|
|
A prairie is a type of grassland. The name comes from the French word for "meadow." You may have heard of the steppes in Asia, the pampas in South America or the veldt in Africa. These are all grasslands, too. Grasslands cover about one-fourth of the earth's surface and are the largest habitat in North America.
Prairies usually form on level or smoothly rolling landscapes. These areas have a dry or cold season that kills the plants so that they can burn. Most of the prairies in North America developed in places where the amount of rainfall each year is low. The Illinois prairies receive enough rain to support large trees. Frequent fires stop trees from overcrowding prairie plants.
HOW DID THE ILLINOIS PRAIRIES FORM?
Most of the land in the northern two-thirds of Illinois is flat. The land took this shape after glaciers moved through. These giant walls of ice formed and spread at a time when the climate in North America was much colder than it is now. The massive weight and grinding action of the glaciers pushed the soil and flattened it. Four major glaciers covered parts of Illinois during this period which ended about 12,000 years ago. One of the glaciers, the Illinoian, moved south to Carbondale in southern Illinois. This was as far south as any glacier in the United States reached at this period of glaciation.
The weather conditions in Illinois over thousands of years helped determine that prairies would exist in Illinois. The climate of the prairies is characterized by hot, dry summers and cold winters. When these conditions developed about 8,300 years ago, the tallgrass prairie became a major part of Illinois.
As the climate warmed and the glaciers began to melt, huge amounts of water flowed from them. These moving waters helped to form today's river valleys, especially of the large rivers in Illinois, like the Illinois and Mississippi. The waters also carried lots of sand and gravel. This load of rocky material was dropped to the river bottom when the river current slowed. Eventually the glaciers produced less water and the rivers became smaller. Some of the material carried by the rivers was now out of the water. Along the Illinois, Mississippi, Green and Kankakee Rivers, sand prairies were formed by this process.
CELEBRATE THE PRAIRIES!
The third full week in September is celebrated as "Prairie Week." This annual event occurs thanks to a law passed by the legislature. The purpose of the observance is to develop in people an appreciation of prairies. Many activities are conducted during this time in places like parks and nature centers. Demonstrations on how to develop prairies and nature walks through prairies are some of the events in which you might want to participate.
|
|
