|Ice Ages||ISM Home > Exhibits > Ice Ages|
The amount of ice on the Earth's surface has varied greatly through time. For example, the extent of ice in North America has changed dramatically since the height of the last glacial advance 20,000 years ago.
During most of the last 1 billion years the earth had no permanent ice. However, sometimes large areas of the globe were covered with vast ice sheets. These times are known as ice ages. Illinois has experienced changes in rocks and fauna during these times. This Web module tells how some of these changes happened. Knowledge of the changes and their causes helps increase understanding about ancient rock formations and animals remains found in Illinois sites as evidenced in the Museum's specimen collections and site reports.
For example, the Online Exhibit The Midwest 16,000 Years Ago presents evidence that snowshoe hares are found today in the northern part of the midwest, yet 16,000 year old remains were found in Kentucky and Missouri, much farther south. If a type of animal lives in a certain type of climate now, we may infer that its ancestors lived in that type of climate, too. Does that mean that Kentucky and Missouri were once as cold as Wisconsin is today? What other evidence can we study to find out?
To begin to understand ice ages we must answer the following questions:
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