Essex County herald. [volume] (Guildhall, Vt.) 1873-1964, 1886-09-24
CAUSE OF EARTHQUAKES.
A GEOLOGICAL EXPLANATION OF
THE PHENOMENA.
Number and Geographical Disuribu-
ton of Shocks in North America
Last Year.

Major Powell, Director of the United
States Geological Survey, says: During
1885 there were recorded the following
earthquakes in the United States and
Canada: Canadian Provinces, eight;
New England, five; Atlantic States,
nine; Mississippi Valley, three; Pacific
slope, thirty-four; total, fifty nine. Dur
ing the twelve rs-1S12-S3-there
have been recorded in the United States
and Canada 1854 earthquakes, distributed
as follows: Atlantic slope, 147; Missis-
slppi Valley, sixty-six; Pacific slope, 151.
From this list it appears that in the en-
tire area earthquakes occur on an average
once in twelve days and once a month
on the Atlantic slope. Many of these
disturbances are, however, so slight as to
be unperceived by the ma iority of the
people, and it should be observed that
the list is more complete in the densely
populated and frequently shaken Allan
tic slope than in either the seldom shaken
Mississippi Valley or the sparsely popu-
lated Pacific slope.
The explanation of earthquakes usually
accepted by the biologists is something
like this: The earth is believed to be
inclosed by q solid crust of rock of vari-
able thickness in different regions. This
crust rests upon material in a more or
less fluid condition, so that it readily
yields to agencies of reformation
like water or molten iron. The
reasons for believing that the
interior is in a somewhat fluid
conditions are various. The most i'm
portant are From very many observa-
tons made in mines, artesian wells, etc.,
it is discovered that there Is ancrease of
temperature from the surface downward,
and that this increase is so great that a
degree of heat sufficient to melt all
known rocks is soon reached. 2. BY
certain geological agencies certain rocks
from below are brought to the surface in
mountain building, and these rocks show
evidence of having been greatly heated,
and even of having been melted. 3
Molten matter in very large quantities
comes up from the interior of the earth
through crevasses and volcanic vents. Be-
side these lines of evidence there are
many accessory facts woich tell the same
story. The interior of the earth is con-
stantly losing heat in variety of ways.
A small amount is probably conducted to
the surface and radiated into space. A
large amount of heat is conveyed from
the interior through the agency of hot
springs. Such springs are found in many
portions of the known earth, and i'll a
few districts are very abundant, and
through them heat is conveyed from the
interior to the surfare, which is there ra-
dated into space. The lavas that are
brought up yield vast stores of heat, all
of which is lost to the earth through IA
diation. The secular cooling which re-
suits from the above causes must neces-
sarily diminish the magnitude of the
earth, and as it shrinks the solid exte.
rior crust must in some manner yield SO
as to conform to the lesser magnitude
thus produced.
The stresses produced in the crust of
the earth by the shrinking of the interior
are modified by another class of agencies.
The land surface of the earth is washed
| by rains and rivers, and in the aggregate
large bodies of material are carried away
and deposited in lake bottoms, which
are gradually filled up, and especially
dCpOSlUCIl dlOuS ILC ollOIOo VI I1O 0Soo'
The unloading of land areas and the
overlooking of certain water areas to q
large extent LOCALITIES it. Again the fluid
or plastic material of the interior changes
its position beneath the crust of the
EARTH and portions of it flow out as lavas
thus an additional set of stresses is estab
lished. Thus stresses are established
through the agency of a contracting in.
terror through loading and unloading at
the surface and through the flow of in.
terror matter to lava beds, where sucf
matter is poured out upon the surface
The stresses produced by the various
agencies thus described gradually become
so great that at last the crust of the
earth must yield and earthquakes are
produced.
The occurrence of earthquakes in the
eastern portion of the United State!
seems to be related in very interesting
way to certain geologic facts observ d il
the region At least a considerable
share of the Atlantic slope earthquake;
are suppo ed to have sequential con
necton with line of displacement pass
ing through the Carolinas, Virginia
Maryland, Delaware and New Jersey
This line of displacement has for som,
time past been a sub ;ect of investigation
by the Geological Survey. In Georgit
and the Carolinas it is represented by
general seward fitting of the surface
unquestionably connected with subter
rancan movements, and in Virginia thi
widespread fitting begins to concentrate
in definite line of displacement which
In the latitude of Fredericksburg, is I
gentle monoclinai, j. e., the rock strat'
are there locally bent downward, anC
here as well as elsewhere along the dis
placement the land toward the sea is de
pressed, and that toward the mountain
is elevated. In the latitude of Washington
the displacement becomes either clos
feXure or fracture, and lies in the east
ern branch. Its amount here is 80 feet
At the head of Chesapeake Bay the dis
placement is 100 feet, and it appears t.
increase northward, reaching 200 or 30
feet in the lower Hudson Valley. Tn
whole of this movement has probabl
occurred in post-quaternary times, and
still in progress; indeed, it may be ques
toned whether any general orographi
movement on any part of the earth
surface during any period of geologi
time has been much more energetic an,
rapid than that now taking place alon
the Atlantic shore; and our comparativ
immunity from serious earthquakes her
is to be attributed, not so much to ali
sence of these great earth movem ents
resulting IN the formation of mountai
chains and even the npheaYal of cont