Durango semi-weekly herald., 1902-05-22
WEST INDIAN VOLCANOES.

The calamity which has just over
| taken two islands of the Windward
group in the Antilles will unquestion-
ably lead to fresh discussion of the
causes of volcanic disturbance. All
of the phenomena involved therein are
not yet fully understood, and concern
| ing some of them there are percep-
| tible differences of opinion among eX-
perts. On at least one point how
ever there is general agreement. At
a depth of about thirty miles the in
| ternal heat OF the earth is probably
Great enough to melt every known
substance. Confinement may keep
in rigid condition the material which
| lies beneath the solid crust, but if
an avenue of escape is once opened
the stuff would soften and ooze up
ward. There is growing tendency.
moreover. to recognize the importance
Of gravitation in producing eruptions.
| fhe eight of several miles of rock
is almost inconceivable. and it certain
ly ought to compel potentially plas-
tic" matter to rise through any crevice
| hat might be newly formed. Russell,
'iip'it anu sOiht olitl duliiOii illtS It-
gard this as the chief mechanical
agent in an eruption at least when
here is a considerable outpouring of
lava.
As to the extent to which water op-
crates there is some lack Of harmony
| among yulcanists. Shaler, Milne and
others hold that substance largely if
not entirely, responsible for the trou-
ole They point to the fact that many
volcanoes are situated near the coast
Of continents. or on islands where
leakage from the ocean may possibly
occur. Russell on the other hand
regards water not as the initial fac
or. but as an occasional. though i'm
portant, Reinforcement He suspects
hat when the molten rock has risen
20 a considerable distance it encoun-
ters that fluid. perhaps in a succession
Of pockets, and that steam is then
suddenly generated. The explosive
effects which ensue, are of two kinds,
BY the expansion of the moisture
which some of the lava contains the
latter is reduced to state of powder
md thus originate the enormous
LIQUIDS of fine dust which are elected
Shocks of greater or less violence are
llso produced. The less severe ones
10 doubt sound like the discharge of
trtillery and give rise to tremors in
he immediate vicinity In extreme
ases enough force is developed to
rend the walls of the volcano itself.
Russell attributes the blowing up of
he Krakatoa to steam. The culmi-
lating episode of the Pelee eruption
| last week. though not resulting so dis
lstrously to the mountain, would seem
to be due to the same immediate
cause. To this particular explosion,
90, il seems safe to assign the up
Ieaval which excited tidal wave.
The precise manner in which the
plastic material inside of the terres-
| trial shell gets access to the surface
g not entirely clear. Nevertheless, it
| is possible to get some light on the
natter. 1t is well known that in
! many places there are deep cracks or
faults" in the earths crust. Some of
| hem in the remote past have been
vide and deep enough to admit molten
| material from below. The Palisades
If the Hudson are believed to have
been formed by such an intrusion. the
| adjacent rock on the eastern face hav-
ng since been worn away by the
weather or other agents, 1t has been
observed that many volcanoes are dis
tributed along similar faults.
| The existence of a chain of volcanic
islands in the West Indies suggests
the probability that it follows crack
Of great antiquity, though the issue OF
| lava and ashes for several centuries
nay have been limited to a few isolat
I'd points Just how these vents have
been reopened is one of the most diff
cult questions still left for investiga
ton. Given a line of weakness in the
rocks. though, and a susceptibility tc
fresh fracture is afforded Professor
McGee suggests that the overlooking
of the ocean bed by silt from the Mis-
3issippl river or other causes may
have been the Immediately exciting
,ause of the recent outbreaks. Othel
biologists have found a similar -ex
planation acceptable In the case o
eruptons elsewhere. The theory has
much to commend it to favor.
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