Evening star., 1939-01-17
Of Stars, Men
And Atoms
Notebook Of Science Progress
In Field, Laboratory
And Study

In FIeId, IoDoTotory
And Study
By Thomas r. Henry.
The Atlantic Ocean has risen and
fallen $4,000 feet in the last 10000 years
while man has inhabited the North
American Continent-and Is now close to
one of its high-water marks.
Evidence for this conclusion has been
presented to the Geological Society of
America by 1t. Comdr. Paul A. Smith
of the Coast and Geodetic Survey and
DR.. A. C. Veatch of New York City. It
is based on exploration of the submarine
canyons of the Atlantic, including the
mile-deep Hudson River gorge lying 5000
feet below the sea surface, and the Congo
River Valley of the coast of Africa.
These great underwater cuts, it is be-
lieved, were made by streams flowing
into the ocean during a period of low
sea level.
"The ancient shore of the ocean," says
the report, was 100 miles or more beyond
the shores of today and must have been
near the edge of the steep declivity which
is called the continental margin. AS the
glaciers disappeared from the continents,
not only in North America but over all
the regions of the earth buried under
their loads. the water making up these
great ice sheets was restored to the sea
in sufficient quantities to raise the sea
level about 260 feet to approximately its
present height.
Shortly after this the ocean again
receded, not only to the ancient shore
at the edge of the continent, but even
farther seaward, exposing the sleeper
slopes of the continental margin and
laying bare the 10O-mile coastal shelf as
a plateau, standing more than 10000
feet above the sea. The Hudson, follow
ing direct course probably similar to
the ancient one which carried the load of
mud and sediment that it has spread
over these valleys few thousand years
before, when they were submerged, again
pushed its wide, shallow channel across
the great plain and cut the mightiest of
all canyons on the steep slope in the
same soft silt and sand it had previously
laid down.
This canyon probably began as a
rather modest valley. but it was cut head
ward and shoreWard until the deepest
part of the bottom now lies more than
1000 feet below the rim, and 1000 feet
below sea level. In this great gully we
could stack up the Empire State Build
ing and the Chrysler Building one on
top of the other and they still would be
covered by more than 1000 feet of sea
water.
"Other present-day land streams of
the Atlantic Coast also found their way
through various channels across the
F, broad plain of soft sediments which had
been gnaWed and smoothed previously
by the hungry waves Of North Atlantic
storms, and reaching the steep decl 'ty
roared down the slope, cutting more and
greater valleys"
Another clue to the rising and falling
Of the Atlantic, the report points out,
has been found in the Congo submarine
SoAAy SAi oAAA VAlC SOll6O OdSlll Ill AlIlCd.
This river once flowed westward through
valley now lost somewhere in the i'm
penetrable rain-forest jungles of equa-
torial Africa. The older valley was
damned up by an upheaval which raised
a high enough range of hills to stop the
river completely. The impounded waters
rose and crept eastward to flll the great
Congo basin and form an extensive lake,
driving off human inhabitants of the re-
gion. The presence of man before the
formation of the lake is proved by find
ing human artifacts buried in the silt
and sediments which once formed the
bottom Of this great sheet of water.
Eventually the water spilled over the
lowest edge of the basin and formed the
| present course of the Congo River. This
new outlet cut its way down through the
rocks of the rim until the old lake was
drained. Recent Portuguese surveys, it
was pointed out, show another vast SUBJ
marine canyon with characteristics quite
similar to those of the Hudson, which
extends more than 10 miles into the
estuary Of the Congo. This canyon is
known to extend many miles out into the
Atlantic. 1t has been concluded that this
submarine canyon, as does that of the
Hudson, dates back approximately 20 900
years..
What world-moving force or astron-
omic event caused the Atlantic Ocean to
vacillate between an ancient shore, IL 900
feet below the present level is a contro-
versy Of comparative unimportance to
the marine surveyors of the Coast and
Geodetic Survey" concludes the report.
"Soundings made by the slow and tedious
process Of lowering a weight to the bot
tom of the sea first indicated IS years
ago that the Hudson submarine canyon
existed. Since then the Coast and
Geodetic Survey has developed and per-
fected many modern gadgets to speed up
and increase the accuracy of its surveys,
| in order to keep pace with growing de-
mands of modern navigational aids. Out
standing among these developments are
radio acoustic ranging, sono-radio buoys,
and Improvements in echo sounding.
With these new devices the survey has
been able to extend the marine surveys
from our shores to the limit of our con-
tinental borders with such accuracy that
| outward or homebound ships, equipped
| with echo saunders, can determine their