The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1899-10-04


of an inch in extent would constitute q
/ severe earthquake. while in those q
most extreme violence the motion Ii
/ probably less than al foot. It is the sud
4 denness of the shake which breaks
4 buildings from their foundations
cracks theirswalls and causes the great
assures sometimes seen in the ground
THESE assures IN the ground vary in
width from narrow cracks, like those
Ecaused by the baking of the earth by
] the suns heat, to great rents two fee
j or more wide, and traceable for many
/ miles. Such rents in the ground have
been produced in peculiar cases, run
i ming for nearly 100 miles parallel to ar
\ adjacent mountain chain or to the
/ course of d river. If these caasnIs are
i deep enough and long enough they may
I become the channels of streams ano
! be worn by the action of the water into
rayines and valleys.
A violent shock will shake loose rocks
and earth from mountain sides and
overturn unstable fragments left by
4 the wearing of the weather. The exist
ence of such monuments as pinnacled
rocks, erosion columns and frail ratu-
! raj bridges, Is therefore an evidence
/ that the region In which they occur has
7 been for many thousands of years ex-
enipt from severe shocks. Springs are
temporarily disturbed, their flow being
either diminished or increased, and the
waters sometimes muddy or hot. Oc-
, casionally, too, nearly circular holes
open. in the ground and fill with water
/ 1t Is supposed that these are due to the
collapse Of underground caverns o.
! waterways.
In rare instances a. violent earth
quake has been coincident with con-
siderable permanent change in level of
/ the land, the change in level probably
7 being the cause Of the shock. This was
1 the case in the earthquake of 1922 in
/. South America, when the coast Of Chile
/ for a long distance was raised three
/ or four feet. In other cases, notably iii
a comparatively recent case associated
I with a violent volcanic eruption, nearly
the whole of large. islands in Asiatic
waters sunk beneath the sea with
thousands of the inhabitants.
Causes of Earthquakes.
While the phenomena and the super
fetal effects of earthquakes are very
evident to us, the causes which produce
these shocks are necessarily hidden and
can only be inferred or guessed. In
{ general however, it may be said that
they are due to the gradual cooling of
the earth, As the earth's substance
coois it contracts and its diameter very
slowly but surely becomes less. The
outermost portions which make up
what is generally called the crust have
already gone through this process SO
far that the crust cannot keep up in
contraction with the inner portions. The
solid crust is therefore constantly pull
ed down by it's own weight upon the
continually lessening interior. AS it is
too large for the interior and does not
fit, it must form wrinkles or oorruga-
/ HI,
the continents and ocean beds, and the
smaller ones constitute mountain chains
and the smaller inequalities of the land
This continent building and noun
tain building process has been going
on since the world began and had any
solid crust at all, is going on now and
will continue to so IN so long as any
contraction takes place.
The smaller wrinkles forming ranges
of mountains or hills do not grow with
such uniformity and sometimes not so
has been growing for ages may from
change in conditions in the interior
cease to grow. 1t may grow slowly
and gently, or this slow growth may
be interrupted by short periods of rest,
during which the rocks partially with
stand the pressure upon them, followed
by sudden yielding when the pressure
increases beyond the limit of elasticity
of the rocks. In this giving way of the
rocks to form the com 1aratively sharp
folds of mountains the outer portions
must slip on the inner portions, and
rupture of the rocks must occur before
such slipping can take place. Every
break in the rocks. whether large or
small, must give rice to an earthquake
of some degree of violence, and the
slipping of the jagged. broken portions
past each other will cause further
shocks Occasionally the rent thus
formed is filed with molten or, semi
fluid rock. and the injection of this rock
into the crack produces shock. Along
the ocean shores, where the older rocks
have become exposed by the wearing
of the weather and the waves, many
such faults may be seen. the rocks
sometimes rfven in many directions and
with almost countless cracks, every one
of which in it's formation must have
been the source of an earthquake.
In addition TO these less evident
causes it is easy to see that violent
volcanic action is likely to give rise to
earthquakes, the explosion and rear
rangement of matter beneath the sur
face setting UP vibrations which make
themselves felt in this way. Regions
which are known to be volcanic would
therefore be expected to be liable to
earthquake SHOCKS.
In North America there are records
of earthquakes Of some severity. In
1877 and the few years following there
occurred in Massachusetts long series
Of shocks, at first affecting a compare
lively large area, but soon becoming
confined to the town Of Newbury. which
they continued to disturb for more than
ten years. XII
In 1911 there began a series of shocks
of extreme violence ina region on
the Mississippi, with its center not far
below the junction of that river and
two years with such, violence that an
miles was lowered several feet below it's
original level Fortunately, this region
was SO thinIy settled at the time that
there were no costly buildings to be
destroyed and little or no loss of life
was caused; but a repetition Of such
shocks now would probably result in
the complete destruction Of many cities
and the loss of thousands of lives. Next
in violence to this earthquake is that
of Charleston, S. G., in 1856. This
shock, attacking a region where no pre-
uaration had been made for such in
stability of the ground. caused wide
spread damage. Wreolsing paris of the
city of Charleston, On the Pacific coast,
where earthquake shocks are, frequent
enough to compel preparation for them
and the adaptation of buildings to-
withstand considerable shaking, far
less damage would probably be caused
by a shock o. equal violence. Indeed.
III is interesting to note that in recent
shocks In San Francisco the tall build