, 1876-12-08
The Origin Of the Great Lakes.

At the meeting Of the Scientific Asso-
c;ation in Buffalo n paper was read by
prof. J. =. Newberry attempting 10 ex-
.plain the origin Of the great lakes Of this
country. He states that the sequence Of
events in the formatioDy~of the great
lakes seems 10 haveC5een somewhat as
follows:
1. The LaurcntiAn belt north Of the
great lakes, which has been land sur
face since the beginning Of the Palr-
ozoic era, was formerly n high mountain
range. the degradation of which has sup
plied the mechanical meterials which
compose the sheets Of Palnozoic rock
that surround it. The erosion Of these
highlands has continued uninterrupt-
edly till the present day. and was spe-
ciaily rapid during the period.
,. Previous to the glacial period, the
elevation of this portion Of the continent
was considerably greater than now, and
il was drained by a river system which
flowed o, n much lower level than at
present. At that time our chain Of lakes
Ontario, Eric and Huron-apparently
formed portions Of the valley Of a river
which subsequently became the st.
Lawrence, but which then flowed be-
tween the Adirondacks aud Appala-
chians, in'the line of the deeply buried
channel of the Mohawk, passing through
the trough of the Hudson, and emptying
into the ocean eighty miles southeast Of
New York. Lake Michigan was appar-
emily then part of river course which
drained Lake Superior and smptied into
the Mississippi, the straits of Mackinaw
being not yet opened.
3. With the approach of the cold period
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.
f. As the cold increased and reached
its maximum degree a great ice sheet
was formed by the enormously increas-
ed and partially coalescing glaciers of
the former epoch. This many lobed ice
sheet, or compound glacier, moved radi-
atingly from the south, southwest and
western slopes of the Canadian high
lands; its 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 inconceivable power, their south.
ern margins.
5. With the amelioration of the eli
mate the widespread ice sheet of the
period of intensest cold became again
local olaciers which cou1nletad the al
ready begun work of cutting out the
lake basins. At first the glacier, which
had before flowed over the watershed in
Ohio, was 80 far reduced as to be unable
to overtop its summit, 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
sinking of tbe continent, which pro-
gressed until the water of the Atlantic
flowed up the valley of the St Law
renee to Kingston, and up the Ottawa to
Arnprior. 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 though that
OF the Mississippi, but of this we have
no evidence in the presence Of marine
fossils in the surface deposits. Tho
great area Of excavation in which the
lakes lie wos probably at this time filed
to the brim with ice-cold fresh water.