El Paso herald. (El Paso, Tex.) 1901-1931, 1916-03-18
Former Canal Geologist Says
This VIII Not Injure
The Canal.
CAUSE OF THE
NUMEROUS SLIDES
Ocean Bottom Is Sinking
Gradually Outside Isthmian
Waters, Says MacD Donald.

DANAMA, March 1S.-That the Pan
anna canal will not be swallowed
up by an earthquake in the future
and that the troublesome slides now
being encountered will eventually be
conquered and the great waterway
made an unqualified success, is the
opinion Of Donald +. Macdonald. for
merly canal geOlogist and now mining
~geologist FOR the United States bureau
Of mines.
Mr.. Macdonald. who spent several
years on the isthmus making a care
full study as to fragility of the earth's
crust, has just made an official report
TO the effect that, while. through seis-
mic disturbances the whole isthmus is
rising at the rate of three feet every
hundred years. this will not necessarily
injure the canal. As far as he sees,
IL viii merely mean a little additional
expense in The dredging OF the big
waterway.
ocean Bottom sinking.
The cause OF this rising, he says, Is
the sinking Of the ocean bottom out
side the isthmian shore waters. Every
time there is a little movement Of the
ocean bottom. the isthmus, t. be in har-
mony, Joins in. de also suggests that
IL the rising motion be rapid. tnen there
would be serious danger for the canal.
but, that from what has happened in
recent geologic time, 1t may be con-
cluded that the canal is not in any ap-
probable danger from the instability Of
the isthmian land. The rising of the
isthmus, however, has been responsible
FOR the many slides that hav been en-
countered, in that the motion OF the
ground has dislocated and crushed the
rocks, leaving them weak and unstable.
any rate" says Mr.. Macdonald,
so far as the digging Of the Culebra
cut Is concerned, these faults have in
creased the cost Of the canal several
million dollars.
CuIebrn Cut Difficulties
a TO the slides. Culebra cut is a
vast ditch that passes through many
varieties of rock in the min miles Of
its length. Some of these are weak
M unstable, and where the slopes Of
the cut were steep and 100 to 800 feet
high the weaker rocks crushed down to
Tatter slopes. Whenever the slope got
flat enough, the sliding stopped. AT
no time did the engineering staff con-
structinE the canal believe that the
slides were a menace to the ultimate
completion and successful operation OF
the canal, in spite Of the fact that at
times they were somewhat troublesome.
They have made necessary the eXcava-
ton Of about 80, 000, 900 cubic yards
more han was included in the first
estimate for Culebra cut, but they have
not in the past and will not in the fu-
ture endanger the ultimate success Of
the canal
Mr.. Macdonald calls attention 70 the
fact that one is apt to forget that the
greatest variation OF atmospheric pres
sure near sea level may be more than
four million tons per square mile and
that if the adjustment OF atmospheric
pressure in a very large ave or mine
lags behind any quick increase in at
mOspheric pressure at the surface, a
considerable strain may be added to
the roof Of such an excavation.
Discussing the real OF the slides
Mr.. Macdonald declares that in many
cases the immediate cause was the
oversteepness and height Of the slopes,
the blasting n other work attribut-
able only to man. He adds that the
geologic conditions were not suffi-
clently considered in the first plans
for digging Culebra cut.
Gntun Rocks solid.
As the strength Of the famous Gatun
dam has been brought into question on
a number Of occasions, Mr.. Mcdonald
refers 20 il i'm some length. at was
found that the Gatun rocks are rela-
lively solid and compact and suitable
for foundations for heavy structures.
However. some writer's, even recently.
have affirmed that the Gatun rocks
would soften into mud when Gatun
lake filled. and thus the locks and dam
would sink their foundations and be
damaged or destroyed. Opinions OF