKES QUICKER
WORK THAN EVER.
VIII Now Not Allow More Than Four
teen Minutes for the Making of Dia-
mond Head-New Proofs.

EDITOR STAR: A few months since
you kindly reprinted from the Anne
rican Geologist" of February my short
article on "TheVelocity of Turf Cone
Eruptions," in which l presented evil
dence that the eruption which built up
the Diamond Head crater must have
lasted less than one hour.
l beg leave now to present a new line
of evidence ,corroborating the former
proofs. 1t may be remembered that the
leading proof of the extremely short
time occupied by the eruption was an
arithmetical one, based upon the height
of the formation of hot mud or rock
paste necessary to distribute the ma
terial over half a mile each way-also
the necessary velocity of election to
reach that height-1000 feet in second.
The area of the shaft or vent of issue
of the fountain was estimated very con-
servatively at 5000 square feet making
out-throw of five million cubic feet in
a second. A liberal estimate of the en-
tire mass of Diamond Head seems to
be 1880, 900 900 cubic feet. To eject that
amount, Therefore, only $500 seconds
would be employed, or a little over forty
minutes.
My new line of evidence, which tends
still more to lessen the length of the
eruption, is one which seems to prove
that the sectional area of the vent must
have been several times 5000 square
feet. If so the time occupied indis-
charging the twelve odd billions of
cubic feet would be proportionately
shortened.
This evidence is based upon the i'm
mense quantity of calcareous or limey
deposit prevailing the tuff Nominations
of the crater-cone. This lime must
have been derived from the coral reefs
through which the eruption tore it's
way. 1t was torn off from those reefs
nv 10 nd vic
of the election.
l think we can approximately esti-
mate the bulk of this calcareous
element prevailing the tuff. II is best
observed closely along the new road
inland of the crater. 1t forms thin
incrustations upon the surface of every
Elimination of the tuff. This condition
apparently exists in every part of the
cliffs throughout the whole structure.
1t seems to me an extremely moderate
estimate that the lime constitutes one
2O0th or .005 of the whole mass. That
gives us over sixty million cubic feet
of lime torn out of that short portion of
the vent-shaft which traversed the
coral beds fringng the island.
l suppose that 1000 feet will be con-
sidered a very large estimate of the
thickness of those coral beds, which
have gradually grown up as the island
subsidized. Sixty million divided by two
thOuSdllu gives US OV,UOU 5IluelCe ICel as
the sectional area of the shaft torn out
of the coral.
10000 is six times the 5000 foot area
assumed in my previous article. 1t
would reduce the forty minute eruption
to only seven minutes lnration. But as
on the other hand. the vent SHAFT would
have begun of smaller dimension, en-
larging as the minutes wen; on, we may
properly allow double the above time
or fourteen minutes for the whole dur
alton of the tuff-fountain.
OF course, l do not claim any sort of
precision for my premises either as to
the proportion of lime in the tuff, or as
to the depth of the coral reef. But the
figures and results are at least, sugges-
tive. The dimensions of the vent were
doubtless, much larger than the 5000
feet assumed in my former article.
Punchbowl vent seems to be much
larger than that
The limey incrustations appear to
contain no traces of coralline structure
l judge that the coral was entirely
melted and volatilized by the intense
heat
S. f. BISHOP,
Honolulu, July % 1901.