Illinois State Museum

Tropical Forest - Forces of Change

insect on plant
Illustration of Actions of Living Things

Forces of Change caused the land to emerge. The basic forces were:

Plate Tectonics - The plates carrying Illinois and northern Europe were colliding with the plates that carried the large continent of Gondwana. The force of this collision moved Illinois up and down and caused sea levels to vary over millions of years.

Glaciation - Expansion and contraction of glaciers in the southern hemisphere, along with tectonic activity, alternately raised and lowered sea levels, exposing and then flooding the area.

Evolution - New species were evolving to fill niches that emerged on dry land.

Actions of Living Things - Land plants changed the atmosphere by taking in carbon dioxide and releasing oxygen.

What's Here—What's Not?
There were plants and animals on land. Large tree-like ferns and other tropical plants grew on land and in swamps. Land animals included scorpions, spiders, giant dragonflies, large archaic amphibians, and reptiles. Marine animals lived in the shallow seas. Grasses, other flowering plants, mammals, and birds had not yet evolved.