The Hawaiian star. [volume] (Honolulu [Oahu]) 1893-1912, 1901-03-28

disturbed that precise uniformity of
projection as to have piled the falling
tuf in irregular positions. The beauti-
full symmetry of the crater is a power
full witness of it's sudden and rapid for
nation. 1t forbids any other concep-
ton.
My second evidence of the brevity of
the eruption which created the crater
cone is derived from an arithmetical
computation of the time required to de-
post the actual mass of the cone by a
fountain of adequate height to deliver
its ejecta upon the existing rim of the
bowl Data are easily secured for
sufficiently approximate estimate of the
time to show that 1t could have oc-
cupied a very few hours at most. Let
us first compute the solid contents of
the tuff deposited. The average diam
eter of the bowl is about 900 feet. Two
thirds of the perimeter is $50 feet high,
to which so feet may be added on ac-
count of the average depth of sea at the
distance from the shore where the erup-
ton occurred. The other third of the
perimeter was occupied by a conical
mass probably 1000 feet high, but
standing in perhaps $50 TT. depth of sea.
Estimating this cone as 1850 feet high
with 5000 feet diameter of base, it's
solid content would be about 5000, 900, =
900 cubic feet The contents of the
other two-thirds of the perimeter would
be about 5000, 900 cubic feet making
with the cone a mass of $4,000, 000, 900
feet of tuff in the entire crater.
A similar result is obtained by as
Stunning a base equivalent to 5000 feet
square, and an average height of 500
feet which gives a solid content of
twelve and a half billions of cubic feet,
1t is evident that such an estimate is
sufficiently large.
Now, to have elected the whole mass
in five hours would have required an
emission from the vent of two and a
half billions of cubic feet of tuff in an
hour, or of 694,44 feet in one second.
Surprising the vent to have a sectional
area of 1000 feet, which I believe to be
much too small, the velocity of ennis
sion would be only 347 feet in a second,
which is equivalent to a theoretical
height of only 1000 feet of projection
aloft. 1t is evident that this is totally
inadequate. Assume then only two
hours duration of the eruption. This
gives us S75 feet of velocity of emission
equivalent to a height of projection of
1925 feet Such an altitude of the
fountain might be adequate to the ac-
tual distribution of the ejecta to an
average distance of $500 feet from the
vent. But it must be noted that the
height attained with the assumed velo-
city could hardly be more than two
thirds of the theoretical one, on account
of the resistance from the falling tuff
encountered by the ascending jet. 1t is
also evident that the fountain must
have been a very lofty one for the
tuff to have been driven mile to tho
leeward by even a heavy gale, as so
much of it was done in building up tho
massive cone.
The real area of the vent can be lesq
accurately estimated. The partially eX-
posed vent of the neighboring crater of
Punch Bowl is apparently fully hun
dred feet in diameter. The only COM
pletely open vent of the kind which 1
have seen is that of Kalaupapa at the
leper settlement on Molokai. This is a
rocky well with vertical sides reach
ing down to salt water, which is 800 feet
deep. The diameter if this well or
shaft was, as I remember it, from 100 to
$50 feet. Guided by these data I should
consider 5000 square feet as a very con-
sentative estimate for the sectional
area of the shaft from which issued the
tuff of Diamond Head, instead of the
1000 feet assumed above. Such in
creased area would reduce the two
hours duration assumed, to 4S minutes.
1t would be much less if we allow a
greater velocity of election, so as to
get a height of the fountain adequate
to allow of it's extensive detection by
wind. 1 incline to the belief that the
eruption did not last more than half
an hour. 1t is absolutely impossible
that it could have continued many
hours.
These explosive eruptions are Of
gigantic force and brief duration.
Honolulu, November 14th, 1900.