Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-12-24
VALUE OF OCEANS
BED IS REVEALED
Importance of Nature OF
Land Undersea Stressed
by Repairs.

Eight cable repair ships tossing on
the turbulent Winter Atlantic, spending
weeks mending the strands of wire
broken in a few seconds by an under
water earthquake. emphasize the i'm
portance to mankind of the land that
lies hidden beneath the worlds most
travelled ocean," says bulletin from
the headquarters of the National Geo.
graphic Society.
floor OF the Atlantic before the work of
laying the first cable was begun in 1857.
Later, in the 1905, came careful ocean,
cgraphic surveys by British, German
and American scientific expeditions, and
gradually the world gained a knowledge
of the unseen basins and valleys, the
ridges and plateaGs and mountain
ranges that make up the floor of the
Atlantic. The practical work of the
cable ships in connection with the lay
ing of the 81 cables that now cross the
North Atlantic has filled in many of the
details.
When the first effort was made to
connect Europe and America by cable
in 1857 the most favorable underwater
route was chosen largely by accident be-
cause 1t happened to lie under the mar
rowest portion of the North Atlantic.
Depths Vary Sharply.
Later surveys disclosed the existence
OF an underwater plateau in this region
between Newfoundland and Ireland.
The depths over this upland range from
little over a quarter mile to 21a miles,
This seems deep enough, perhaps, to the
layman, but short distance to the
south and to the northeast are depres-
sions between and miles deep.
THE underSea upland that stretches
across from Newfoundland to Ireland
was recognized to be SO valuable for
cable-laying purposes that it was named
Telegraph Plateau Not only is it an
asset because of the relatively shallow
water and the resulting comparatively
low pressure to which submerged cables
are subjected, but the very nature of the
material Of the bottom is such as to
help protect the cables. 1t is soft
ooze formed from the rotted shells and
skeletons Of innumerable small sea crea-
lures, which serves as a cushion and a
protective covering for the cables.
In the early days of the cable lay
ing, when the technique of manufactur-
ing the cables had not been developed
and when they were neither so strong
nor so well insulated as they are now,
the Telegraph Plateau was invaluable.
Now cable making has advanced to such
point that it is possible to make cables
so sturdy and well insulated, that they
can be laid in water 4 or miles deep.
There the pressure amounts to several
tons per square inch instead of the Is
pounds per square inch that materials
are subjected to above the surface OF
the sea.
when laying cable at such depths
| the weight of the cable from ship to
bottom causes a tremendous pull. It is
still markedly cheaper to make cables
| for moderate depths and to lay and
maintain them there.
Telegraph Plateau" Invaluable.
Fourteen of the twenty-one cables
that now cross the North Atlantic make
use of the Telegraph Plateau but the
other seven have been plunged boldly
into the deeper waters of the NORTH
American Basin, where the bottom lies
miles and more below the surface
| These depths are encountered by the
four cables that extend from Nova
Scotia and Newfoundland to the Azores
by the two that extend directly from
New York to the Azores and by the one
which strikes across the Atlantic from
Cape Cod to Brest, France.
Just how an underwater earthquake
breaks cable is not clear. Theoretical
ly break either in the cable or its in
sulation might be caused by sideslip
the opening of crevasse, the dropping
away of a portion of the bottom, the
| sudden rise of a section Of the ocean
| bed, or by a landslide from some ocean
peak or bluff. Probably only very severe
earthquakes can break cable. The
average earth tremor of the land sur.
face which rattles dishes and even