The Anderson intelligencer. [volume] (Anderson Court House, S.C.) 1860-1914, 1903-03-18
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Thickness Of Ehrth's Crust Over The
United States.

- SoOhS ooLA 40
trying to answer that question. His
experts have been engaged recently in
measuring the thickness Of the earth's
crust in various parts Of the United
States and they find that itvaries very
much. The rind of the planet be-
meath the city Of Charleston is about
twenty-five miles through; at Iankton,
South Dakota, it is only about half as
thick as that.
The crust is found to be thiokest
along a belt which passes through the
eastern portion Of the United States,
around by the southeast. and through
the middle south. 1t thins off toward
the north and west, and appears to be
thinnest on the plains Of South Dako-
ia, where the fiery core Of the globe
m so close to the surface that the
Artesian wells are all tepid, one such
At Pierre supplying q swimming pool
that has a natural temperature Of so
degrees.
1t used to be supposed that the
earth's crust was Of u fairly uniform
thickness everywhere, but this notion
has been exploded by DR.. Nelson Fl.
barton, of the United States geologi-
cal survey, who has been engaged for
some time past in making temperature
observations at great depths in mines,
in wells, and in borings for oil and
gas. There are in the United States
quite q number of such borings which
60 down half q mile or more; there is
n at Wheeling, W. Va, throe.quar-
ters Of q mile deep, and another at
Pittsburg is considerably over a mile
in depth. Thus it has been practi-
cable to get down pretty far into the
she'll of the globe.
The accepted notion hitherto has
been that the temperature gained l
degree FOR every Fifty feet going down.
So it does in some places, but the rate
of increase varies enormously. Near
Yankton, South Dakota, it is l degree
for every seventeen feet: in the Calm
met and Hecla mine (Lake Superior)
it is only l degree for every 224 feet.
If it be asked why the earth's crust is
80 cool in the neighborhood Of Lake
Superior, the answer is that all the
region there is still chilled by the
glacial ice cap which anciently cover
ed it. This chill left behind by the
vanished ice cap appears T. extend
downward toa depth Of two or three
miles.
In eny given place the increase Of
temperature going down is constant,
and it only requires a little figuring to
ascertain at what depth in that par
tioular spot the rocks must be molten.
Such q condition Of things must exist
twenty-five miles below the city Of
New York, and it must be the same
way thirteen miles below Yankton.
The entire crust OF the earth is rela-
lively .hin, being much less &c thick
ness than the shell Of an egg, proper
tionately. Owing to the tremendous
pressure, the hot rock stuff beneath,
which would be fluid under ordinary
circumstances, is held as rigid as so
much steel; but once in e while there
comes q crack in the rind Of the planet,
and out COWS the molten rock. Such
OF occurrence is called q volcanic out
break and fluid rock is termed lava.
The water in q we'll so feet deep re-
mains at the same temperature all the
year around. If you wish to ascer-
tain the mean annual temperature in
in any locality take q bucket of water
from such q well and put q thermom-
eter into it. In the latitude Of New
York this temperatare is in the neigh,
borhood Of 60 degrees. After you get
down into the earth 1000 feet or 80
the Thermometer begins to rise, show
ing the efeotof the su~bterranean heat,
and it continues to go up steadily. If
1t were practicable to bore holes deep
enough the. molten material from
below would doubtless rush up aud
out, creating az artificial volcano on g
small scale.
In parts Of the west remains of for.
mer volcanic conditions still exist in
the shape Of masses Of rocks near the
surface, which have not yet cooled of.
Such o state Of affairs is accountable
for the temperature Of the famous Hot
Springs of Arkansas; it is likewise the
case in the Yellowstone Park. Beneath
the celebrated Comstock Mine, in
Nevada, there is a focus of volcanic
heat not more than four miles from
the surface Of Q ground, and con-
sequently the excavation of the great
lode has been attended by e~xtraordin-
ary ~difioulties, immense volumes Of