Evening star. [volume] (Washington, D.C.) 1854-1972, 1897-07-10
SUBMARINE EARTHQUakEs.


ARE similar Ia Those on Land.
From the London STANDARD
earthquakes formed an important tonic
In the interesting lecture which Prof Insn
Milne delivered to the ROYAL Georraph,rsl
society last night. though he was aealir,,
with the wider subject of the changes
which &C on beneath the sea. There Vas
thus melancholy appositeness I'm his re-
marks, for each successive telegram from
india brings worse and worse accounts of
the recent seismic disturbance there. I.arye
districts have suffered more or less severe.
ly about Calcutta. Madras and Bombay
but the devastation in Assam is now
stated to be on a far greater scale. and II
is probable that the worst is not Vet
known.
But Prof. Milne as We have said. was
discussing more comprehensive quo stion
the movements that take place ''in the
silence OF the central sea" We have long
been aware that even here the earth is MOI
absolutely at rest. Tiny organisms fan.
IKE perpetual drizzle, on the ocean floor:
ea,th gust, Vet more minute. sinks grad
uaiiy Gown through the water but this
ooze accumulates with extreme slowness
Besides this, the floor itself may bs. nm
hited or depressed, but these movements
aiso had been supposed TO be very gradual
so much that they could moi he ,le-
tected, could hardly be inferred directly
from any observations made by man Prof
Milne, however. shows that there are occa-
slonally very significant hints of what is
going on. and that now and then nature
moves more abruptly than some of us sup
pose submarine cables indicate uneN-
pected disturbances; now the gutta percha
is melted, as IL by heat: now the cable is
broken, as though by a strain: now IL APP
pears to have been buried by mud slip.
There are IL seems. two sets of causes
which produce movements beneath the
surface of the sea The one is the slow
foldings, fractures and crushings of the
crust-causes on land which have produced
mountain chains and conspicuously
recorded on their rocks. The other is the
effects Of erosion and sedimentation. The
removal OF material from one place as
from a seaworn coast, and the deposit of
II In another, produce exactly the same
result as the piling up of materials else
where would do-namely. unstable con-
tours, which may ultimately cause move
nents Of various kinds. In other words.
there may be landsips below the water
just as much there may be above IL,
and from not dissimilar causes. Both these
kinds of influence probably affect larger
areas. There is third, but more local
lied, modifier of the sea bed-the sub
marine volcano. All three may produce
earthquakes, the first especially. Bent
rocks may at last break under the strain:
one or both parts of the divided mass may
start forward, as 1t were. with jump;
myriads of tons of rocks are set in motion,
and a shudder is propagated through the
earth's crust, which, when IL originates
beneath the ocean, may shatter cities on
reaching the land, and may raise huge
waves. that come sweeping along the
coast, bringing death and destruction TO
the lowlands. The first Jerk may not toe
the only one; again and again. if the crum-
bling process continues. new slips may
occur along the line of fracture, and fresh
shocks be propagated through the crust
One special object of Prof Mines lecture
vas to point out the circumstances in
which these disturbances are most likely
to occur. An earthquake and movement of
some kind stand in The relation of effect
and cause. Sometimes this movement is of
an explosive character, and the shock is
directly connected with volcanic action. but
perhaps more often-the latter also
stands rather in the relation of conse-
quence to movements tending to wrinkle
the earth's crust Prof. Milne. during his
residence in Japan-a veritable land OF
earthquakes-took some pains to ascertain
whether the shocks were started in the
mountain region or beneath the sea, and
found that out of 40 shocks less than one
sixth had originated inland, more than
half beneath the ocean, and the rest near
the coast, and even Of these a good many
had come from the sea Besides this, he
has observed that wherever the land de-
scends rapidly beneath the surface OF the
water whether from the coast line or into
an ocean basin, there earthquakes are like
ly to originate, while gentle slopes are rare.
" the sites of disturbance. slipping OF
materials also occurs mueh more easaS ~,
the former case. SO that here disturbances
Of all kinds become more probable. In me
Northern part of the Indian ocean there Is,
we may remark. a rapid deepening OF the
sea bed, and on either side mucn accumu
iation Of material. Whether the recent
EARTHQUAKE has any connection with the
.swatch of no ground" cannot be known
till more precise details have been receiNeu
and compared but Prof. Mines remarks
on the general question show that TINS is