New-York tribune., 1902-05-12
WEST INDIAN VOLCANOES

The calamity which has just overtaken two
islands of the WIndward group In the Antilles
will unquestionably lead to fresh discussion
Of the causes of volcanic disturbance. All of
the phenomena involved therein are not yet
fully understood and concerning some of them
there are perceptible differences of opinion
among experts On at least one point, however
there is general agreement. At a depth of
about thirty miles the internal heat of the earth
is probably great enough to melt every known
substance. Confinement may keep in a 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 upward
There is a growing tendency, moreover TO rec
ognize the Importance Of gravitaton in produc
ing eruptions. The weight of several miles of
rock is almost inconceivable, and II certainly
ought to compel potentially plastic matter to
rise through any crevice that might be newly
formed. Russell, Gilbert and some other au-
thorities regard this as the chief mechanical
agent In an eruption, at least when there is a
considerable Outpouring of lava.
AS to the extent to which water operates
there is some lack of harmony among vulcan
lists. Shaler, Milne and others hold that sub
stance largely, If not entirely responsible for
the trouble. They point TO the fact that many
volcanoes are situated near the coast of con
tlnents on islands, where leakage from the
ocean may possibly occur. Russell, on the
other hand, regards water not as the initial fac
tor, but as an occasional though important. re-
enforcement He suspects that when the molten
rock has risen to a considerable distance 1t
encounters 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 a state of powder and thus
originate the enormous clouds of fine dust
which are elected. Shocks of greater or less
violence also produced. The less severe
ones no doubt sound like the discharge of ar
tillery and give rise to tremors in the i'm
mediate vicinity. In extreme cases enough
force is developed 10 rend the walls of the vol
cano itself. Russell attributes the blowing up
of KrakatOa 10 steam. The eliminating episode
of the Pelee eruption last week, though not re-
sulting so disastrously to the mountain, would
seem 10 be due TO the same immediate cause
To this particular explosion, too it seems safe
to assign the upheaval which excited a tidal
wave
The precise manner in which the plastic
material inside of the terrestrial shell gets
access TO the surface is not entirely clear
Nevertheless, it is possible to get some light on
the matter. 1t is well known that in many
places there are deep cracks, or faults in the
earth's crust. Some of them in the remote past
have been wide and deep enough TO admit
molten material from below. The Palisades of
the Hudson are believed TO have been formed
by such an intrusion, the adjacent rock on the
eastern face having since been worn away by
the weather or other agents. II has been OBJ
served that many volcanoes are distributed
along similar fantS ba nf
OF volcanic islands in the West Indies suggests
the probability that it follows a crack of great
antiquity, though the issue of lava and ashes
Tor several centuries may have been limited 10
few Isolated points. Just how these vents
nave been reopened is one of the most difficult
questions still left for investigation. Given a
iihe OF weakness in the rocks though, and a
susceptibility to fresh fracture is afforded. Pro-
iessor McIee suggests that the overlooking of
'he ocean bed by silt from the Mississippi River
or other sources may have been the Immediately