New-York tribune., 1902-05-14

Vlscous iquid-masses of the liquid rock are
down INTO th6 air. and falling build up
RIM or crater about the place of discharge.
commonly the lava in the summit portion of a
condult becomes chilled and perhaps hardened,
ana When a steam explosion occurs this crust
Is shattered and the fra agments hurled into the
ar and contributed to the building of the walls
OF the 1nclosing crater The products OF
ploslVe volcanoes are vapor and gases molten
rock and solid rock. The Vapor is steam aud
Ihe gases in certain instances, at least, largely
1ree hydrogen and free oxygen. The explosions
allhough commonly ascribed to the violent es-
cape OF steam, may in part be due to the union
Oh the oxygen and hydrogen present. The liquid
IoCA escapes as streams or lava-fows and in
part Is blown into the air. The liquid or plastic
proJectles produced in this may be-
coIne suHlclently solid to retain their form
strlklng, and are termed volcanic bombs. They
IIequentiy have a spindle shape, with twisted
ehds, showing that they rotated while in rhe
ar about axis; but in oIher instances they
natten on striking. and may even be so nearly
lqulo that the material composing them spreads
ouI as thin cake when it comes to rest Bombs
are frequently found several miles from the
NoIcano that elected them, and f1attened and
even thin lava cakes are sometimes abundant at
distance of one two miles from the place
Where they began their aerial journeys
ne soma rock blown out by volcanoes consists
usually OF highly vascular material which
hardened on the surface of the column of iaya
Wlthln conduit and was shattered by explo-
slons 6eEeath it. These fragments vary in size
from uust particles up to masses several feet
IN diameter, and during violent eruptions are
hurled miles high The larger fragments COM
l.
~ iurhlsh the principal part of the material OF
which craterS built but the eraveI-like ker-
nGIs, i, IapllH' may be carried lateraly several
nIlles II wind is blowing. while the dust is
frequently showered down on thousands Of
square miles OF land or sea. The sclid and usual
~ angular fragments manufactured in this man
hot falling ''''- '
Volcanoes of the explosive type not uncom-
monty dlscharge streams of lava, which may
now many miles. In certain instances these ont
MelIings gs or liquid rock occur after severe earth
quahes ana violent explosions, and may have
an CHe CHARACTERISTICS of quiet eruptionS There
Is thus no fundamental difference between the
Two types into which it is convenient to divide
volcanoes "
MOONTAlNS BLOW THEIR HEADS OFF.
In extreme examples of explosive volcanoes,
ue summit portion Of a crater perhaps several
f iIIeS IN circumference and several thousand
rect nigh, is blown away. Such an occurrence
~ recorded III the case of the volcano Caseguina
Nicaragua, IN 1850. or. entire mountain may
disappear, being reduced to lapilli and dust and
IN TioWn t INTO the air as in the case of Krakatoa.
III the Strait of Sunda, in 1888
The essential feature of a volcano as stated
above Is a tube conduit leading from the
IsnIy heated sub-crust portion of the earth
70 the surface, through which molten rock is
forced upward TO the surface. The most marked
NaIlaIonS IN the process depend on the quan-
uy or molten rock extruded, and on the free
in the lava 0''''''N
The cause of the rise of the molten rock in a
volcano is still matter Of discussion Cartain
geologlsts contend that steam is the sole motiva
power while others consider that the lava is
IClceu 10 the surface owing TO pressure on the
reservoir from which il comes The view Der-
maps most 1aNoraby entertained at present in
reference To the general nature of volcanic erlIf
ohs is that the rigid outer portion of the ca rtb
becomes fractured, owing principally 10 move
HeitS resulting from the shrinking of the cool
tH6 inner mass. and that the intensely hot ma
leIid reached by the assures. previously soIid
o"lHs 10 pressure. becomes LIQUID when uressura
- renewed ana is forced TO the surface As the
Hoi'el material rises ii invades the wafer
nan Seu rocks near the surface and acouiras
StsaIl' OF the gases resulting from thu. dec0npo-
Sluoh or water, and a new force is added which
P4ouuces the most conspicuous and at times the
tiOnS. P""Si"s eEuP-
i, me recent volcanic outbreaks on Martinique
ana st Vincent We're eruptions Of tbe eEyI,sii,..
SPe' similar 10 the explosions that hay. nc
NuIieu from time to time in Vesuvius The vol
canoes nave been dormant for wears ana +ba
ava IN the summit portion OF their conduits
Ootu ana nara. movements in the earth's crust
caused "a fresh ascent OF lava from deep beIov,
Tue surface. the molten material came in CON
tact with water in the rocks IL invaded and
steam explosions resulted. ~
1hese explosions were similar a. what would
happen II water should be poured on "A rna ss
OF molten Stag such comes from an iron fur-
mace Inc succession OF events recorded in hun
dreds OF instances has been repeated Although
the recent erupuons have been disastrous on ac-
count or their proximity 10 cities and thickII in
hablted rural districts, they appear from tha
inledsTe accounts available. to have been small
IN intensity in comparison TO many other sin1iIar
occurrences which have taken place