The evening times. [volume] (Grand Forks, N.D.) 1906-1914, 1906-09-26
SCOTTISH VOLCANOES.
Research ut Rosyth Results in Some
Remarkable Finds.

\ rock section OF some seograph-
lcal interest may be seen on the new
/ railway OF Rosyth in cutting that
has been driven through the ridge at
llmpetneSS. on the west side of ST.
Margaret's bay. The rock in the i'm
mediate vicinity is whinstone; one
is surprised after penetrating the whin
a short distance to find strata of a
totally different. character. At the
west side of the section nearest Ro-
syth Castle there is Il large mass of
whinstone: abutting against this is Il
thick bed Of volcanic Turf which dips
to the east and passes under Il seam
OF limestone. The latter in turn is
overlarped by bed of shale. while
the outer facing on the east side of the
ridge is a sloping bed of trap rock
From its harsh feel. coarse texture
and mixed ingredients. this tuff may
be at once recognized as very char
acteristic example OF volcanic tuff or
asglomerate. 1t is made up of scoriae.
pumice and other fragn,entary ma
terials. such as are discharged by VOL
canoes and are often found filling up
old volcanic necks. Lines of strtaiti-
cation indicate that the constituents
Of the tuff owe their arrangement in
pes'e w WIG oSlAou vi lile waves vi
currents: they must. therefore. havS
been thrown out of a submarine VOL
cano or fallen in showers into water.
At the deepest part of the cutting.
where the ridge is the highest, ire
sistible evidence convinces the obser-
Yer that he is here practically inside
an old volvano. Scoriae and other
loose materials brought to the sur
face and piled up in cones afford proof
of the explosive character of an erup-
ton. Volcanic explosions are caused
by steam: seysers and volcanoes are
i'll all their essential characters alike.
except that the geyser discharges hot
water instead OF lava. AS molten roch
reaches the surface volumes of steam
escape, because Of the diminished
pressure. The bursting gas bubbles
also dissipate the fluid rock into i'm
palpable powder. which may be pro-
jected to IA great height and becomes
widely distributed by the wind. Vol
canoes of the explosive type discharge
comparatively little lava. and in some
cases none at all.
Bearing in mind that the volcanic
tuff is a superficial deposit of mater
ials produced by explosions. we can
form some idea of the conditions I'M
der which it was accumulated. The
explosive eruptions must have been
long continued to furnish materials
for deposit of this thickness. but the
period OF quiescence which ensued
after they ceased was probaly OF
much longer duration. for in the i'm
mediately succeeding layers of strata
no trace of volcanic action can be dis
covered. One of the peculiarities OF
volacnic agencies is it's Rip Van Win
kle character. Vesuvius remained in
active all through Roman history
down to 70 A. D.. when the eruption
occurred by which Pompeii and Her.
culaneum were overthrown. But 700
or even 1000 years would not go very
far to account for forty feet of sedi-
mentary rock. The time of tranquil
ity. however. came to an end at last;
the volcanic forces once more awoke.
but their character was altered. the
explosive being exchanged for the eff
fusive type: instead of showers of
stones and ashes great streams OF
terror of the earth. One feature in
the section is the remarkably even
outcrop OF I'll sedimentary beds, which
look as though thir ends had been
planned off to make a perfectly hori-
ZOuIdI SuIidCe. lie UlOSC pfODdDle
explanation is that it formed part of
the internal surface of the volcanic
vent, and that the ends of the beds
were saawn off by explosive blasts
issuing from the mouth of the VOL
cano. Up this inclined surface. too,
the stream of lava has been forced
and intruded over the shale. In any
case. the displacement has been sub
sequent to the intrusion of the trap;
the upheayal has affected tuff, lime
stone, shale. and trap alike. The
cause of this upheaval is perhaps to
be found in the upward pressure of a
great body of molten rock which at
a much later date found vent for it.
self through the loose materials form
ing the old volcanic funnel. and at the
same time greatly enlarged that open
ing The mass OF whinstone at the
west end of the cutting is memorial
| of this later outburst. Rising verti-
cally through the turf as an irregu-
ar column of unknown depth. it's in
trusive origin is obvious. Without
doubt the whinstone here is simply a
plug of lava left in the or fissure
through which long before the ma
terials of the turf and trap beds were
/ elected. The tunnels of many an
Gent volcanoes are found plugged
with lava in this way.-Edinburgh
Scotsman.