Rocky ledges jutting forth to form stony outcrops along -Iowa's streams, roadcuts and hillsides provide evidence of ancient environments entirely different from the rolling prairies of today. These rocky ledges were laid down in the bottoms of vast shallow seas which covered most of Iowa in its past history. Over great lengths of time, the waters swept back and forth, rising and subsiding, leaving a record in the layers of the earth's materials deposited in their depths. As the seas rose and fell, the deposits buried one another and became layers of conglomerate, sandstone, shale and gypsum. Minerals of calcite, dolomite, pyrite, galena glauconite and many others formed in these strata. Fossil remains of the plants and animals which lived in these environments left a record of life that flourished in these early seas. One distinctive form of animal life was the trilobite.
Iowa Science Teachers Journal
© Copyright 1980 by the Iowa Academy of Science
Brown, Joseph H.
"Trailing the Trilobite,"
Iowa Science Teachers Journal: Vol. 17
, Article 15.
Available at: https://scholarworks.uni.edu/istj/vol17/iss3/15