DESCRIPTION:
This is a brief overview of the last glacial period and human migration
route from Asia.
The last glacial period, popularly known as the Ice Age, was the most
recent glacial period within the current ice age occurring during the
last years of the Pleistocene, from approximately 110,000 to 12,000
years ago. Scientists consider this "ice age" to be merely the latest
glaciation event in a much larger ice age, one that dates back over two
million years and has seen multiple glaciations.
During this period, there were
several changes between glacier
advance and retreat. The
maximum extent of glaciation
within this last glacial period was
approximately 22,000 years ago.
While the general pattern of
global cooling and glacier advance
was similar, local differences in
the development of glacier
advance and retreat makes it
difficult to compare the details
from continent to continent
From the point of view of human archaeology, it falls in the Paleolithic
and Mesolithic periods. When the glaciation event started, Homo
sapiens were confined to Africa and used tools comparable to those
used by Neanderthals in Europe and the Levant and by Homo erectus
in Asia. Near the end of the event, Homo sapiens spread into Europe,
Asia, and Australia. The retreat of the glaciers allowed groups of
Asians to migrate to the Americas and populate them.
The end of the last glacial period was about 10,500 BCE. The last
glaciation centered on the huge ice sheets of North America and
Eurasia. Canada was nearly completely covered by ice, as well as the
northern part of the United States, both blanketed by the huge
Laurentide ice sheet. Alaska remained mostly ice free due to arid
climate conditions. Local glaciations existed in the Rocky Mountains
and the Cordilleran ice sheet and as ice fields and ice caps in the
Sierra Nevada in northern California.
Wisconsin glaciation
The Wisconsin Glacial Episode was the last major advance of
continental glaciers in the North American Laurentide ice sheet. At the
height of glaciation the Bering land bridge potentially permitted
migration of mammals, including people, to North America from
Siberia.
It radically altered the geography of North America north of the Ohio
River. At the height of the Wisconsin Episode glaciation, ice covered
most of Canada, the Upper Midwest, and New England, as well as
parts of Montana and Washington. On Kelleys Island in Lake Erie or in
New York's Central Park, the grooves left by these glaciers can be
easily observed. In southwestern Saskatchewan and southeastern
Alberta a suture zone between the Laurentide and Cordilleran ice
sheets formed the Cypress Hills, which is the northernmost point in
North America that remained south of the continental ice sheets.
The Great Lakes are the result of glacial
scour and pooling of meltwater at the rim of
the receding ice. When the enormous mass
of the continental ice sheet retreated, the
Great Lakes began gradually moving south
due to isostatic rebound of the north shore.
Niagara Falls is also a product of the
glaciation, as is the course of the Ohio
River, which largely supplanted the prior
Teays River.
With the assistance of several very broad glacial lakes, it released
floods through the gorge of the Upper Mississippi River, which in turn
was during an earlier glacial period.
In its retreat, the Wisconsin Episode glaciation left terminal moraines
that form Long Island, Block Island, Cape Cod, Nomans Land, Martha's
Vineyard, Nantucket, Sable Island and the Oak Ridges Moraine in
south central Ontario, Canada. In Wisconsin itself, it left the Kettle
Moraine. The drumlins and eskers formed at its melting edge are
landmarks of the Lower Connecticut River Valley.