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History of Nebraska

  • 24 min read
  • 12 chapters

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Through Invertebrate, Fossil and Skeleton

Prehistoric

Mesozoic

During the Late Cretaceous, between 66 million to 99 million years ago, three-quarters of Nebraska was covered by the Western Interior Seaway, a large body of water that covered one-third of the United States. The sea was occupied by mosasaurs, ichthyosaurs, and plesiosaurs. Additionally, sharks such as Squalicorax, and fish such as Pachyrhizodus, Enchodus, and the Xiphactinus, a fish larger than any modern bony fish, occupied the sea. Other sea life included invertebrates such as mollusks, ammonites, squid-like belemnites, and plankton. Fossil skeletons of these animals and period plants were embedded in mud that hardened into rock and became the limestone that appears today on the sides of ravines and along the streams of Nebraska.

Cenozoic

Pliocene

As the sea bottom slowly rose, marshes and forests appeared. After thousands of years the land became drier, and trees of all kinds grew, including oak, maple, beech and willow. Fossil leaves from ancient trees are found today in the state's red sandstone rocks. Animals occupying the state during this period included camels, tapirs, monkeys, tigers and rhinos. The state also had a variety of horses native to its lands.

Pleistocene

During the last ice age, continental ice sheets repeatedly covered eastern Nebraska. The exact timing that these glaciations occurred remain uncertain. Likely, they occurred between two million to 600,000 years ago. During the last two million years, the climate alternated between cold and warm phases, respectively called "glacial" and "interglacial" periods instead of a continuous ice age. Clayey tills and large boulders, called "glacial erratics", were left on the hillsides during the period when ice sheets covered eastern Nebraska two or three times. During various periods of the remainder of the Pleistocene and into the Holocene, the glacial drift was buried by silty, wind-blown sediment called "loess".

Holocene (present-day)

As the climate became drier grassy plains appeared, rivers began to cut their present valleys, and present Nebraska topography was formed. Animals appearing during this period remain in the state to this day.

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