|
Geology of Iowa: Iowa's Earth History Shaped by Ice, Wind, Rivers, and Ancient Seas Iowa’s geologic history lies buried beneath the ground. The deeper, older and least frequently seen portions of this history consist mostly of sedimentary rocks such as sandstone, limestone, dolomite and shale, which are over 3,000 feet thick in places. These rocks originated as layers of loose sediment accumulating in shallow seas and along coastal and floodplain environments that occupied Iowa between 74 million years ago (Cretaceous) and 530 million years ago (Cambrian; see map, below). With time, this sediment hardened into rock containing fossil remains of past animal and plant life. Fossil-bearing rocks are found among the abundant outcrops of northeastern Iowa, a topographic region called the Paleozoic Plateau (see Landform Regions map, bottom). Also, bedrock is occasionally exposed along the state's river valleys, at roadcuts, and in quarries. |
||||||
|---|---|---|---|---|---|---|---|
| more> | |||||||
