The San Francisco call., 1904-02-16
Earth Movements.

Copyright 1904 by Joseph B. Bowles)
The level Of the ocean is more con-
start than that Of the land. The ex-
parse Of the ocean is three times IS
great as that OF the land, and its depth
more than ten times as great If all
the land should be sunk in the ocean,
II would raise the general water level
or1v about 800 feet In general We
may say with perfect confidence that
the ocean beds represent portions of
the earth's crust which have been
sinking from the earliest geological
times. while the continents represent
those portions which. with many os-
citations. have. on the whole, been
rising. Tt probably is not true. as is
often stated. that the areas Of land
and water have shifted places in past
time so that continents were found
whore the main ocean beds now lie,
and oceans swept without interruption
o.-er the continental areas. Still
there is the best Of evidence that
large portions of the existing conti-
reuts were at various times below the
level Of the sea
But while this is true, II seems
equally certain that during the sub
si6ence of these areas below the sea
level they existed either as shallow
uater borders of the main continental
areas or as internal seas. For exam
Ile. the great depth of sedimentary
rocks which cover the Mississippi ba-
sin. extending from the Allegheny
Mountains 10 the Rocky Mountains,
are shallow water deposits. So shall
low. indeed. was the water during long
periods that il was little more than
swamp in which the vegetation that
formed the numerous seams Of coal
couId grow and flourish. But the lev
el was not constant. After a large
arcunulation Of vegetable matter that
could be turned into coal had taken
place there was q slight and very gen
tie sinking of the whole area, so that
mud and sand were brought in from
the neighboring higher lands to form
q complete covering for the coal; so
that when il was turned into rock it
was able 10 protect il and preserve it
for future ages. This process Of slow
but irregular sinking Of the Mississippi
basin continued until thousands of
feet Of sedimentary material had been
washed into it, as the Mississippi is
carrying sediment into the Gulf Of
Mexico at the present time. These
successive strata, like the leaves of a
book. record the various downward
movements Of the long coal period.
In other countries, especially in Eng
land and China, there is the same rec
ord OF long continued downward
movements Of continental areas during
the coal period.
If this downward movement had con-
inaccessible beneath the depths Of the
sea. where, indeed. much Of it does still
remain. In Nova Scotia the best seams
of coal are mined many miles and at
depth Of many hundred feet below the
bottom Of the sea In England also
some Of the best seams Of coal are fol-
lowed out underneath the sea, and it
is supposed that coal veins are con-
tinuous from southern England to the
Continent far beneath the bottom Of
Dover Strait. But fortunately the
downward motion Of the coal area was
in due time arrested. and the contrary
movement begun, which has brought
this priceless material within easy
reach II men in the mountains Of Penn
syivania and China, in the hills of Eng
land and in the plateaux Of the cen
tral and western States OF America
Cther illustrations Of great changes in
lend levels are too numerous TO be men,
Toned in detail In Colorado there was
q gradual subsidence Of land below sea
level during the carboniferous and Gre
taceous areas until from 1000 TO $1,000
feet of sediment had accumulated over
the sinking area. But at the end Of
that period the area began 10 rise and
this rise has continued until the present
4 time, when il stands many thousand
feet above the level Of the sea.
similar witness 10 such changes Of
level is borne by extensive sedimentary
rocks containing abundant sea shells
Of late geological age. which are found
at a height Of 10000 feet above the sea
OF the Pyrenees, the Alps and the eau
casus mountains, and at a height Of
1900 feet upon the mountains OF. Cen
tral Asia. A map of the eastern con-
tinent during the early part Of the ter
tiary period shows a great Mediter-
ranean Sea covering all Central Furopa
ard extending into Asia, submerging
the highlands Of Thibet and most of
the mountains Of Turkestan. But that
this was not a general subsistence Of
the continents is evident from the sim
PIE fact that these areas are covered
with sedimentary strata. II mud and
sand and gravel are deposited in water
there must be some area not far awaS
from which they could be derived.
While these general facts concern
ing changes in land level in ancient
geological times beyond all question
arc very impressive. less attention than
they merit has been given to the facts
showing that corresponding changes
are 9tiil going on, and have produced
striking results within recent times.
and point TO interesting conclusions
with reference to the future. In con-
nection with the glacial period. which
Is tho most recent Of All the geological
epochs. these changes of level are very
evident and connect themselves with
the early history Of mankind. At the
close If the tertiary period. which
eliminated in the glacial ers- the CEN