Sand Hills, United States
As the largest sand dune formation in America, the Sand Hills cover about a quarter of the U.S. state of Nebraska. These ancient sand dunes are from the Pleistocene Epoch (1.8 million to about 10,000 years ago). They are made of sediment eroded from the Rocky Mountains by glaciers, washed out into the plains, and now mostly stabilized by grassland vegetation. This 2001 Terra image
shows a portion of the Sand Hills region, the landscape rippled by crowded yellow-tan and lavender-brown dunes. The area does not drain water well, so the hollows at the bases of dunes are filled with brilliantly blue lakes. The sandy soils were not attractive to farmers, and the area was left largely unplowed by European settlers. Today, the area is being cultivated as seen in some of the emerald green vegetation in the image. Perfect circles of vegetation resulting from centerpivot
irrigation appear in the scene, as well as fields with sharp angles and straight lines. The area is an important habitat for migratory birds.