Did we know Nebraska Sand Hills is due to the Ice Age receeding? I googled this and here’s a bit of what I found.
The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, and the Western Interior Sea) was a large inland sea that existed during the mid- to late Cretaceous period as well as the very early Paleogene, splitting the continent of North America into two landmasses, Laramidia to the west and Appalachia to the east. The ancient sea stretched from the Gulf of Mexico and through the middle of the modern-day countries of the United States and Canada, meeting with the Arctic Ocean to the north. that completely separated the North American continent?
So when we speak of the Sand Hills of Nebraska, we now know why there’s big sand in the middle of a land-locked state.