Los Angeles herald., 1907-02-03


The island OF Jamaica has a ieculiar
geographic position in that It lies al
most In the center Of a great intra-con-
tinental oceanic basin OF the type Of the
Mediterranean sea. This American
Mediterranean as Il is often called, is
formed by the Gulf of Mexico on the
one hand and the Caribbean sea on the
other. The basin is nearly enclosed by
q rim Of land and by chains OF islands
or shoals within which it descends to
abyssmal depths comparable to those
of the great oceans. IL Is from the CEN
ter of this miniature ocean that ia
maica rises up and to this peculiar po-
stion is due the fact that whatever dis
turhanCes or relative changes of level
of land and sea occur In this basin,
they are most strongly felt on this is
land, while the rim of the basin may
scarcely be affected at all
Jamalca's Connguration is varied It's
eascrn third is dominated by the great
Blue Mountain ridge which rises to
an altitude of 1860 feet IN the central
scrrated ridge. The eastern face of this
ridge Is an abrupt descent to the sea.
while its western slope Is a gentle one.
passing into the much dssected plateau
region which forms the great part of
the island The appearance of this
ridge has been aptly compared to a
much crumplcd handkerchief picked up
by the middle These mountains are
carved out OF the oldest rocks of the is
land bat their age is not SO very great,
geologicdllN speaking, for they belong
to the later Mesozoic or secondary per-
Tod Of the earths history-to the age
when chalk was forming in western
Europe, and when giant water reptiles
swan the ocean which then covered
Kansas and Nebraska, and monstrous
dinosaurs wandered up and down the
Atlantic coast of the United States.
Early Volcanic Activity
1t was at this period of the earth's
history that Jamaica was a center of
much volcanic activity. Great masses
of volcanic debris accumulated upon
shallow sea floor of a le"el piedmont
plain of wide extent. Rolled about by
streams descending from the mountain
sides, or by waves on the shore these
fragments We're worn into rounded peb-
bles and boulders which now form n
part of the solid rock material of which
these Blue mountains are formed.
Sands and clays. the latter preserving
fragments of the vegetation which
clothed the mountain sides of that time,
were deposited upon the boulder beds.
while repeated volcanic outbreaks of a
milder sort spread layers of volcanic
ashes over this region. Then this whole
series of strata, probably mile in
thickness, was crumpled up and raised
into one huge mountain system of AL
pine magnitude and compleXity. This
was the first greet revolution which af-
fected this region subsequent to the
volcanic eruptions which laid the foun-
dations for this and the neighboring
islands.
The great mountains of that time
extended far beyond the confines of the
present island, probably uniting this re-
gion with the main land on the south.
Slowly these mountains were worn
down again by the weather and the
streams during vast periods of time,
until only the stumps remained be-
hind. and then this worn-down noun
tain country gradually disappeared be-
meath the waves of the great sea of
early Tertiary time. Then for long
ages only shells of marine organisms
of various types accumulated over the
site of these vanished mountains, build
ing up the limestone beds, several
thousand feet in thickness, which now
constitute the greater portion of the
island west Of the Blue mountain
ridge.
When these limestones had thus
formed by the slow accumulation of the
shells of marine animals, they were
again raised above the sea level, and
to a much greater height than that at
which we find them now. This was the
result of a second great disturbance of
this region, accompanied by bending
and breaking of strata by earthquakes
and by deep-seated volcanic activities,
though no actual surface eruption took
place.
An AntilIean Continent
So great was the elevation of the
jamaican region at that time that it is
probable that a junction with Hayti
and with Southern Florida was effect
ed. This great Antillean continent was
actively eroded by streams and the
material worn away from it was de-
posted around the border of the land.
Many of the valleys of the island
probably trace their beginning back to
this period of great elevation. Slow
subsistence again set in and jamaica
once more appeared as an independent
island, with dimensions not unlike
those of the present time, AS subsi-