Bismarck daily tribune. [volume] (Bismarck, Dakota [N.D.]) 1881-1916, 1912-08-27
ISLANDS OF CORAL
True Ones Only In the Pacific
and Indian Oceans.
THE GREAT BARRIER AToLL.

This Famous Coral Reef, or the Aus.
tralian Coast, Is the Largest In the
World and Extends For Thousands
Of Milss-Bsrmuda's Worm Tubes.
There are no true coral Islands In the
Atlantic. The coral islands OF the Pa
cltic and Indian oceans are very dis
tinct from the SO called coral Islands
Of Bermuda and the West Indies.
True coral islands, or atolls. are
formed by corals building upward on
a submerged reef or peak until the
growth reaches the surface Of the sea
or so near It that broken pieces Of coral,
drift, sand, etc, accumulate ana In
time build an exposed islet. At other
times the coral reef Is raised above the
water by volcanic action. The Pacihc
reefs are often circular or semicircular
In form. and such reefs are known as
atolls.
The largest coral reef Is the Great
Barrier reef Of Australia, which en-
tends for several thousand miles.
The cora. islands Of the Atlantic are
formed by wave broken shells and bits
Of coral which have become soliditied
and fossilized by chemical action and
age. This material Is known rs aeo'
liam limestone and after exposure to
the mir is exceedingly hard and dura-
bic, but where freshly broken or cut
It Is very soft and can be chiseled ana
| sawed into blocks for building pur-
poses.
Many Of the West Indian coral Is
lands are partly composed OF FOSSIL
| coral reefs which have been raised far
above the present sea level by the vol
canic uplift of the rocks to which they
were attached. Such coral reefs, says
! the American Boy, are often found
| hundreds of feet above sea level and
In places are found alternating with
layers Of lava. showing that the is
lands have been raised and submerged
| several times in the past.
The atoll.llke reefs in Bermuda are
not coral ut all. but are formed OF In
Vulnerable worm tubes belonging to
certain annelids. These worm tubes
are often thickly incrusted with other
growths, such as coraline, seaweeds,
bryozoa, corals, etc, and thus have the
appearance of being composed OF real
coral.
Corals, when alive. IRE not white, but
are Of many beautiful and vivid shades
Of green, pink, red, brown, yellow. Law
ender or orange.
A mass Of living %corals, when seen
through the wonderfully clear waters
Of the tropical sea, Is a very beautiful
and brilliantly colored sight. There
are a great many kinds Of coral. Some
are rounded and massive and are
known as brain corals." Others are
broad ard spreading or branched, while
others are delicately formed and very
brittle. Others are covered with rose
shaped or star shaped markings and
are called "rose" or star corals."
The openings or indentations in any
coral mark the spot where a coral ami
NAL lived. The animals or "polyps'
are very similar to sen anemones In
form and have numerous tieshy tenta-
cles, which may be drawn In out OF
sight when danger threatens. The en-
tire coral Is covered with animal mat
ter when alive. and It is only after I'LL
the flesh Is removed and the skeleton
Is bIeached that the white coral ap-
pears. All the corals mentioned are
known as "stony corals."
Another very large group Of corals Is
the horny c%orals," or Gorgonias. The
we'll known "sea fans" as well as the
"red coral' used for jewelry, belong to
this group. .
Corals are not all confined to tropical
seas. There are numerous species
found as far north as the Grand banks
Of Newfoundland and Greenland. but
these are not the reef building species,
but belong to groups inliabiting the
deep sea. One species Is quite COM
mon on the coast Of New England, but
Bermuda marks the northern limit Of
reef building species in the Atlantic
Exchange. .a. y..
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