Fossils found in this area show that from 350 to 570 million years ago, a shallow sea covered the Midwest.  North America was south of the equator then, and many prehistoric corals, sharks and huge fish lived in our warm tropical seas.  Fossils from this ancient ocean are fairly common because the rock layers where these fossils are found are not as deep here as in other parts of the state.
Ancient Ocean Fossils
	About 300 million years ago, our area was part of the newly developing super continent, Pangea. The Appalachian Mountains had formed and the Midwest was then a tropical forest of fern trees, horse tails and club moss.  Large amphibians, small reptiles and bird-sized insects evolved. Still near the equator, the land that would be Illinois was warm and swampy.
Ancient Fern Fossils
The Ice Ages began about two million years ago and carved our current landscape.  Glaciers also moved the Mississippi and Rock Rivers into their present locations.  The ancient Mississippi once flowed east of where it does today, winding south of here near Princeton, IL.  Geologists believe the ancient Rock River once flowed almost straight south, but was  blocked by glaciers and pushed into its present course between Lyndon and Prophetstown.

Home page

Next page