Mexico weekly ledger., 1876-10-19
The Origin of the Great Lakes.

AT the meeting of the Scientific Asso-
citation in Buffalo, a paper was read by
Prof. j. 5. Newberry, of Columbia Col
lege, attempting to explain the origin
of the Great Lakes of this country. He
states that the sequence of vents in
the formation of the Great Lakes seem
to have been somewhat as follows:
l. The Laurentian belt north Of the
| Great Lakes, which has been a land
surface since the beginning of the
Paleozoic era, was formerly a high
mountain. range, the degradation of
which has supplied the mechanical ma
terials which compose the sheets of
Paleozoic rock that surround it. The
erosion of these highlands has continu-
and was specially rapid during the
period.
2. Previous to the glacial period, the
elevation of this portion of the Cont
nent was considerably greater than now,
and it was drained by q river system
which flowed at a much lower level than
at present. At that time our chain of
lakes-Ontario, Erie and Huron-ap-
parently formed portions of the valley
of a river which. subsequently became
the St. Lawrence, but which then flowed
between the Adirondacks and Appala-
chians, in the line of the deeply buried
channel of the Mohawk, passing through
the trough of the Hudson, and empty
ing into the ocean 80 miles southeast of
New York. Lake Michigan was appar-
emily then a part of a river course
which drained Lake Superior and emp
tied into the Mississippi, the Straits of
Mackinaw being not yet opened.
3. With the approach of the cold pc
riod, local glaciers formed on the Lauren
tian Mountains, and, as they increased
in size, gradually crept down on to, and
began to excavate, the plateau which
bordered on the west and south. The
excavation of our lake-basins was be-
gun, and perhaps in large part effected,
in this epoch. -.
4. AS the cold increased and reached
its maximum degree, a great ice-sheet
was formed by. the enormously in
creased and partially coalescing local
glaciers of the former epoch. This
man-lobed ice-sheet, or compound gla-
cier, moved radiatingly from the south,
southwest, and western slopes of the
Canadian highlands; it's Ohio lobe
OoSAAALAS uo q GOuUh os SIILlIlh1Vis
The effect of this glacier upon Lake
Erie and Lake Ontario would be to
broaden their basins by impinging
against and grinding away, with incon-
ceivable power, their southern margins.
5. With the am~elioration of the eli
mate the Widespread ice-sheets of the
period of intensest cold became again
local glaciers, which completed the al
ready began work of cutting out the
lake-basins., Atfirst the glaneier which
had before flowed over the water shed
in Ohio was so far reduced as to be un-
able to overtop it's summit, but, defect
ed by it, it flowed along it's base, spend
ing its energies in cutting the shallow
basin in which Lake Erie now lies.
6. The melting of the glaciers was
accompanied, perhaps occasioned, by a
sinking of the Continent, which pro-
crossed until the waters. of the Atlantic
flowed up the Valley of the St. Lawrence
to Kingston, and up the Ottawa to
Arnprior. The Valleys of the St. Law
renee and the Hudson were connected
by way of Lake Champlain, and thus
the highlands of New England were left
as an island. 1t is also possible that
the sea-water penetrated t o the lake
basin through the Valley of the Mo-
hawk and through that of the Missis- |
sippi, buS of this we have no evidence |
in the presence of marine fossils in the
surface-deposits. The great area of
excavation in which the lakes lie was
probably At this time filled to the brim
with ice-cpld fresh water.