Evening star., 1951-01-22
Coral AtoIIs Described
As Biggest of Structures
Naval Research Scientists Tell
Of Expedition into Mid-Pocifie
By Thomos R. Henry

Coral atolls are titanic bone piles.
They are by far the largest structures
ever built by living creatures.
This has just been reported to the
Office of Naval Research by scientists Of
the Navy-sponsored Mid-Pacif1c Expedi-
ton. This expedition. sponsored jointly
by the Scripps Institution Of Ocean
ography. made an intensive study Of the
war-celebrated Kwajalein Atoll, follow
ing similar studies three years ago Of the
Bikini atoll where atom bomb tests had
been conducted
Both these. it was concluded, consist
of remains Of coral and other sea Or
ganisms several thousand feet thick sur
rounding the cores of extinct volcanoes
which may be several miles high.
Compared to these enormous struc-
lures erected by living things over per-
iods of many milleniums. it is reported.
''the pyramids and the Empire State
building are microscopic"
There remains, however something in
explicable about the picture. Near Bikini
is one of the great sea mountains Of the
newly discovered mid-Pacific range.
Here volcanic rock was dredged from the
summit. Apparently the coral never had
been able to get a good start on its
building operations, although conditions
would seem to have been identical with
those on the other volcanoes. Several
large coral heads were photographed.
showing that the process had started and
was unable to continue.
Another inexplicable finding was that
the summit and sides Of Mount Sylvania
were covered with sheet Of the rela-
lively rare. lustrous gray metal. manga
nese. in almost pure form. Manganese
has a wide use in industry, especially for
alloying with steel. On land it is found
always in complicated compounds. 1t Is
quite similar to iron in most OF its prop
critics.
This sheet on Mt Sylvania was more
than four inches thick. On other noun
tain tops of the mid-Pacific range sheets
of about half this thickness were found.
A manganese cover over most exposed
rock surfaces in the deep sea is post
ulated. But how these thick layers were
built up puzzles the scientists. There is
hardly any of the element dissolved IN
sea water.
The manganese actually accumulates
in variety of ways. One Of the most
common is in the form of nodules.
round, rough-surfaced balls and irreg-
ularly shaped masses several inches in
diameter When one of these is cracked
open there always is found nucleus OF
something else, such as pebble OF VOL
canic rock, the ear bone of whale. or
the tooth of shark. In some cases
these are teeth of extinct shark species.
Rock Beneath Sediments.
Beneath the sediments which have ac-
cumulated for thousands of milleniums
on the sea floor. the expedition found.
there is a layer of rock through which
earthquake waves move at about $4,000
feet per second. This rock probably is
basalt, the same type which Is found
under the continents at depths OF ten to
Is miles. On land this is overlaid with
a great thickness of granite. This layer
is absent on the ocean floor.
The basalt shell of the sea bottom
is two to three miles thick. Beneath it
there is sudden increase in earthquake
wave velocity to $4,000 feet per second.
The increase extends all over the
world and marks the boundary between
the earth's crust and the heavy rocks
which extend downwards for 1000 miles
to the core of the planet.
curious feature found by the expe-
dition is that west of the Hawaiian
Islands there is an upper layer composed
of volcanic ash and debris where earth
quake wave velocity is much less than
through basalt This means that this
region of the earth can be considered
to have one extra layer.