The Austin weekly statesman. (Austin, Tex.) 1883-1898, 1889-05-16
FORMATION OF ISLANDS.
THEIR CREATION DUE TO VOLCANIC
eRUPTIoNs AND OTHER CAUSES.

Scientific Information Not Given in the
GeoGraphies-Islands Which Have Been
Blown Tn from the Oceans Bottom.
Detached Pieces of Land.
Your ordinary text book of geography,
.'as she is written" talks barely and BADLY
about the size of countries, their boundaries,
their rivers and lakes, capes and head lands,
their populations, their religions and their
chief products. These are all facts, no
doubt; but they are facts which resemble
pearls destitute of any string whereby they
NAV be converted into a necklace and thus
made useful and ornamental both. My be-
lief, therefore, leads to the assertion that we
should become more scientifc-but not there
by less popular-in our geographical teach
ing in schools; and this very subject OF Islands
shows the way of reform. Science, in this
sense, dives below the bare facts of the text
books, and seeks to give reasons for these
facts. 1t places itself in the position of an
expositor and expounder of the manner in
which our world and its affairs have come to
assume their existing order.
Geographically, all islands are regarded as
of much the same constitution. They are de-
tached masses of land, surrounded by sea,
and differing to the mind of the schoolboy
or schoolgirl, chiefly in SIZE Australia is
big island; Madagascar is not so big, and
from Ceylon onward to Mauritius or the
Azores there are found all degrees and grada-
lions of magnitude. This, with few details
about the quarters Of the world in which
islands exist, and with some ideas about pro-
ducts and peoples, complete the geographical
| knowledge of the average man and woman.
Science takes DIP the matter where common
| place geography ends its story. 1t asks, first
Of all, what islands really are, and how one
island differs from another. As a result of Its
| Investigations, science soon discovers that
| islands may be divided by their nature into
| two distinct sets or classes. Of these two
| divisions, the first includes islands which can
| lay claim to that title from the first day OF
their existence, in that they have never
! formed part and parcel of any larger mass of
| land. Thus we first distinguish the SO called
''volcanic" islands, which, like the Azores,
have been thrust up from the sea depths by
| volcanic action, to form detached masses OF
| land existing, it may be, many miles from a
| continent or mainland.
Then comes a second class of islands which
are called continental" because, whatever
| their size form or situation, we can prove
| them to be geologically part and parcel of
bigger tract of land. They are separated and
| disioined fragments, so to speak, of a larger
| land mass. Under this head are to be included
many islands we know The British islands
are simply detached parts of the European
continent; just as Trinidad is q fragment Of
| South America; or as the Malay archipelago
represents the broken up land which, once
| upon q time in its hale and solid state, con-
| nected Asia and Australia. Even New Yea
| land and Madagascar are continental islands
in their way, although the exact dates of
their separation may be very hard to trace in
the mists of geological time.
| THE DIFFERENCE SCIENTIFICALLY EXPLAINED
Having thus succeeded in distinguishing
between islands which, like ST. Helena, the
| Azores, the Galapagos and SO forth, represent
| the eruptions into the narths outside mass of
volcanic matter, and those which, like Brit
| ain, Trinidad and the Nest Indies, are really
the detached pieces of la"ge land tracts, it be.
| hooves us to inquire further into the history
of each group. They are separated from
their mainlands it may be, by abysses of
| ocean. On the other hand the continental
islands have, relatively, shallow seas separat-
| ing them from their nearest continents.
Witness, to provo this statement, the Ger
man ocean, the English channel the sea be-
| tween Trinidad and America or the general
| depth of the seas around the Malayan ISL
ands. We find test not only of the nature
of an island in the depth of the seas around it
apart from its rock structure-but in the
case of the continental islands we can assure
ourselves of the length of time they have
| been separated from their mainlands by hay
| ing regard to the same matter of ocean deep
| ness.
The Azores, as volcanic islands, are thus
separated from Portugal by sea varying
from 1000 to $500 fathoms. Within a short
distance from the islands themselves the sea
is about 1000 fathoms deep; within 500 miles
it is 1,SOO fathoms, and soon deepens to $780,
With the Bermudas the case is similar; some
$50 miles off we reach the sea bottom at
3,S25 and 3,S15 fathoms st. Helena has sea
of 2,SGO fathoms deep between it and Africa,
some 100 miles off. Centrariwise, the sea
around our own shores is comparatively shall
low; but, as | have remarked, whenever a
continental island shows, like Madagascar, a
| ueep Cuinuei UeCNSeu III anu us HILL llLIl,
the story such depth tells us is one of long de-
tachment from the mother country
PLANT AND ANIMAL LIFE.
So far, islands have shown us that geologic.
ally their history is interesting in respect of
the marked variation between the two classes.
Not less interesting is the additional evidence
about islands which their animals and plants
have to tell Whence, let us ask, have de-
tached islands, like the Azores, obtained their
animals and plants3 Upraised from the sea
bed, as have been these islands, their living
population must have been derived from
other and previously peopled lands. This sup
position is confirmed by our finding that on
the Azores we discover no animals or plants
excluding those of mans introduction
which are not found on the Portuguese coast
The rabbits, weasels mice and a single kind
of lizard found in the Azores are importa-
tions.
The birds which, Of course, can ay over the
intervening sea, are those of Europe; such
also are the insects, and such, again, are the
plants. In word, there is nothing about
the animals and plants of the Azores which
we cannot explain by reference to their Eu-
ropean origin Then also, on such detached
islands, we cannot expect to find native