St. Landry democrat. (Opelousas, La.) 1878-1894, 1888-07-28
THE GREAT LAKES.
Geological History of Their Formation and
Change in Their Level.

Change in Their Level.
Promising that lakes are destroyed
by rivers, by the double process OF
filling them up with sediment and
of deepening the channel of escape,
and that, on the other hand, lakes are
formed chiefly by the upheaval OF the
earth's surface and by its erosion by
the movements of glaciers, the author
devotes the greater part of his article
to the geologic history of the forma~
ton of the great lakes. Their beds,
with the possible exception OF Erie,
were secured out of solid rock by
the great glaciers of the ice age, but
accumulation of debris in many cases
increase their depth and influence the
direction of their outflow. The removal
of this debris, in the case OF the
Erie, for instance, would reduce it
greatly, perhaps entirely drain it, and
would make it flow into Ontario and
Hamilton. The increase of heat caused
the edge of the great glacier to retract
from the southern border at Fort
Wayne, where the water generated
upon it flowed into the Wabash, and
separated Erie and Ontario into two
lakes. But as long as the ice remained
in the St. Lawrence valley the waters
found their escape into the Mohawk al
Rome. One of the beaches formed by
the action of the waves has its crest
marked by the ridge road from Lewis.
ton to Sodus. At this time Lake Erie
was only one-third as long as now, and
its surface was only one-fifth as great,
Toledo, Cleveland and the Bass Islands
being far inland. When Lake Ontario
forced a new output through the st.
Lawrence valley its level was drawn
down five hundred feet and its area
reduced ninety per cent, becom'
ing thirty per cent. smaller thar
at present. The rising of the
depressed land to the northward gave
the lakes their present dimensions, ano
the oscillation then received a check.
"a further fitting of the land to the ex.
tent of three inches in each mile would
send a great river from Chicago to the
Mississippi, reverse the current in the
Detroit, stop Niagara Falls and rot
the upper St. Lawrence of seven.
Fights of it's water" Whether, con.
trary to what appears to be law against
absolute stability, the oscillation has
entirely ceased or not, it is now sc
slow as to prevent the detection of any
the present level of the
water having remained nearly con-
slant for many centuries.
Other changes are, however, in
from the action of the rivers.
The St. Clair is feebly securing its
channel and building it's delta; the Nj
agara is eating its way back to Lake
Erie; the St. Marie, Detroit and St.
Lawrence are deepening their chan
nels. ''All these processes are too
slow to affect our hopes and fears con-
corning the immediate future, and for
our posterity in the year 10000 We
have no solicitude. The men who
shall watch the draining of Lake
Erie-or who, perchance, shall find it
worth their while to prevent twill
as far surpass us in powers and re-
sources as we surpass the men who
the lakes creation. For all |
practical purposes our inland seas are
permanent, and their basins stable. |
The only notifications that affect our
are those wrought by the |
waves upon their coast" The changes |
in the water levels that are noticed are
due to the variations in the rainfall |
upon the lakes themselves and upon |
,he land drained by the streams that |
pour into them. The amount of rain.
all varies from year to year and |
rom one season to another in the
same year, and the level of the |
water oscillates around an average
position that remains fixed. Thus
Turing the period from 1860 to 1887,
he mean average range of Lake
Erie was 1.6 feet, and the extreme
'ange for the same period 3.5 feet. II
1888 Lake Erie rose Is inches above its
high stage, and in 1919 it fell
y feet below its usual plane. .'The
present low water is the sequel of last
drought" the lake region
having received only about rs inches o.
'ainfall instead of it's usual SO inches
This should cause fall of the lakes o:
about IA inches, half from direct loss
and half from the loss of the streams
hat empty into them. But the average
all of all the lakes was only about
inches, owing probably to the GOODNESS
II the autumn, which retarded evapo.
alton. In Lake Superior the fall was
inches below the average low stage,
he lowest point reached in seventeen
ears, except on two occasions. In
erie it was inches below the average.
These variations relate to the entire
urfaces of the lake. A part of one
nay be depressed and another part
aised by a gale especially in the
ase of Lake Erie, on account of its
hallowness. A gale has been known
o raise the level of one of it's ends
even or eight feet and to depress the
ther to an equal amount. Differences
n atmospheric pressures also effect
ifferent parts of the same lake. The