In terms of geology, 10,000 years is the same as a blink of an eye
in a lifetime. However, there have been many changes in what is now
Illinois, compared to what it was that long ago.
Imagine going back to that time. The climate has just begun to warm
up, after experiencing a period when glaciers entered the state. Ice
sheets are still as close as southern Canada. The Great Lakes are beginning
to form as the ice continues to melt. The Illinois River is a relatively
new river, especially in the northern part of the state. The lower part
of the Illinois River has taken the place of the ancient Mississippi
River, which moved farther west during the glacial advance.
The type of plants in Illinois is changing from sparse tundra (a cold
semi desert) to grasslands in the northern part of the state, and from
spruce to oak-hickory forests in the southern part of the state. Because
these changes were occurring so quickly, some scientists believe many
living things could not adapt. They had to move to other areas, or cease
to exist around this time.
There were several types of animals present then that can no longer
be found in this area. Some have become completely extinct.
Two large animals that inhabited the Midwest, Mammoths and Mastodons,
are examples of two creatures that could not survive the changes that
were taking place.
Mammoths were much like today's elephants that are found in Africa
and India.
Mastodons, while looking much like an elephant, were different in several
respects (see Mammoths and Mastodons).
Other large animals that were present included ground sloths, giant
beavers, and bison.
As the climate continued to warm, ecosystems changed. An Ecosystem
is an interacting community of organisms and their environment.
New plants took over areas previously dominated by cold weather plants.
Animals that had previously relied on these plants for food had to move
to other locations, which meant that predators that relied on these
animals for food had to move as well. Sometimes there was no place that
provided satisfactory food and shelter. Eventually, many of the Ice
Age animals became extinct.
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