The Jeffersonian. [volume] (Stroudsburg, Pa.) 1853-1911, 1876-11-09
THE ORIGIN OF THE GREAT LAKES.

At the meeting of the Scientific Asso-
cation IN Buffalo paper was read by Prof.
q. d Newberry, attempting to explain the
origin of the great lakes of this country.
he states that the sequence of events in
the formation of the great lakes seems 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 PaIeozoic era,
was formerly high mountain range, the
degradation of which has supplied the me-
chanlcal material which composes the sheets
OF Paleozoic rock that surround it. The
erosion of these highlands has continued
uninterruptedly till the present day, and
was especially rapid during the period.
Z Previous to the glacial period, the
elevation of this portion of the Continent
was considerably greater than now, and it
was drained by river system which flows
at much lower level than at present. At
that time our chain of lakes-Ontario. Erie
and Huron-apparently formed portions of
the valley of river which subsequently,
became the st. Lawrence, which then flowed
between the Adirondacks and Appalach-
lans, in the line of the deeply buried chan
mel of the Mohawk, passing through the
trough of the Hudson, and emptying into
the ocean eighty miles southeast of New
York. Lake Michigan was apparently
then part of a river course which drained
Lake Superior and emptied into the Mis-
sissippi the straits of Mackinaw being not
yet opened.
2 With tho onnrooob &c ~ = LII -: !
local glaciers formed on the Laurentian
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 begun, 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 increased and
partially-coalescing local glaciers of the for
mer epoch. The many-lobed ice-sheet, or
compound glacier, moved rapidly from the
south, southwest and western slopes of the
Canadian highlands It's Ohio lobe reaching
as far south as Cincinnati The effect of
this glacier upon Lake Erie and Lake Onta-
rio would be to broaden their basins by
impinging against and grinding away, with
uncomfortable power, its southern margins
5. With the amelioration of the climate
the wide spread ice sheet of the period of
the intensest cold became again local gla-
ciers, which completed the already begun
work of cutting out the lake basins. At
first the glacier, which had before flowed
over the water shed in Ohio, was so FAR re-
duced as to be unable to overtop It's SUM
NIT, but, detected by it, it flowed along its
base, spending its energies in cutting the
shallow basin in which Lake Erie now lies
6. The melting of the glaciers was ac-
companied, perhaps occasioned by a sink
ing of the Continent, which progressed un-
til the waters of the Atlantic flowed up the
Valley Of the St. Lawrence to Kingston,
and up the Ottawa to Arnprior. The Val
leys of the St. Lawrence 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 to the lake
basin through the Valley of the Mohawk
and through that of the Mississippi, but of
this we have no evidence IN the presence of
marine fossils in the surfaee-deposits. The
great area of excavation in which the lakes
lie, was probably filed to the brim at this
time with ice-cold fresh water.