It Is Now Well Ascertained That Almost All Volcanoes Have Been
Slowly Built Up By The Accumulation Of Matter - Mud, Ashes, And
Lava - Ejected By Themselves.
The openings or craters, however,
frequently shift their position, so that a country may be covered
with a more or less irregular series of hills in chains and
masses, only here and there rising into lofty cones, and yet the
whole may be produced by true volcanic action.
In this manner the
greater part of Java has been formed. There has been some
elevation, especially on the south coast, where extensive cliffs
of coral limestone are found; and there may be a substratum of
older stratified rocks; but still essentially Java is volcanic,
and that noble and fertile island - the very garden of the East,
and perhaps upon the whole the richest, the best cultivated, and
the best governed tropical island in the world - owes its very
existence to the same intense volcanic activity which still
occasionally devastates its surface.
The great island of Sumatra exhibits, in proportion to its
extent, a much smaller number of volcanoes, and a considerable
portion of it has probably a non-volcanic origin.
To the eastward, the long string of islands from Java, passing by
the north of Timor and away to Panda, are probably all due to
volcanic action. Timor itself consists of ancient stratified
rocks, but is said to have one volcano near its centre.
Going northward, Amboyna, a part of Bouru, and the west end of
Ceram, the north part of Gilolo, and all the small islands around
it, the northern extremity of Celebes, and the islands of Sian
and Sang-air, are wholly volcanic. The Philippine Archipelago
contains many active and extinct volcanoes, and has probably been
reduced to its present fragmentary condition by subsidences
attending on volcanic action.
All along this great line of volcanoes are to be found more or
less palpable signs of upheaval and depression of land. The range
of islands south of Sumatra, a part of the south coast of Java
and of the islands east of it, the west and east end of Timor,
portions of all the Moluccas, the Ke and Aru Islands, Waigiou,
and the whole south and east of Gilolo, consist in a great
measure of upraised coral-rock, exactly corresponding to that now
forming in the adjacent seas. In many places I have observed the
unaltered surfaces of the elevated reefs, with great masses of
coral standing up in their natural position, and hundreds of
shells so fresh-looking that it was hard to believe that they had
been more than a few years out of the water; and, in fact, it is
very probable that such changes have occurred within a few
centuries.
The united lengths of these volcanic belts is about ninety
degrees, or one-fourth of the entire circumference of the globe.
Their width is about fifty miles; but, for a space of two hundred
miles on each side of them, evidences of subterranean action are
to be found in recently elevated coral-rock, or in barrier coral-
reefs, indicating recent submergence.
Enter page number
PreviousNext
Page 7 of 219
Words from 3152 to 3672
of 114260
