Nebraska's landscape is dominated by surface features, soil and aquifers in loosely compacted sediments, with areas of the state where thick layers of sedimentary rock outcrop.
Tectonics researcher Christoper Scolese suggests that vast inland seas inundated much of southern and western Nebraska ten million years before the start of the Carboniferous rainforest collapse and the mass die off of many large amphibians.
Shale, limestone and sandstone mark the Permian rocks of this period along with gypsum and halite deposits that suggest rapid desiccation in an arid climate.
Nebraska transitioned to terrestrial conditions by 275 million years ago (Ma), with limited marine activity, coal swamps and paleosols preserving the climate of the period.
In the early Cretaceous, Nebraska received up to 100 inches of rain a year because of high temperature conditions, at nearly three times the present rate of precipitation, carrying sediments through meandering rivers in a coastal plain and depositing them in the Western Interior Seaway.
Between 88 and 80 million years ago (Ma), the Niobrara Formation formed, rich in chalk from marine plankton as well as shells and fish bones, tied to the same expansion of seas that left the earlier shales and limestone.
During the Paleocene and the Eocene, Nebraska experienced a warm, humid climate and gathered sediments shed from the uplifting Rocky Mountains.
With the onset of the Quaternary and Pleistocene glaciations, Nebraska remained free of ice sheets but experienced harsh climatic conditions typical of a polar desert or taiga, while continuing to receive sediments from further west.
The arrival of humans in the Holocene began to alter the surficial geology and hydrogeology of Nebraska, particularly since the advent of statehood, with widespread agriculture.