Evening star. [volume] (Washington, D.C.) 1854-1972, 1931-06-29
BY H. RIES,

Professor of Geology. Cornell University.
Copyright 1881. by the Associated Press
ITHACA, N. Y, June 29.-Geology,
instead of being a dry science of dead,
uninteresting rocks, rapidly is coming
into everyday life, because of its prac-
teal value. Mere reference to its use
fuiness in engineering and structional
work, or its assistance in opening the
doors to the worlds vast supplies Of
mineral wealth, point to this
AS wealth producer its greatest re-
cent service probably Is in locating
petroleum and gas fields. The geologist
has recognized that oil and gas favor
certain geologic structures, and the To-
cation of these is carefully plotted In
the field. An interesting sidelight is
the investigation of the source rocks
and migration of oil and gas.
on Is not usually found in the rock
where 1t originated. so our problem Is to
learn what the source rocks are. We
are getting data on this from a study
OF modern marine sediments, determin-
Ing which types yield the most oily
matter.
We know that fnost oil is derived
from plant material. and a study of
certain black shales of New York State
shows that some of this rock was de-
posted under fresh-water conditions
and some under saltwater conditions
We find that more oil can be distilled
out OF that portion Of the deposit which
represents marine, than from that
which is freSh-water deposition. We
have found, also. that 1t is probably the
very lowest forms of plant life that pro-
duce oil.
Source Rocks Differ.
The source rocks often appear to be
black shales, but all black rocks, even
though they contain altered plant ma
terlal, are not source rocks The point
is that in some cases plants decay to
form coal and in others form oil
The geolcgist also has found that the
OIL migrates from ITS source bed into
the reservoir rock where it is now
found, and this problem also is being
attacked to determine what causes il
to migrate and how far it might travel.
AS an interesting sidelight it has been
found that If finely porous rock filled
with OIL is next to a more open one
filled with water, the latter. because
OF its greater adhesive qualities, will in
wade the light rock and force the oil
into the more open one. In general,
Oil and gas migrate from the source
rock to the nearest open rock.
In engineering work, geology has be-
come of great assistance. 1t has be-
come highly important in building dams
and reservoirs. since the dam must be
located on strong, water-tight founda-
ton. and the reservoir should not show
excessive leakage. These factors all are
controlled by geologic conditions.
The construction of the Catskill
to New York City called for the solution
OF many geologic problems Not the
least interesting of these was the cross
ing of the Hudson River, where the
aqueduct had to pass under the river in
solid rock. The biologists knew that
the Hudson River had carved a deep
gorge when the land stood at a higher
level. and that since then there had
been sinking of the region, and part
OF this gorge had been drowned"
Furthermore it might have been deep
ened by glacial erosion.
Depth Is Determined.
We had then drowned valley partly
filled in by soft deposits, and it was
necessary to put down a line of bore
holes and determine the depth to bed
rock. This was found to be not less
than 900 feet. and the tunnel was car
ried across at a depth of LOO feet.
Dlderent rocks exhibit different de-
sLecS Oh udTCneSS ana SOundneSS, thus
affecting tunneling operations. Some
can be penetrated rapidly, others but
slowly; some require little support,
others much. The geologist can make
study Of the mountain to be tun-
neled through, construct a geologic
cross section and thus determine before
hand, approximately at least. the kind
and amount of each rock type to be
removed.
Many large structures bear down on
the foundation material with tire
pressure. If the latter were
not strong enough to bear the weight
OF the building it would simply slide
from under and let the structure down,
Engineers nowadays often make bear
ing tests Of the foundation materials.
Geology also is useful in locating
underground water supplies, for we
know quite well the geologic conditions
which favor the storage of water under.
ground. Its first practical use probably
was in endeavoring to locate ores. for
1t came to be recognized that the acclI-
of valuable metals in the
earth's crust were due to now well rec
ognlzed geologic processes.
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