The Pacific commercial advertiser. [volume] (Honolulu, Hawaiian Islands) 1885-1921, 1906-04-22

80 >c>c>c>c>
piles of huge clots and lava flows with
comparatively little or almost no frag-
mental beds. The other volcanoes thus
far referred to have yield, as rule
silicious and ropy or viscous lavas. good
material to confine steam until it bursts
: with explosive violence The Hawaiian
lavas are almost exclusively basalt;
they are therefore more fuSible, more
fluid when fused, and less adapted
to yield tufts. While there is no lack
of emitted steam during eTuptions, and
While clots of lava are blown high in
the air. yet the principal product of the
vents is a great liquid tide which
breaks through some rent in the side
of the crater or lower down the noun
tain, and which may flow nearly fifty
miles.
The craters, moreover, are different.
Instead of comparatively narrow
throat, from which as from a safety
valve. the escaping steam roars hoarsefy
into the air, we find great pools or lakes
of molten rock, upon the surface of
which sheets of CONCEALED lava form
and disappear like evanescent ice on
water, or which are surging and boil
ing as the vapors rise from the depths
and float away in the air. The height
at which the lava stands varies from
1 time to time. 1t has been observed
with differences of 500 feet or more in
the same crater.
There are two craters which have
been active in recent years. One, Maui
ma Loa. with its great altitude of
1856 feet. is not easily reached: the
other, Kilauea, on the TANKS Of Mauna
Loa, is only 1000 feet above the sea,
and is the one most frequently visited.
It's relations with Mauna Loa present
one of the most significant of volcanic
phenomena. 1t would seem that since
these two vents are on the same island
and but little more than twenty-five
miles apart, they must draw their
supplies of molten rock from distinct
and separate reservoirs. else the lower
vent would tap off the upper.
While the remaining islands of the
Hawaiian group are all volcanic, yet
they do not possess cones which have
been active in the historic period.
They remain as the evidence of former
outbreaks the accommodations of which
have been carved by waters into many
interesting land-forms.
THE SHIFTING OF VOLCANIC AC-
TION.
Few portions of the world have en-
tirely escaped the effects of volcanic ac-
ton or it's closely related manifestations.
In some the cones. though now cold
and dead. yet look as sharp and clear
as if their eruptions were a thing of
yesterday. In some the work of air
and water has so dissected and laid
bare their Utmost structure that it is
from the dead we learn most of the
living. OF still others only the stumps,
1.-The once deep-seated portions, are now
visible. Craters, lava sheets. and bikes
have long since been washed as sand
and clay into the sea.
Before the advent of life upon the
earth, so far we can judge from the
remains a great belt of volcanoes ran
along the Atlantic from Newfoundland
to North Carolina. The summer visit
or at Mount Desert may not always
know that underfoot are ancient beds
of volcanic ash and pumice not so
very different, except that they are
tightly cemented together, from those
which have lately destroyed st. Pierre:
nor may the guest at the South Noun
tain of Pennsylvania, as he looks across
the beautiful and fertile Cumberland
valley, realize that the hills about him
are old-time lavas. Even such unlikely
places as central Kentucky and central
New York are not entirely without
their dfkes of eruptiye rock. while the
region about Lake Superior must have
been once a scene of enormous volcanic
activity. Many thousands of feet of old
lava flows are piled one on the other
in the copper district, and many square
miles of ash beds and sheets are in
the Marquette iron range.
The same relations hold good abroad.
Iceland seems to be the expiring CUTLER
of a huge volcanic belt now extinct in
the Scottish Isles. The Auvergne in
France has been the delight of the
geologist since the science began.
Among its cones. SO beautifully pre-
served. one may almost say geology
had its birth. The Rhine valley. Bo-
hernia. and Hungary TEEN with evi-
dences of the work of the interior forces
of the earth. and if we pass Asia
and Australia their striking exhibitions
are no less pronounced.
T3E CAUSES OF VOLCANOES.
The great fundamental proposition
upon which the explanations of vol
canoes rest is that the earth grows
hotter from the surface toward the
center. The rate varies, so far as re-
liable data indicate, from so to over
100 feet for a degree Fahrenheit. The
former. which is nearer the average
of the earth. and # we pass 10 Asia
than the latter. would mean about 1902
in the mile. The radius of the earth
is nearly four thousand miles. Less
than one per cent. of this would mean
from 10000 to 40000. Ordinary lavas fuse
at temperatures of from 2200' to