New-York tribune., 1906-04-22
EARTHQUAKE THEORIES.

The recent convulSiOn of nature the Pa
cific Coast has revived the discussion of the in
fuences which bring about such phenomena
Earthquakes fall into two general classes. One
TO be associated with volcanic eruptions in
point of time and geographically The other
class is not The tremors observed on the island
OF Martinique four years ago, when Pelee was
disturbed, illustrate the first variety. The Ques
ton then arises whether the shocks in Califor-
mia could have been related in any way to the
outbreak Of Vesuvius a week or two before.
Professor Matteucci has been credited with say
ing that the two might be effects of the same
cause but he was careful not TO suggest that
one was the cause of the other. He probably
meant to hint that the same kind of forces, act
ing locally operated in both places, and not that
one event was in any sense connected with the
other. 1t has been observed that the great ma
jority (if not alb of the volcanoes on the globe
are distributed along creyces in the rocky crust.
Such localities seem to be the scene Of the worst
earthquakes also. If anything occurred to re-
oper an old issure, to admit water to the
heated interior of the earth, an explosion would
follow, and if a convenient vent was available,
steam, ashes and perhaps lava would be elected
from It. On the other hand, a disarrangement
Of strata along fault" might occur where the
other requisites to an igneous demonstration
were lacking A REIMBURSEMENT of the position
of the rocks would be accomplished only by
overcoming friction and other resisting agencies.
and more or less vigorous vibration would be
excited.
Professor Stevenson, high geological author
ity, suggests that there may have been re-
newal Of subterranean activity among the ex-
tinct craters of the Sierras. The old outlets
there being sealed, the mechanical energy which
was suddenly developed might possibly (he
thinks) have caused the disturbance on the
coast This is certainly an interesting con-
lecture, and is not TO be rejected hastily, but
the distance between the mountains and the
scene of the observed disturbance warrants a
little hesitation in accepting the notion. Indeed,
ii is TO be observed that Professor Stevenson
mentions It with caution and as only one Of
several possible explanations.
Several curious theories have been ad-
vanced TO account for the strains to which
earthquakes give relief. 1t was once suspected
that the moon excited tide in the fluid in
terror of the earth. A limited number of OBJ
servations encouraged the view that there were
more shocks when the earths satellite was in a
favorable position to operate in that manner
than at other times. According to Major Dut-
ton, perhaps the best American authority in
such matters, the statistical preponderance dis
appears when a larger number OF earthquakes
is considered. The supposition that the earth
Is composed Of a shell whose contents are liquid
Major Dutton also dscredits the belief that the
shrinkage of the interior from the radiation of
heat has been sufficient to set up stresses in
the crust serious enough to explain the phe-
nomena in question.
Mr.. Milne, an Englishman, who has accu-
mulated much data In regard to earthquakes.
suspects that there may be some relation between
them and the wabbling of the earth on its axis.
! The latter eccentricity has long been known to
]
| derstood. Mr. Milne thinks that it may be
| climatic, differences in the load of Ice and snow
at the poles from year to year making the axis
tilt more at one time than another Mr. Milne
holds the maximum stage of solar activity as
l indicated by sunspots, responsible for the tenn
perature changes here represented: and Sir
/ Norman Lockyer, a prominent astronomer,
evinces confidence in the possibility. There are
several weak points in the chain of reasoning
Of Mr.. Milne and Sir Norman, but the weakest
/ is the supposition that the wabbling motion Of
the earths axis could produce the effect which
they impute to IT If they fancy that the swing
could cause variations in the intensity OF the
I attraction exerted by other celestial bodies on
| the earth's interior their belief would seem TO
/ have no more justification than the now dis
carded theory Of lunar influence.
There are much simpler ways TO explain the
strains which, il is generally conceded, give rise
10 shocks like those which have just caused
| desOlation on the Pacific Coast Inland there
| are enormous mountain ranges. The ocean bot
! tom slopes downward rapidly off shore Thus
incalculabe differences of pressure exist on the
earth's interior. These are permanent in char
/ acter, though they act intermittently. Then
| from the Sacramento and San Joaquin valleys
| there is a steady transfer of solid material TO
| the sea by huvial action. The effect Of this
! agency IS gradual and cumulative but many
| biologists consider it adequate to cause dis
! location" earthquakes.